There both more factors involved, and more reasons for stiffer suspension. A major factor not discussed are the shocks. In the example above, the rate of wheel movement towards the ground (for the dip) did not factor in the shocks (rebound), nor did the bump example for the stiff spring. It is complicated. Beyond that, stiffer springs help prevent body roll/lean and help keep the tire flat to the ground. Soft springs allow the body to roll, which changes the effective camber of the tire. If you compensate by adding static negative camber, this sacrifices straight line braking... stiffer allows for less static camber. And, stiffer means generally less tire wear (which is a major factor in racing, either for cost or for stint length.) Finally, stiffer also is important for transitions from left turn to right (and vice-versa). Soft cars allow the body to roll from one side to the other and for that to be a large and slow transition. Stiff springs prevent the roll in the first place and switch to the other side faster. Stiffer tends to stabilize more quickly after sudden transitions. So, its quite complicated. There is no best. Generally, for smooth tracks, stiffer is better. Generally, for bumpy tracks, softer is better. (Those comments are to be taken relatively to each other.) Last but not least, driver preference/confidence vary a lot with how the car feels - some like stiffer/firmer (springs and shocks) and some like softer. So while the engineer may say one way or the other is technically or theoretically better, the driver may feel (and perform) better with a different setup. Thanks for considering a complicated and interesting topic.
"We have two cars driving. They're about to collide which is unfortunate..." This cracked me up. Probably because i am quite tired, but still, i thought it was funny that he found that worth mentioning. lol
+Khazar01 with the one caveat that you can't go too soft for bumpy roads or your suspension will bottom out and hit the bump stops. which is way worse than having suspension that's a bit too hard.
+Khazar01 Somewhat, but really not that simple. Bumpy is relative to speed. A road may seem very smooth at 30 mph, but the small hills become very meaningful at 150 mph. It may look smooth but if you're going fast enough it will make the suspension work more, but of course there are other factors you need to consider about speed (as mentioned at the end of the video).
I'm so confused with what kind of suspension to get in my car for Salt Spring Island. My wrx just started acting a bit like a marshmallow with a turbo strapped to it. Really awful B roads lots of roots ruts compression dips crests off cambered turns , pot holes etc. Rally suspension makes sense, except that I have road tires so that cancels that out. need to maintain grip when blasting around corners that want to knock you into a ditch, off a cliff or into a swamp.
I've always loved Colin Chapman's philosophy in car suspension design. Softer springs with long suspension travel always make for a better ride and better grip on rough roads. The main reason why mass production cars are given stiffer springs is because people have the tendency to rely on their perception that cars that roll are more likely to lose grip on a fast turn.
Cars that roll don’t handle as well, it’s a simple fact..also we don’t drive at freeway speeds in cars off road, he seems to forget suspension settings are able the road surface your driving on,which dictates the suspension settings which work best..off road a softer longer setting is best , on a road course it’s a different beast, and even then having a adjustable setup is best
Soft if you can handle the roll, since a soft suspension means grip. I've noticed that in some cars, just upgrading anti-roll bars and adding sticky tires improves the handling a much greater amount than when a lowered and stiffer suspension was added.
Unbearable Pain I disagree. Some people say the primary roll stiffness should come from the springs, not the sway bars. The sway bars reduce the independence of the suspension.
TassieLorenzo totally untrue... wheel indepenence ist not nessesarily a good thing. the myth that stiff suspension and hard dampers are a good thing comes from formula 1. in formula 1 you want the car to have the same attitude to the road at all times to maximize downforce. "mechanical grip" is irrelevant in F1. but since a roadcar has no downforce soft suspension will be better. thats also the reason why for example ralleycars have really soft suspension compared to for example f1 cars even when the are driving a tarmac ralley.
MrBusunglueck "but since a roadcar has no downforce soft suspension will be better. " Then why do road-based race cars with no downforce have stiff suspension? ;)... I agree there is such a thing as too stiff, but driving some road car on a track day with Hoosiers and using stock comfort-tuned suspension will give a terrifying wallowy feeling and feeling of lack of control. There is a REASON after all why PROPER sporty cars like Renault Megane RS, Civic Type R, Lancer Evolution, indeed Ferrari F430, etc all come with relatively stiff suspension.... surely? ;)
TassieLorenzo the thing is... racecars with no downforce dont have stiff suspension. the reason why all sportscars are stiff is cause thats what people want. the nurburgring laptime off the current 911 turbo s for example was set with the dampers in comfort mode. the nurburgring is a bumpy track, but still that says a lot for me.
2 more reasons why stiff springs work well on the track: 1. To give a driver better feedback with regard to surface changes or communicate tire compliance with the road. So if you hit a spot of gravel vs ice you can feel the changes. 2. Also with higher speeds on a track, impacts from road surface changes or even suspension movement due to braking or cornering causes more travel and uses suspension compliance forcing the shock to operate outside of it's optimum stroke. So stiffer suspension is needed in order for the components to handle higher speeds. Granted your tires still have to be good enough to generate the traction needed to allow for it's proper operation or you can loose more traction because of the loss of compliance.
If he wanted to bottom up design a car, I would help fund the dude. Guy should start a kickstarter collaborative with other car guys and design and build an affordable sports car that can be mass produced.
Why? He's just doing the same kind of engineering that's made at the factory. The output in that case would be a really nice, well engineered premium car, nothing out of this world.
Every time I watch your videos like this one, you just make me want to keep my car stock, and just learn how to drive what I have better. So thanks for saving me money lol.
I am a bit confused. If we are just looking at spring rate, why aren't we looking at a spring that has enough travel to reach the 20mm? In that case the stiff spring would win, the only reason it loses is because it runs out of travel and gravity has to do the rest as you mentioned. I guess the video is not about preloading the spring and the only source of compression is vehicle weight. If it was preloaded (as almost all passenger cars are, and why spring removal has to be done carefully even when the wheels are lifted off the ground), then the stiff spring should have ~10X faster ground contact in the dip. Your point is very valid on the bump force though.
davetek490 The amount the spring compresses is based on the weight on it. A stiffer spring will compress less, and thus have less travel. 10x faster ground contact? Nope, the math says otherwise (even in the portion where there is still travel remaining).
Engineering Explained For the sake of being devils advocate I'm assuming a preload to allow stiff spring to travel 20mm. The stiffer spring has higher F/mm.... if F=ma, then if both springs are allowed to travel the full 20mm, at every mm of travel, the stiffer spring has more force. if a=F/m and m is constant, a is linearly higher with respect to F. I must be missing something.
davetek490 The thing you're missing is that as the spring releases (look at the graph I drew) the amount of force it presses decreases (rapidly with a stiff spring, slowly with a soft spring). The maximum force both springs press is the same, but the soft spring will press with a greater force for longer (it does more work).
Engineering Explained Ok, and that's only true in the case where the only force used to preload the spring is the 1000kg car. I get you, I think we're just using different initial conditions. Thanks for the explanation.
davetek490 a soft spring will make the car bouncy when the mass of the car is moving, like when you go over a crest. to stop this you ned a shockobsorber to steady out the pressure on tyres to keap traction. does a soft spring not need a harder obsorber with gives a harder spring some advatage when it comes to travel? great explanation on springs, very intresting
4 those of u who didn't fully understand. What he has explained is the perfect formula to base a suspension set up "coilovers". Thanks to this man and his video I understand completely on how to set up my car the way I want it. There are an infinite amount of spring rate set ups. What it comes down too is your own style of driving to formulate a functional set up for both street and track "AutoX". I'm headed in that direction. I want the best of both worlds because math makes that possible. Thank you for your injenuity.
When you add the effects of compression and rebound dampening (oil damper), this gets much more complicated than just a spring with no damper. In fact, a spring alone does a terrible job of keeping the wheel on the ground. Playing with dirt bike suspension in the good old days of Motocross (using about 12" of travel), I found I actually got a plusher ride with a stiffer spring (front forks, and very little preload on the springs), that still resisted big bumps with less compression dampening, and more rebound dampening (assuming the dampers were set correctly with the stock springs). As for the preloaded travel of a dirt bike, you pretty much want your suspension to have eaten up about 33% of the total travel with you on the bike, no matter what your spring rates are, and that is adjusted by a preload ring that compresses the spring. But, if you add the dampening,--I bet the math work goes up exponentially---but it still has to work as well in the real world, and will need field testing to fix. Sophisticated suspension, (depending on the demands and severity of the application), seems to be one of those things that almost never comes off the drawing table very well. You should look at some of the front forks of MX bikes today. Nobody knows how to adjust them, there are so many knobs and air chambers. But one fork on Yamaha the kabaya (sp) SSS forks, that is over 10 yer old technology, and still uses a spring, romps them all in overall performance and probably every category. You post great stuff young man. I hope there are more like you.
With all things being equal, softer springs are better on bumpier surfaces (everyday roads) and harder springs are better for smoother surfaces (race track). But that is not entirely true, in race tracks you often have to ride the kerb for the best line and that requires both stiffness and softness at the same time. A good suspension has to be able to achieve both. My current car has suspension that is 3 times the spring rate of the stock suspension, but actually is more comfortable because of the damper design.
There is a very important point you missed, if not the most important. Roadcars are optimized for straight line rolling where load is equally dstributed to both sides of the car. Racecars are optimized for cornering where load is shifted to the outside wheels. So you need to calcualte spring stiffness and damping rate to that amount of load. when you corner with a soft spring, you lose alot of suspension travel right at the start because of body roll, thats because the springs are too soft for that scenario. with a stiffer spring you optimize for higher load, giving you less body roll and more suspension travel remains available mid corner. higher damping rates need to follow the higher spring rates in order to prevent unvanted body oscillating movement.
Don't forget that stiffer springs are more maniable on the steering input! It helps on fast direction changes like on a chicane, it is more responsive.
Another great explanation. And "...they're about to collide, which is unfortunate, but that's irrelevant..." always cracking me up with these deadpan matter-of-fact one-liners..
That was a good vid, I was one of those people who just randomly assumed stiff springs were better because of their use on race cars. Happy I know the difference between softer and stiffer springs and why they are used.
I'm surprised people actually still debated this. This was spot on to what I learned in school. stiffer suspension for street driven cars isn't always better. example: I had a 7gen galant that I threw springs (1in front/rear) and adjustable shocks on. Hard cornering was great, but the overall quality wasn't great, especially in the rain. I went through alot of trial and errors before I figured out that soft is safe.
Thanks for another great video. In the next one, can you explain how the dampers interact with the springs and the combination of the two affects handling? I'm thinking about whether to soften my dampers or not and would like to know what affects it might have.
Also there’s a huge difference between your dampeners and the spring rate which was what he seemed to be talking about ,and seems to of forgotten to mention what controls the spring rate..as shocks control the springs speed of return..changing your shock rate ISNT going to prevent it from slamming into a hole if it’s too heavy of a spring rate, but it will sure slow them down on the return.. if the car drops into the hole too fast.while making contact still..
great video as usual but you gotta also count/add that stiffer setup enables car to react faster to driver inputs, especially during direction changes (which is what racing is about)
This video is great and just touching the tip of the iceberg. If he made a video about all suspension differences it would be hours long not just a quick video to make you think a bit. Thanks man keep em coming!
The only time you want stiff springs is when you have to maintain a body height and even that is a huge trade off soft springs keeps heat out of the tires,less unsprung weight and more road compliance so larger contact patch means more mechanical grip and if you really want to get serious you will end up with bumpsprings on your shocks I would love to see a video on that
There're 3 basic things who affect each other: Range of spring, spring rate and the shock absorber. Particularly the shock absorbers have to be well matched. For example there are high- and low-speed compression/rebound-stages and also the viscosity of the damping oil matters.
Roll is not necessarily bad, if it's not excessive. Through suspension geometry (specifically an upper A arm that's shorter than the lower one), wheels can be made to favorably change camber camber angle during roll, for the outside wheel in a turn. It's called "camber gain". Within limits, roll can be beneficial and improve traction in a turn, if the suspension is designed for it. (Roll can raise the center of gravity slightly, but favorable changes in tire camber angle can have a larger effect.) Learned that from a really good engineer at Lotus.
Struts have negative camber gain (going more negative) but the rate at which it happens is usually not enough or too rapid for the tire. Struts also lose it REALLY quickly if your lower control arm goes beyond perpendicular to the strut's angle in front view. For a lot of cars this happens far too quickly. As you said though, roll/pitch/squat is beneficial to the extent that it doesn't hamper the car's responsiveness to inputs or the tire's ideal contact patch. Once a car rolls too far you start losing grip. That's why the answer to the question "how much spring rate is enough" depends heavily on the rest of the suspension and the form of motorsport you are doing.
Whiskey's Gaming Lounge Agree. It's why I said camber gain can be beneficial within limits. If it goes too far, it becomes counterproductive, exactly as you found. BTW I wasn't really referring to strut suspensions. Camber gain is best controlled with double A arms. Anyway, agree with your points. Thanks for sharing!
this is why its better fun to race standard cars around a field, they just keep going over bumps, the roads here in Ireland aren't really made for stiff ,lowered cars but there are many guys who mod their cars like this anyway.. usually known as felt spec
+TheRealDannyE The lower the offset number, the more the wheel will stick out. the higher the offset the wheel will be more in the wheel well and will be less aggressive. every car uses different offsets. So you have to choose wisely
springs....coils of metal...thats it..... I gotta say, the half course of physics I took, the most amazing thing to me was how refined the concept of a spring is. So simple and so useful. I just love this stuff. Great video! I wish I knew more. Guess I gotta go take a full physics course next....Thanks brother!
Very good explanation ! As you know & have to keep it simple for the layman . Shock absorbers , sway bars , bushings & tires etc. are also components of a suspension system & on the track , settings are softer in the wet vs. racing in dry conditions . Thanks for helping alot of people by posting this video !
wow, i learnt a lot about springs with this. Got me interested because i have been learning about bicycle rear suspension setup. Thanks a lot, I am gonna apply this new knowledge on my setup experiments!
***** Rally drivers also slide their cars because of a technique called "late apex turning" it just allows the driver to see more of turn before having to decide if he/she needs to turn a lot or little. The body roll sounds like a good point as well for why they slide though too
lowering its not the only way to reduce body roll. anti-sway bars at the front and rear, tuned for your car, will reduce body roll maintaining the under/oversteer balance. a lot of cars of today have soft dampers with stiff sway bars.
Jason, first off, a big fan thank you for making these videos for all of us to better understand the engineering behind cars and suspensions, they have been a big help for me in understanding what parts I might invest into my ride. I wanted to ask a clarifying question about the video, which is in reference to the drop that the wheel would have into the hypothetical pothole you discussed in this video. I understand what you were trying to say in the aspect of the importance of keeping all 4 tires on the ground as much as possible and with as much force as possible as this is the point of a suspension. However, what I am struggling with is understanding how the stiffer spring, that only compresses 10mm, would have a harder time hitting the ground compared to the softer spring that compresses 80mm. I struggle with envisioning this as being something that follows other aspects of physics, such as the overall weight of the car, and the speed as to which the wheel hits the bottom of the hypothetical pothole. If the stiffer spring only compresses 10mm and the pothole is deeper than 10mm then that would leave the assumption that the spring does not decompress further than 10mm, which when a car is lifted there is full droop in all 4 wheels, which is in response to the shocks and springs being fully extended and not being under pressure. For what you were saying in the video that the stiffer springs would not either reach the bottom of the pothole in the time that the softer ones would reach would also be assuming that the shocks are not factored into this statement because if what you were saying was the case then a car’s wheel would never experience full droop and would return to the base ride height + the decompression of the spring (10mm). I am confused because the speed as to when that wheel would hit the bottom of the pothole would also be dependent on the speed of the car moving forward + the speed of gravity as the car is being pulled down to the bottom of the pothole. It would sort of question also the speed difference between the spring decompressing and the speed of gravity (both forces would be happening simultaneously, the car falling and the spring decompressing). It also brings into question the force that would be impacted on the fall as well and looking at the spring rate to determine if the car’s force from the fall and momentum would cause the spring to compress more, thus potentially leading to bottoming out. As I see it, and I could be wrong, we have 3 forces in this hypothetical situation (the shocks, springs and gravity) and in “forces” I mean all things that would cause the wheel of the car to move downward in the event of driving over a pothole. All 3 would need to be taken into consideration when discussing the cons to stiffer springs, correct?
I usually enjoy your videos but this one has some bad logic. This is a very very special case, which almost never occurs. That is hitting a bump larger than your suspension droop. I've had cars on 12kg and 10kg springs. Even an FC RX7 with Mcpherson front suspension of almost 1:1 moment arm with 12kg springs would have nearly an inch of droop. Don't know about you but if there's a road with that crazy of a drop, I'm not driving on it! So following that special case you're discounting all the other benefits of stiff springs and claiming that softer springs are better for the street?
TheXdmgx7 The logic is sound. Softer springs will allow for more compliance with the road (even if the examples are exaggerated to keep the math simple and explain a point). This doesn't mean soft is "best" for the street, it's simply factual that in non-perfect conditions it will do a better job of maintaining contact with the ground. Design for what road conditions you intend to drive on.
TheXdmgx7 It becomes a problem when you consider the force on the body creating an upward acceleration from stiff springs. The back side of a 10mm bump can cause an aftermarket suspension to lose contact with the ground because the body continues it's velocity upward which drags the wheels up with it an reduces the load on the springs, which removes droop velocity. Using an aftermarket ride height and spring perch separated adjustment coilover you can easily tune the suspension to be harsh either on the front side or back side of bumps using the preload adjustment on the lower spring perch. If you have conventional single collar adjustable coilovers this won't work because you cannot preload. For instance, i can set up my coilovers to have zero preload and thus maximum shock compression at static height, which will make it more likely for the shock to contact the bump stops, drastically increasing effective spring rate over sufficiently sized bumps and causing compression to be uncomfortable. In reverse, I can preload the spring to the point of zero shock compression at static height and as such giving the shock minimum droop travel, making the front side impact of bumps very gooshy but the back side of bumps like falling off a cliff. So it depends on the ratio of shock length and spring rate to determine the actual road-contacty-ness of a coilover.
Engineering Explained I agree that in non-ideal(horrible) conditions softer springs will do a better job maintaining traction but you did not claim that softer springs are better for non-ideal conditions. You claimed softer springs are better because the harder spring will run out of droop if you jump a huge curb and you will lose contact. In the real world it is VERY hard to lose contact due to inadequate suspension droop. (I'd be dead 10 times over if that wasn't the case)
TheXdmgx7 your assertions about the difficulty of losing contact depend entirely on the properties of the shock and spring combination. My coilovers can and do regularly lose contact with the ground. Engineering's extreme examples lay the groundwork for how relative wheel and chassis velocities work together. He is correct. You're just having trouble working between the extremes. In his example, wheel forces of 2g, 4g, 6g etc between the two extremes of 1g and 10g are possible. Those forces relate to how quickly the wheel follows the back side of every bump. The closer to 1g the more often the car will lose contact with the road. This can be due to spring rate, damper settings (over-damping on rebound for instance, lowering wheel velocity on extension) and of course limited droop travel (which is the problem with my coilovers).
Gregory Evans I completely agree, yet this is not enough of a reason for the claim "softer springs are better for the street." My problem is not with the overly simplified math but with stretching it and using it as a proof for a much more broad claim. An example would be the moose test(Real world, right?)... How do you think a softly sprung car will do? It'll be less responsive due to the delayed weight transfer. See my point?
Excellent video. Although this is a real common-sense situation, a lot of people need to actually have it explained to them before they accept what they probably already knew. I don't understand all the mathematics here because I'm not a highly educated engineer, such as yourself, but you still manage to get your point across in an easy-to-understand manner. I want to say, that, although I am occasionally critical and don't always agree with what you say, I respect you and appreciate what you do here. We are close to the same age and remember a time when we didn't have the internet to answer all of our questions, and as much as I use it, I think it a little sad that humanity can't function without it anymore. But in this internet age, it's great that you dedicate so much of your time and knowledge to educating and helping others. Granted, you get paid for this, but you are living a dream, doing what you love, and you are a good person.
Thanks Ted! It's fine to not always agree with what I say, I make mistakes like everyone else! (Though I do try my best to correct them or point out my flaws when applicable). Glad to hear you enjoy the content, truly is the dream!
One thing he didn't address is that softer springs will allow the unsprung weight of the wheel to induce further suspension compression which can cause the tire to lose contact with the road for a longer period of time as it goes through the compression and rebound cycle. A badly washboarded road is a good example. If your soft springs allow the wheel a greater range of motion and a slower rebound, you will have less braking and turning traction with that wheel. If you hit a series of consecutive bumps the tire can bounce up and down on the road like a basketball. No tire has grip when it is in the air. You can compensate with stiffer shocks, but the shock and springs should be changed simultaneously or either can wear out prematurely. This is why it's a bad idea to add lower (shorter) springs while keeping the same shocks. They must have similar driving and handling characteristics and capabilities.
+Chris Ashcroft This is not correct. On a washboarded road the tire will maintain contact much more with a softer spring than with a stiffer spring, which will bounce the whole car. The reason this is true is demonstrated mathematically in the video, as the force pressing down on the spring will remain greater for whatever amount of travel there is in the spring. Think about a car with no suspension (aka, infinitely stiff springs). In this case, as you hit any bump, the entire car is forced up (and the tire loses contact). If the spring is super soft, the suspension travel will absorb the bump, and the tire will maintain contact with the road.
+Engineering Explained For a very stiff spring, yes, but what about a very soft spring? Now the spring is under control of the dampening (compression and rebound dampening), to help the tire follow the road. But, for a hypothetical example, if the spring rate is soft (or not hard enough to rebound quickly), over stutter bumps, the shock could actually "pack" up into it's travel, because the next bump and next bump and the next bump compressed the shock more, and more, and more, until the spring rate is in a stiffer range of motion or the suspension bottoms out. When that happens, it could act a lot like a overly stiff spring, forcing the chassis upwards. Selecting the correct spring rate for your application is probably more important than getting the dampening dialed in, but they have to work together, and it is usually futile to try to tinker with dampening if you have the wrong spring rate. I learned something during the dirt bike suspension evolution from about 3" of travel to about 12" of travel. It was not always the longer travel that made a suspension perform better, but how well the spring and dampening handle the travel you have.
+Chris Ashcroft not only am I an engineer but I drive washboarded unsealed roads every day. I have two identical cars (GC Mazda 626s). One is turbocharged and my toy on the track with correspondingly stiff suspension. It is a nightmare to drive on these roads. My carburetted daily driver has very soft suspension with a high spring rate and glides over these surface imperfections with ease. When cornering on these surfaces it is much more stable than the track designed one.
the rx-8 has a much softer suspension then the fd 7 for exactly that reason. it's almost unbelievable how well it mantains grip. damn fast in the real world, but not so much on a race track. that's one of the main reasons why i didn't buy an s2000. there also is the benefit of a smoother ride.
WRC cars have softer springs on tricky gravel tracks ans stiff spring on tarmac mostly. i agree with this guy. there's a lot of accidents with cats super 7 and lotus elise on mountain tracks due to the very stiff suspension configuration, its so stiff and short that the wheel cant fill the whole gap during a depression. result, lack of traction. mountain roads work better with medium spring rates, gravel with soft and corsa with stiff. it all depends of the amplitude of the irregularities. short amplitude, stiff, long amplitude soft.
I used to race superbikes and the suspension settings always had me on the fly, it depends on temperature and surface conditions you will use, for normal street use you can set a medium setting it will get the best of both sides from soft to hard, it is quite tricky to find the right setting at the beginning, but you will get use to it.
+Adnan Rahman I believe spring rate is about the force necessary to generate each 1mm of compression in the spring. so, the higher the spring rate, the stiffer the spring is.
Adnan Rahman haha i get what you mean. i think what throws people off is that the word "rate" is often used by normal people to describe some sort of speed or change in distance over time. here, it's really more about the spring's compression, so not much to do with time at all. glad it helped you!
+GunFun ZS Used those on an old caprice. Car was smooth sailing, but when it came time to load up, and you can load those things, didn't have to worry about sagging or bottoming out on a big bump.
Ok you helped us scratch the surface of understanding basic suspension physics. I think it would be great to talk about suspension setup on race cars both on road and off road that would be a very helpful video
Wonderful presentation! Always thought shocks were mostly for a comfortable ride (as in a Cadillac) but finding out it's really about keeping tires on the ground is new to me but makes all the sense in the world.
Roll is grip, if you can control it. Can't remember where I heard that the first time, but it's catchy and quickly explains the effects of spring rate.
EE, I think you are under-emphasizing the impact roll, dive and squat have on dynamic weight distribution. While softer suspension indeed maximizes grip (everything else being equal), the same soft suspension also results in a huge body roll, which, while turning, results in alot more weight being transferred from the inside wheels to the outside wheel. This causes the overall coefficient of friction to drop, resulting in LESS mechanical grip on smooth surfaces. Another advantage of the stiff suspension, that I believe is important to mention, reducing roll dive and squat allows the driver to control the vehicle more precisely, while going through a turn. It becomes even more important during transitions. (it takes less time for the vehicle to lean into the turn and to "take a set" when the suspension is stiff)
+drklop You're right, and I think it's disingenuous to say that the "only" purpose of suspension is to keep the tires contacting the ground. However, I think the lesson to take away from this is that a street car can suffer from having too stiff of suspension. I think my car is an example of this. The first owner put some very stiff suspension on it and it goes around smooth corners like a go-kart. When you turn the steering wheel, there is no perceptible lag whatsoever. However, I've hit some bumpy patches of road that made it really difficult to control. It would be a great setup on the track, but on these bumpy Dallas streets, I think softer suspension (softer than it currently is) would have been the way to go.
+drklop This is actually a very non-trivial matter, and there's no such answer as "softer/harder is grippier". As a simple example and counter-example, stiffer compression dampening can actually increase grip, as it makes the tire deform more around small bumps in the road increasing the surface contact. But too much compression dampening, and the tire begins to bounce up from those bumps. OTOH, one can reduce the rebound dampening to make the tire respond better to small pits in the road or bounces after bumps. But too much reduction, and the suspension begins oscillating. Little oscillation can be ok in a race car (although quite uncomfortable in a passenger car). But too much oscillation, and the tire begins once again bounce up from the road. The spring rates, dampers, and tires (+ sway bars, camber, caster, toe-in, and rest of the suspension&body geometry etc) must always be considered as a whole, and in the end, choosing the values is an optimization problem between comfort, grip, and driving "feel" over various surfaces. The more prestigious car manufacturers actually put a ton of effort in this area. And then ignorant tuners ruin their cars with some "cool" low-profile oversize tires, which make the ride uncomfortable and less grippy - even in the track, regardless what people in general believe. But I guess that as a general over-simplification, one can say that a softer setup is more grippier than the stiffer. But this applies only in the relatively small window around the sweet spot before other factors start to speak for the stiffer setup.
Body roll does not substantically contibute to overall weight transfer. There are very minor effects from CG migration, but that's it. Body roll is a symptom of weight transfer, not the cause. Body roll does hurt camber with non-solid axles and can cause earlier contact with bump stops, causing effective wheel rates to spike upwards.
I didn't get all of the verbal jargon a but I understood what you're saying as I feel them out on the road and track having stiff spring rates on both my cars.
Seems like you just talked about compression and left out preload and rebound. Your videos are great but to explain the real reasons behind race/street suspension in 6 minutes is impossible.
thanks for this video!!! very structured and well made! one minor thing i want to add, you said beginning at 3:45 that "the softer spring presses it [the wheel] down faster". In your example both springs press the wheels down equally fast, the stiffer spring is just less mm compressed in your case. your sentence implied (my opinion) that the softer spring itself is faster. you made it very clear that the rest of the travel distance to the ground is pulled by earth graviation, but this sentence alone seems a bit missleading for me. is this nitpicking? i hope you dont get mad over me! i really like your videos, please continue!! ;) cheers!
Phil Langer What I'm implying is that the wheel with a soft spring with more travel will contact the ground faster than the stiff spring with less travel. Less travel is a result of the stiffness of the spring, so they've very much intertwined.
Engineering Explained in your example yes the softer tyre with more travel would act faster but if the bump was smaller, like a race track bump of 10mm or less then the stiffer spring would react quicker, which is why race cars have those short suspension travel stiff spring setups. Also a softer spring is more compliant, easier to put power down etc however slower to react to weight shift. Understand though there are so so many aspects you can't cover it in one video. Suspension and spring setups are a fine art..
BenjiMC1 I would agree with Jason in the softer spring get's to the ground faster, even in your 10mm example. What you are neglecting is the pre-load on the springs. Both springs are pre-loaded with 10,000N but if the stiff spring experiences a 1 mm dip in the road it now only has 9000N while the soft spring (all from his example) would have 9900N. Since a=F/m the soft spring has more force with the same mass thus higher acceleration towards the new surface in the road.
TassieLorenzo Also means he can enter a corner faster, go look up suspension dynamics and you will see what going with a soft front vs a hard front does. Also oversteer is better than understeer as it can be controlled with enough practice.
TassieLorenzo oversteer is better than understeer and like they are right, soft front gives you better grip on the front wheels so better conering speed
What if the driver is 70 kg or 130Kg :D if u have soft springs and the person is heavy... than you get hard springs I think it is personal what the driver like, Comfortable or sport drive
yes maybe when the car is 1500kg then u not can see it maybe, but when i see my friend from 100kg step in his lowering car 980kg.. i see the car go more down on his side
MMD While the vast majority of cars are nowhere near that small, a 60 kg difference is still only 6% of the car. The car's stock suspension is designed to work with that kind of load and does not require a stiffer suspension.
I would love to see some sponsored content from Ohlins suspension on this channel. They are supposedly some of the most beautifully and meticulously designed suspension in terms of the quality of engineering and RnD that goes in to them. Plus they make them for your S2000 so you could get a set and try it out for free probably. I am interested to know how much of a difference their Dual Flow Valve technology makes on the street
Very nice explanation why race cars have stiff suspension, but what about off road vehicles. They too have stiffer springs, and their track is by no means smooth. Thanks and keep up the good work!!
I would love to see a video on variable rate vs. fixed rate springs if you haven't done one already! I searched the channel and didn't see one! This was a VERY informative video, really enjoyed it! I'm so fascinated with suspension tuning!
Robby94LS Variable rate springs aren't complicated... They just ramp from one rate to another as they are compressed, due to the variation in spacing of the coils.
Robby94LS I would think variable rate springs are better suited on vehicles that have a wider variation of light and heavy load conditions. For instance, a bigger car such as an SUV or a pickup truck w/c could turn from very light loading conditions such as when only the driver is the occupant, to very heavy loading, as when it is fully loaded to max capacity, could mitigate the "cons" of using a single rate soft OR stiff springs. In other words, variable rate springs allow you the characteristics of a soft spring when a stiff spring is not needed, and likewise can provide stiff spring action when the load demands it. Variable vs single rate springs are not better than the other as far as traction goes, provided the spring rate at any given amount of suspension travel are well suited for the load they were tasked to handle. A more relevant aspect to consider is the suspension geometry such that tire angles are optimal for enhancing traction.
I love your videos! I'm going through the pre-engineering classes for math and physics right now and I can only hope to remember half the stuff you explain. lol
Really good video and good food for thought. The only thing I would add to this, is particular with regards to racecars as a rough rule of thumb the stiffer the suspension, both in spring and bar the more it will put temperature into the tyre. Consequently when you start running race rubber you always play a delicate balancing act between mechanical grip and ensuring the tyre is up to temp.
Ok, the thing is that stiff springs are supposed to be used on tracks, because they affect weight distribution and weight shift and also handling, stiffer springs allow more weight to be charged on them without the worry of them being squeezed to death so this allows them to handle drift better allowing you to go faster, on the other hand soft springs really shines in everything else because either on track (only of you are a grip guy) or a downhill/uphill scenario you have overall better grip as well as a smooth turn, but at contrary if you want to drift you will have to go slower to avoid hitting the wall and it's easier to spin out so, on a soft spring drive grippy and safe, please correct me if i'm wrong, always looking forward to improve :)
"We've got two cars driving. They're about to collide which is unfortunate, but that's irrelevant." LOL
Watching the video again... still interesting 😂
LMAO.. . Was reading this comment as he said it.
Lol, correct! Hahahaha
Very factual as always..
Wait, that's Mr. Vortex radar
There both more factors involved, and more reasons for stiffer suspension. A major factor not discussed are the shocks. In the example above, the rate of wheel movement towards the ground (for the dip) did not factor in the shocks (rebound), nor did the bump example for the stiff spring. It is complicated.
Beyond that, stiffer springs help prevent body roll/lean and help keep the tire flat to the ground. Soft springs allow the body to roll, which changes the effective camber of the tire. If you compensate by adding static negative camber, this sacrifices straight line braking... stiffer allows for less static camber. And, stiffer means generally less tire wear (which is a major factor in racing, either for cost or for stint length.)
Finally, stiffer also is important for transitions from left turn to right (and vice-versa). Soft cars allow the body to roll from one side to the other and for that to be a large and slow transition. Stiff springs prevent the roll in the first place and switch to the other side faster. Stiffer tends to stabilize more quickly after sudden transitions.
So, its quite complicated. There is no best. Generally, for smooth tracks, stiffer is better. Generally, for bumpy tracks, softer is better. (Those comments are to be taken relatively to each other.)
Last but not least, driver preference/confidence vary a lot with how the car feels - some like stiffer/firmer (springs and shocks) and some like softer. So while the engineer may say one way or the other is technically or theoretically better, the driver may feel (and perform) better with a different setup.
Thanks for considering a complicated and interesting topic.
Summed up perfectly.
agree
What about Citroen DS cars? They drive as if they are floating over the road and yet they turn as if they have stiff suspension! How do they do it?
Good comment
Learned a lot between the video + this rebuttal. Thanks for the concise write-up!
"We have two cars driving. They're about to collide which is unfortunate..." This cracked me up. Probably because i am quite tired, but still, i thought it was funny that he found that worth mentioning. lol
Kaelin the Sergal Dragon Made me laugh indefinitely
"They're about to collide, which is unfortunate, but it's irrelevant" LOL
irrelevant xD
was staring at his collar the whole time
lmfaooooooooooooooo
+Wake Boarder replay*
here for this comment. It bugged me more than it should
lol
I laughed so hard at this xD
so basically, softer springs are better for bumpy roads, and harder springs are better for smooth roads
+Khazar01 with the one caveat that you can't go too soft for bumpy roads or your suspension will bottom out and hit the bump stops. which is way worse than having suspension that's a bit too hard.
Jethro Rose
agreed :)
+Khazar01 Somewhat, but really not that simple. Bumpy is relative to speed. A road may seem very smooth at 30 mph, but the small hills become very meaningful at 150 mph. It may look smooth but if you're going fast enough it will make the suspension work more, but of course there are other factors you need to consider about speed (as mentioned at the end of the video).
Khazar01 we didnt need any research to know this. But thanks i geenering xplained
I'm so confused with what kind of suspension to get in my car for Salt Spring Island. My wrx just started acting a bit like a marshmallow with a turbo strapped to it. Really awful B roads lots of roots ruts compression dips crests off cambered turns , pot holes etc. Rally suspension makes sense, except that I have road tires so that cancels that out. need to maintain grip when blasting around corners that want to knock you into a ditch, off a cliff or into a swamp.
he really really really likes to explain stuff
mark welsh explain why turtles make shitty pets
mark One if I was that smart I’d liked to explain stuff too
Let's hope so, because many of us really, really, really like listening to his breakdowns.
Thanks to you, I finally know what im doing when im tuning my cars in Forza 4 Horizon. Cheers mate!
Sometimes forza horizon 4's tuning dosen't make sense...
Don't put the suspension all the way up the stiff the car will understeer...
@@D7A1sounds like tires aren't up to the job.
I seriously appreciate someone who can breakdown a subject and explain it clearly thanks @engineeringexplained
Did you say "clearly"??
When they say "it's not rocket science"
Yeah... You understand.
I've always loved Colin Chapman's philosophy in car suspension design. Softer springs with long suspension travel always make for a better ride and better grip on rough roads. The main reason why mass production cars are given stiffer springs is because people have the tendency to rely on their perception that cars that roll are more likely to lose grip on a fast turn.
Cars that roll don’t handle as well, it’s a simple fact..also we don’t drive at freeway speeds in cars off road, he seems to forget suspension settings are able the road surface your driving on,which dictates the suspension settings which work best..off road a softer longer setting is best , on a road course it’s a different beast, and even then having a adjustable setup is best
Soft if you can handle the roll, since a soft suspension means grip. I've noticed that in some cars, just upgrading anti-roll bars and adding sticky tires improves the handling a much greater amount than when a lowered and stiffer suspension was added.
Unbearable Pain I disagree. Some people say the primary roll stiffness should come from the springs, not the sway bars. The sway bars reduce the independence of the suspension.
TassieLorenzo True, but in big V8 muscle cars the suspension isn't independent anyways.
TassieLorenzo totally untrue... wheel indepenence ist not nessesarily a good thing. the myth that stiff suspension and hard dampers are a good thing comes from formula 1. in formula 1 you want the car to have the same attitude to the road at all times to maximize downforce. "mechanical grip" is irrelevant in F1. but since a roadcar has no downforce soft suspension will be better. thats also the reason why for example ralleycars have really soft suspension compared to for example f1 cars even when the are driving a tarmac ralley.
MrBusunglueck "but since a roadcar has no downforce soft suspension will be better. " Then why do road-based race cars with no downforce have stiff suspension? ;)... I agree there is such a thing as too stiff, but driving some road car on a track day with Hoosiers and using stock comfort-tuned suspension will give a terrifying wallowy feeling and feeling of lack of control. There is a REASON after all why PROPER sporty cars like Renault Megane RS, Civic Type R, Lancer Evolution, indeed Ferrari F430, etc all come with relatively stiff suspension.... surely? ;)
TassieLorenzo
the thing is... racecars with no downforce dont have stiff suspension. the reason why all sportscars are stiff is cause thats what people want. the nurburgring laptime off the current 911 turbo s for example was set with the dampers in comfort mode. the nurburgring is a bumpy track, but still that says a lot for me.
2 more reasons why stiff springs work well on the track:
1. To give a driver better feedback with regard to surface changes or communicate tire compliance with the road. So if you hit a spot of gravel vs ice you can feel the changes.
2. Also with higher speeds on a track, impacts from road surface changes or even suspension movement due to braking or cornering causes more travel and uses suspension compliance forcing the shock to operate outside of it's optimum stroke. So stiffer suspension is needed in order for the components to handle higher speeds. Granted your tires still have to be good enough to generate the traction needed to allow for it's proper operation or you can loose more traction because of the loss of compliance.
If this dude built an entire car himself it would pull 4 lateral Gs and have a top speed of ∞
+Rough Muff No I don't think so, he would just understand why it wasn't that fast!! LOL.
Wet Towelette god damn.. this comment actually made me laugh out loud. Laughed more than I should and I dont even know why.
if he entered a race series he'd win, with no team.
If he wanted to bottom up design a car, I would help fund the dude. Guy should start a kickstarter collaborative with other car guys and design and build an affordable sports car that can be mass produced.
Why? He's just doing the same kind of engineering that's made at the factory. The output in that case would be a really nice, well engineered premium car, nothing out of this world.
Every time I watch your videos like this one, you just make me want to keep my car stock, and just learn how to drive what I have better. So thanks for saving me money lol.
Stock is general purpose needed, except you're a special driver 😁.
Top 5 best car channel on RUclips, hands down. The content value is amazing compared to most car channels.
how did i get here from gordon ramsays kitchen nightmares?
No idea, but I can start yelling loudly if it will make you feel more comfortable! :)
Skip M what are you even talking about lol?
Brandon Inu is the slight accent
What the F*** is this?? you call this a suspension??...DO IT AGAIN and this time make it STIFF
They have a passion for what they do
I am a bit confused. If we are just looking at spring rate, why aren't we looking at a spring that has enough travel to reach the 20mm? In that case the stiff spring would win, the only reason it loses is because it runs out of travel and gravity has to do the rest as you mentioned. I guess the video is not about preloading the spring and the only source of compression is vehicle weight.
If it was preloaded (as almost all passenger cars are, and why spring removal has to be done carefully even when the wheels are lifted off the ground), then the stiff spring should have ~10X faster ground contact in the dip. Your point is very valid on the bump force though.
davetek490 The amount the spring compresses is based on the weight on it. A stiffer spring will compress less, and thus have less travel.
10x faster ground contact? Nope, the math says otherwise (even in the portion where there is still travel remaining).
Engineering Explained
For the sake of being devils advocate I'm assuming a preload to allow stiff spring to travel 20mm. The stiffer spring has higher F/mm.... if F=ma, then if both springs are allowed to travel the full 20mm, at every mm of travel, the stiffer spring has more force. if a=F/m and m is constant, a is linearly higher with respect to F.
I must be missing something.
davetek490 The thing you're missing is that as the spring releases (look at the graph I drew) the amount of force it presses decreases (rapidly with a stiff spring, slowly with a soft spring). The maximum force both springs press is the same, but the soft spring will press with a greater force for longer (it does more work).
Engineering Explained
Ok, and that's only true in the case where the only force used to preload the spring is the 1000kg car. I get you, I think we're just using different initial conditions. Thanks for the explanation.
davetek490 a soft spring will make the car bouncy when the mass of the car is moving, like when you go over a crest. to stop this you ned a shockobsorber to steady out the pressure on tyres to keap traction. does a soft spring not need a harder obsorber with gives a harder spring some advatage when it comes to travel? great explanation on springs, very intresting
you should've just yelled "soft!" and then stared at the camera for 4 minutes.
+Nicholas Wilson Science and engineering are about the "whys", not just the "whats". In other words they're about understanding, not just knowing.
4 those of u who didn't fully understand. What he has explained is the perfect formula to base a suspension set up "coilovers". Thanks to this man and his video I understand completely on how to set up my car the way I want it. There are an infinite amount of spring rate set ups. What it comes down too is your own style of driving to formulate a functional set up for both street and track "AutoX". I'm headed in that direction. I want the best of both worlds because math makes that possible. Thank you for your injenuity.
When you add the effects of compression and rebound dampening (oil damper), this gets much more complicated than just a spring with no damper. In fact, a spring alone does a terrible job of keeping the wheel on the ground.
Playing with dirt bike suspension in the good old days of Motocross (using about 12" of travel), I found I actually got a plusher ride with a stiffer spring (front forks, and very little preload on the springs), that still resisted big bumps with less compression dampening, and more rebound dampening (assuming the dampers were set correctly with the stock springs).
As for the preloaded travel of a dirt bike, you pretty much want your suspension to have eaten up about 33% of the total travel with you on the bike, no matter what your spring rates are, and that is adjusted by a preload ring that compresses the spring.
But, if you add the dampening,--I bet the math work goes up exponentially---but it still has to work as well in the real world, and will need field testing to fix.
Sophisticated suspension, (depending on the demands and severity of the application), seems to be one of those things that almost never comes off the drawing table very well.
You should look at some of the front forks of MX bikes today. Nobody knows how to adjust them, there are so many knobs and air chambers. But one fork on Yamaha the kabaya (sp) SSS forks, that is over 10 yer old technology, and still uses a spring, romps them all in overall performance and probably every category.
You post great stuff young man. I hope there are more like you.
You really know what you are talking about and your not boring. I appreciate the helpful information.
With all things being equal, softer springs are better on bumpier surfaces (everyday roads) and harder springs are better for smoother surfaces (race track). But that is not entirely true, in race tracks you often have to ride the kerb for the best line and that requires both stiffness and softness at the same time. A good suspension has to be able to achieve both. My current car has suspension that is 3 times the spring rate of the stock suspension, but actually is more comfortable because of the damper design.
There is a very important point you missed, if not the most important.
Roadcars are optimized for straight line rolling where load is equally dstributed to both sides of the car. Racecars are optimized for cornering where load is shifted to the outside wheels. So you need to calcualte spring stiffness and damping rate to that amount of load. when you corner with a soft spring, you lose alot of suspension travel right at the start because of body roll, thats because the springs are too soft for that scenario. with a stiffer spring you optimize for higher load, giving you less body roll and more suspension travel remains available mid corner. higher damping rates need to follow the higher spring rates in order to prevent unvanted body oscillating movement.
0:28 that made me laugh harder than it should have...
PotatoadZ 0:29
0:30
0:24
Don't forget that stiffer springs are more maniable on the steering input! It helps on fast direction changes like on a chicane, it is more responsive.
i’ve never gotten confused quicker than watching this video
Another great explanation. And "...they're about to collide, which is unfortunate, but that's irrelevant..." always cracking me up with these deadpan matter-of-fact one-liners..
You should do a video on air suspension
That was a good vid, I was one of those people who just randomly assumed stiff springs were better because of their use on race cars. Happy I know the difference between softer and stiffer springs and why they are used.
man, I love these videos.
I'm surprised people actually still debated this. This was spot on to what I learned in school. stiffer suspension for street driven cars isn't always better. example: I had a 7gen galant that I threw springs (1in front/rear) and adjustable shocks on. Hard cornering was great, but the overall quality wasn't great, especially in the rain. I went through alot of trial and errors before I figured out that soft is safe.
Thanks for another great video. In the next one, can you explain how the dampers interact with the springs and the combination of the two affects handling? I'm thinking about whether to soften my dampers or not and would like to know what affects it might have.
Yeah if your driving over pot holes and not on your typical race surface
Also there’s a huge difference between your dampeners and the spring rate which was what he seemed to be talking about ,and seems to of forgotten to mention what controls the spring rate..as shocks control the springs speed of return..changing your shock rate ISNT going to prevent it from slamming into a hole if it’s too heavy of a spring rate, but it will sure slow them down on the return.. if the car drops into the hole too fast.while making contact still..
This actually helps me a ton with my mountain bike, this makes suspension sag make a ton more sense.
great video as usual
but you gotta also count/add that stiffer setup enables car to react faster to driver inputs, especially during direction changes (which is what racing is about)
Not drag racing.
This video is great and just touching the tip of the iceberg. If he made a video about all suspension differences it would be hours long not just a quick video to make you think a bit. Thanks man keep em coming!
Zoinks, this guy's spooky smart, scoob...there's like, no way i can keep up.
i wish i had a ham sandwich to like, calm my nerves man...
Too many hash scoobie snacks
Playboysmurf1 straight off the tree in my house
Dammit. .. I read this like Shaggy in my head.
Pan tera LMAO
Pan tera 🤘🏽Pantera🤘🏽 kicks ass
Screw school, the only thing I need is your channel
sooo... whats better? soft or hard springs?
I think I have a video covering this... it depends. :) As soft as you can get, without compromising other factors too much.
exactly!!!!!!!!!!!!!!!!
street car go with soft , race car go with hard
provided you have smooth roads to drive the race car on
The only time you want stiff springs is when you have to maintain a body height and even that is a huge trade off soft springs keeps heat out of the tires,less unsprung weight and more road compliance so larger contact patch means more mechanical grip and if you really want to get serious you will end up with bumpsprings on your shocks I would love to see a video on that
There're 3 basic things who affect each other: Range of spring, spring rate and the shock absorber.
Particularly the shock absorbers have to be well matched. For example there are high- and low-speed compression/rebound-stages and also the viscosity of the damping oil matters.
Roll is not necessarily bad, if it's not excessive. Through suspension geometry (specifically an upper A arm that's shorter than the lower one), wheels can be made to favorably change camber camber angle during roll, for the outside wheel in a turn. It's called "camber gain". Within limits, roll can be beneficial and improve traction in a turn, if the suspension is designed for it. (Roll can raise the center of gravity slightly, but favorable changes in tire camber angle can have a larger effect.) Learned that from a really good engineer at Lotus.
+Loanword Eggcorn Presuming you have a wishbone suspension of course, which most cars do not.
Chris Ashcroft Yes, double A arm suspensions are less common than strut suspensions. But they're more common than they were in the past few decades.
Struts have negative camber gain (going more negative) but the rate at which it happens is usually not enough or too rapid for the tire. Struts also lose it REALLY quickly if your lower control arm goes beyond perpendicular to the strut's angle in front view. For a lot of cars this happens far too quickly.
As you said though, roll/pitch/squat is beneficial to the extent that it doesn't hamper the car's responsiveness to inputs or the tire's ideal contact patch. Once a car rolls too far you start losing grip.
That's why the answer to the question "how much spring rate is enough" depends heavily on the rest of the suspension and the form of motorsport you are doing.
Whiskey's Gaming Lounge Agree. It's why I said camber gain can be beneficial within limits. If it goes too far, it becomes counterproductive, exactly as you found. BTW I wasn't really referring to strut suspensions. Camber gain is best controlled with double A arms. Anyway, agree with your points. Thanks for sharing!
this is why its better fun to race standard cars around a field, they just keep going over bumps, the roads here in Ireland aren't really made for stiff ,lowered cars but there are many guys who mod their cars like this anyway.. usually known as felt spec
Do a video on rim offset
+Kurtis Snyder Agreed. I need to understand it better.
+TheRealDannyE The lower the offset number, the more the wheel will stick out. the higher the offset the wheel will be more in the wheel well and will be less aggressive. every car uses different offsets. So you have to choose wisely
I thought it was the other way around.
One of the best among best channel....
"They're about to collide...so that's unfortunate" hahaha😂😂
springs....coils of metal...thats it..... I gotta say, the half course of physics I took, the most amazing thing to me was how refined the concept of a spring is. So simple and so useful. I just love this stuff. Great video! I wish I knew more. Guess I gotta go take a full physics course next....Thanks brother!
Very good explanation ! As you know & have to keep it simple for the layman . Shock absorbers , sway bars , bushings & tires etc. are also components of a suspension system & on the track , settings are softer in the wet vs. racing in dry conditions . Thanks for helping alot of people by posting this video !
wow, i learnt a lot about springs with this. Got me interested because i have been learning about bicycle rear suspension setup. Thanks a lot, I am gonna apply this new knowledge on my setup experiments!
So what's going on with rally suspension? I know they have lots of travel but are they stiff or soft?
I guess they have a "pretty soft" but not too soft springs with very very good damping
soft suspension
GrahamBartle soft springs, hard shocks and long travel.
*****
Rally drivers also slide their cars because of a technique called "late apex turning" it just allows the driver to see more of turn before having to decide if he/she needs to turn a lot or little. The body roll sounds like a good point as well for why they slide though too
lowering its not the only way to reduce body roll. anti-sway bars at the front and rear, tuned for your car, will reduce body roll maintaining the under/oversteer balance. a lot of cars of today have soft dampers with stiff sway bars.
great video. i liked the thorough walkthrough of the physics and then the applications with race setup. please do more like that.
So basically E=mc2 times the Pythagorean Theorem, giving you the lowest common denominator of the Seventh layer of the OSI model.
Jason, first off, a big fan thank you for making these
videos for all of us to better understand the engineering behind cars and
suspensions, they have been a big help for me in understanding what parts I
might invest into my ride. I wanted to ask a clarifying question about the
video, which is in reference to the drop that the wheel would have into the
hypothetical pothole you discussed in this video. I understand what you were
trying to say in the aspect of the importance of keeping all 4 tires on the
ground as much as possible and with as much force as possible as this is the
point of a suspension. However, what I am struggling with is understanding how
the stiffer spring, that only compresses 10mm, would have a harder time hitting
the ground compared to the softer spring that compresses 80mm. I struggle with
envisioning this as being something that follows other aspects of physics, such
as the overall weight of the car, and the speed as to which the wheel hits the
bottom of the hypothetical pothole. If the stiffer spring only compresses 10mm
and the pothole is deeper than 10mm then that would leave the assumption that
the spring does not decompress further than 10mm, which when a car is lifted
there is full droop in all 4 wheels, which is in response to the shocks and
springs being fully extended and not being under pressure. For what you were
saying in the video that the stiffer springs would not either reach the bottom
of the pothole in the time that the softer ones would reach would also be
assuming that the shocks are not factored into this statement because if what
you were saying was the case then a car’s wheel would never experience full
droop and would return to the base ride height + the decompression of the
spring (10mm). I am confused because the speed as to when that wheel would hit
the bottom of the pothole would also be dependent on the speed of the car
moving forward + the speed of gravity as the car is being pulled down to the
bottom of the pothole. It would sort of question also the speed difference
between the spring decompressing and the speed of gravity (both forces would be
happening simultaneously, the car falling and the spring decompressing). It
also brings into question the force that would be impacted on the fall as well
and looking at the spring rate to determine if the car’s force from the fall
and momentum would cause the spring to compress more, thus potentially leading
to bottoming out. As I see it, and I could be wrong, we have 3 forces in this
hypothetical situation (the shocks, springs and gravity) and in “forces” I mean
all things that would cause the wheel of the car to move downward in the event
of driving over a pothole. All 3 would need to be taken into consideration when
discussing the cons to stiffer springs, correct?
Michael Capozzi is this a poem?
I usually enjoy your videos but this one has some bad logic. This is a very very special case, which almost never occurs. That is hitting a bump larger than your suspension droop. I've had cars on 12kg and 10kg springs. Even an FC RX7 with Mcpherson front suspension of almost 1:1 moment arm with 12kg springs would have nearly an inch of droop. Don't know about you but if there's a road with that crazy of a drop, I'm not driving on it!
So following that special case you're discounting all the other benefits of stiff springs and claiming that softer springs are better for the street?
TheXdmgx7 The logic is sound. Softer springs will allow for more compliance with the road (even if the examples are exaggerated to keep the math simple and explain a point). This doesn't mean soft is "best" for the street, it's simply factual that in non-perfect conditions it will do a better job of maintaining contact with the ground. Design for what road conditions you intend to drive on.
TheXdmgx7 It becomes a problem when you consider the force on the body creating an upward acceleration from stiff springs. The back side of a 10mm bump can cause an aftermarket suspension to lose contact with the ground because the body continues it's velocity upward which drags the wheels up with it an reduces the load on the springs, which removes droop velocity.
Using an aftermarket ride height and spring perch separated adjustment coilover you can easily tune the suspension to be harsh either on the front side or back side of bumps using the preload adjustment on the lower spring perch. If you have conventional single collar adjustable coilovers this won't work because you cannot preload. For instance, i can set up my coilovers to have zero preload and thus maximum shock compression at static height, which will make it more likely for the shock to contact the bump stops, drastically increasing effective spring rate over sufficiently sized bumps and causing compression to be uncomfortable. In reverse, I can preload the spring to the point of zero shock compression at static height and as such giving the shock minimum droop travel, making the front side impact of bumps very gooshy but the back side of bumps like falling off a cliff.
So it depends on the ratio of shock length and spring rate to determine the actual road-contacty-ness of a coilover.
Engineering Explained I agree that in non-ideal(horrible) conditions softer springs will do a better job maintaining traction but you did not claim that softer springs are better for non-ideal conditions. You claimed softer springs are better because the harder spring will run out of droop if you jump a huge curb and you will lose contact.
In the real world it is VERY hard to lose contact due to inadequate suspension droop. (I'd be dead 10 times over if that wasn't the case)
TheXdmgx7 your assertions about the difficulty of losing contact depend entirely on the properties of the shock and spring combination. My coilovers can and do regularly lose contact with the ground. Engineering's extreme examples lay the groundwork for how relative wheel and chassis velocities work together. He is correct. You're just having trouble working between the extremes. In his example, wheel forces of 2g, 4g, 6g etc between the two extremes of 1g and 10g are possible. Those forces relate to how quickly the wheel follows the back side of every bump. The closer to 1g the more often the car will lose contact with the road. This can be due to spring rate, damper settings (over-damping on rebound for instance, lowering wheel velocity on extension) and of course limited droop travel (which is the problem with my coilovers).
Gregory Evans I completely agree, yet this is not enough of a reason for the claim "softer springs are better for the street."
My problem is not with the overly simplified math but with stretching it and using it as a proof for a much more broad claim.
An example would be the moose test(Real world, right?)... How do you think a softly sprung car will do? It'll be less responsive due to the delayed weight transfer. See my point?
The fact these videos are free is mind blowing to me. Thanks for all the info you put out there!
I cannot go too stiff because my city is full of "depressions". LOL
Excellent video. Although this is a real common-sense situation, a lot of people need to actually have it explained to them before they accept what they probably already knew. I don't understand all the mathematics here because I'm not a highly educated engineer, such as yourself, but you still manage to get your point across in an easy-to-understand manner.
I want to say, that, although I am occasionally critical and don't always agree with what you say, I respect you and appreciate what you do here. We are close to the same age and remember a time when we didn't have the internet to answer all of our questions, and as much as I use it, I think it a little sad that humanity can't function without it anymore. But in this internet age, it's great that you dedicate so much of your time and knowledge to educating and helping others. Granted, you get paid for this, but you are living a dream, doing what you love, and you are a good person.
Thanks Ted! It's fine to not always agree with what I say, I make mistakes like everyone else! (Though I do try my best to correct them or point out my flaws when applicable). Glad to hear you enjoy the content, truly is the dream!
One thing he didn't address is that softer springs will allow the unsprung weight of the wheel to induce further suspension compression which can cause the tire to lose contact with the road for a longer period of time as it goes through the compression and rebound cycle. A badly washboarded road is a good example. If your soft springs allow the wheel a greater range of motion and a slower rebound, you will have less braking and turning traction with that wheel. If you hit a series of consecutive bumps the tire can bounce up and down on the road like a basketball. No tire has grip when it is in the air. You can compensate with stiffer shocks, but the shock and springs should be changed simultaneously or either can wear out prematurely. This is why it's a bad idea to add lower (shorter) springs while keeping the same shocks. They must have similar driving and handling characteristics and capabilities.
+Chris Ashcroft This is not correct. On a washboarded road the tire will maintain contact much more with a softer spring than with a stiffer spring, which will bounce the whole car. The reason this is true is demonstrated mathematically in the video, as the force pressing down on the spring will remain greater for whatever amount of travel there is in the spring. Think about a car with no suspension (aka, infinitely stiff springs). In this case, as you hit any bump, the entire car is forced up (and the tire loses contact). If the spring is super soft, the suspension travel will absorb the bump, and the tire will maintain contact with the road.
+Engineering Explained
For a very stiff spring, yes, but what about a very soft spring?
Now the spring is under control of the dampening (compression and rebound dampening), to help the tire follow the road. But, for a hypothetical example, if the spring rate is soft (or not hard enough to rebound quickly), over stutter bumps, the shock could actually "pack" up into it's travel, because the next bump and next bump and the next bump compressed the shock more, and more, and more, until the spring rate is in a stiffer range of motion or the suspension bottoms out. When that happens, it could act a lot like a overly stiff spring, forcing the chassis upwards.
Selecting the correct spring rate for your application is probably more important than getting the dampening dialed in, but they have to work together, and it is usually futile to try to tinker with dampening if you have the wrong spring rate.
I learned something during the dirt bike suspension evolution from about 3" of travel to about 12" of travel. It was not always the longer travel that made a suspension perform better, but how well the spring and dampening handle the travel you have.
+Chris Ashcroft not only am I an engineer but I drive washboarded unsealed roads every day. I have two identical cars (GC Mazda 626s). One is turbocharged and my toy on the track with correspondingly stiff suspension. It is a nightmare to drive on these roads. My carburetted daily driver has very soft suspension with a high spring rate and glides over these surface imperfections with ease. When cornering on these surfaces it is much more stable than the track designed one.
the rx-8 has a much softer suspension then the fd 7 for exactly that reason. it's almost unbelievable how well it mantains grip. damn fast in the real world, but not so much on a race track. that's one of the main reasons why i didn't buy an s2000.
there also is the benefit of a smoother ride.
WRC cars have softer springs on tricky gravel tracks ans stiff spring on tarmac mostly. i agree with this guy. there's a lot of accidents with cats super 7 and lotus elise on mountain tracks due to the very stiff suspension configuration, its so stiff and short that the wheel cant fill the whole gap during a depression. result, lack of traction. mountain roads work better with medium spring rates, gravel with soft and corsa with stiff. it all depends of the amplitude of the irregularities. short amplitude, stiff, long amplitude soft.
I used to race superbikes and the suspension settings always had me on the fly, it depends on temperature and surface conditions you will use, for normal street use you can set a medium setting it will get the best of both sides from soft to hard, it is quite tricky to find the right setting at the beginning, but you will get use to it.
Is that spring rate or spring stiffness? or are they both the same thing?
+Adnan Rahman I use them interchangeably. Ultimately you're measuring force over distance (how much force is required to compress the spring 1 mm).
+Adnan Rahman I believe spring rate is about the force necessary to generate each 1mm of compression in the spring. so, the higher the spring rate, the stiffer the spring is.
Thanks for the response guys. I was just a little confused because I always took rate as something per unit of time
Adnan Rahman haha i get what you mean. i think what throws people off is that the word "rate" is often used by normal people to describe some sort of speed or change in distance over time.
here, it's really more about the spring's compression, so not much to do with time at all. glad it helped you!
Your videos keep getting better! Keep up the good work
Of course the best question is "why not both" --- variable rate springs.
+GunFun ZS because until recently variable rate damping didn't exist.
That's true for a lot of things. It's still the right question.
+GunFun ZS Hydraulics suspension, i think is the solution
+GunFun ZS Used those on an old caprice. Car was smooth sailing, but when it came time to load up, and you can load those things, didn't have to worry about sagging or bottoming out on a big bump.
Ok you helped us scratch the surface of understanding basic suspension physics. I think it would be great to talk about suspension setup on race cars both on road and off road that would be a very helpful video
this is "suspension for dummies 101". Pure basic knowledge. There is much, much more to say about suspension.
Wonderful presentation! Always thought shocks were mostly for a comfortable ride (as in a Cadillac) but finding out it's really about keeping tires on the ground is new to me but makes all the sense in the world.
I didn't have time to watch this video, but it shouldn't be left without a like.
Roll is grip, if you can control it. Can't remember where I heard that the first time, but it's catchy and quickly explains the effects of spring rate.
EE, I think you are under-emphasizing the impact roll, dive and squat have on dynamic weight distribution. While softer suspension indeed maximizes grip (everything else being equal), the same soft suspension also results in a huge body roll, which, while turning, results in alot more weight being transferred from the inside wheels to the outside wheel. This causes the overall coefficient of friction to drop, resulting in LESS mechanical grip on smooth surfaces.
Another advantage of the stiff suspension, that I believe is important to mention, reducing roll dive and squat allows the driver to control the vehicle more precisely, while going through a turn. It becomes even more important during transitions. (it takes less time for the vehicle to lean into the turn and to "take a set" when the suspension is stiff)
+drklop You're right, and I think it's disingenuous to say that the "only" purpose of suspension is to keep the tires contacting the ground. However, I think the lesson to take away from this is that a street car can suffer from having too stiff of suspension.
I think my car is an example of this. The first owner put some very stiff suspension on it and it goes around smooth corners like a go-kart. When you turn the steering wheel, there is no perceptible lag whatsoever. However, I've hit some bumpy patches of road that made it really difficult to control. It would be a great setup on the track, but on these bumpy Dallas streets, I think softer suspension (softer than it currently is) would have been the way to go.
+drklop This is actually a very non-trivial matter, and there's no such answer as "softer/harder is grippier". As a simple example and counter-example, stiffer compression dampening can actually increase grip, as it makes the tire deform more around small bumps in the road increasing the surface contact. But too much compression dampening, and the tire begins to bounce up from those bumps. OTOH, one can reduce the rebound dampening to make the tire respond better to small pits in the road or bounces after bumps. But too much reduction, and the suspension begins oscillating. Little oscillation can be ok in a race car (although quite uncomfortable in a passenger car). But too much oscillation, and the tire begins once again bounce up from the road.
The spring rates, dampers, and tires (+ sway bars, camber, caster, toe-in, and rest of the suspension&body geometry etc) must always be considered as a whole, and in the end, choosing the values is an optimization problem between comfort, grip, and driving "feel" over various surfaces. The more prestigious car manufacturers actually put a ton of effort in this area. And then ignorant tuners ruin their cars with some "cool" low-profile oversize tires, which make the ride uncomfortable and less grippy - even in the track, regardless what people in general believe.
But I guess that as a general over-simplification, one can say that a softer setup is more grippier than the stiffer. But this applies only in the relatively small window around the sweet spot before other factors start to speak for the stiffer setup.
true, the added weight on the outside will never equal the grip of four tires with weight.
Body roll does not substantically contibute to overall weight transfer. There are very minor effects from CG migration, but that's it. Body roll is a symptom of weight transfer, not the cause.
Body roll does hurt camber with non-solid axles and can cause earlier contact with bump stops, causing effective wheel rates to spike upwards.
I didn't get all of the verbal jargon a but I understood what you're saying as I feel them out on the road and track having stiff spring rates on both my cars.
Seems like you just talked about compression and left out preload and rebound. Your videos are great but to explain the real reasons behind race/street suspension in 6 minutes is impossible.
Dani2wheels That's why I have more than one video on suspensions. :) Not trying to cover everything in one video, just spring rates for this one.
Engineering Explained i think the title should have spring in it instead of the blanket of suspension
AMGV Media Done!
Wow! The physics is reeel! I figured that's what stiff suspension meant, but now I have a better understanding of it. Thanks!
My head still feels the "race suspension" from s friends car. I dont know why anyone wants a race suspension on a daily car
Sharp ricers!!!😂
Posers.
Because sacrificing performance for comfort is for pussies.
thanks for this video!!! very structured and well made!
one minor thing i want to add, you said beginning at 3:45 that "the softer spring presses it [the wheel] down faster". In your example both springs press the wheels down equally fast, the stiffer spring is just less mm compressed in your case. your sentence implied (my opinion) that the softer spring itself is faster. you made it very clear that the rest of the travel distance to the ground is pulled by earth graviation, but this sentence alone seems a bit missleading for me.
is this nitpicking? i hope you dont get mad over me!
i really like your videos, please continue!! ;)
cheers!
Phil Langer What I'm implying is that the wheel with a soft spring with more travel will contact the ground faster than the stiff spring with less travel. Less travel is a result of the stiffness of the spring, so they've very much intertwined.
Engineering Explained in your example yes the softer tyre with more travel would act faster but if the bump was smaller, like a race track bump of 10mm or less then the stiffer spring would react quicker, which is why race cars have those short suspension travel stiff spring setups. Also a softer spring is more compliant, easier to put power down etc however slower to react to weight shift. Understand though there are so so many aspects you can't cover it in one video. Suspension and spring setups are a fine art..
BenjiMC1 I would agree with Jason in the softer spring get's to the ground faster, even in your 10mm example. What you are neglecting is the pre-load on the springs. Both springs are pre-loaded with 10,000N but if the stiff spring experiences a 1 mm dip in the road it now only has 9000N while the soft spring (all from his example) would have 9900N. Since a=F/m the soft spring has more force with the same mass thus higher acceleration towards the new surface in the road.
This could sound bad but i prefer soft on front and stiff on the rear XD lol
***** Hello oversteer!!
TassieLorenzo Also means he can enter a corner faster, go look up suspension dynamics and you will see what going with a soft front vs a hard front does. Also oversteer is better than understeer as it can be controlled with enough practice.
TassieLorenzo Dat weight transfer though, better for braking and cornering, especially if he has an FWD car.
TassieLorenzo oversteer is better than understeer and like they are right, soft front gives you better grip on the front wheels so better conering speed
Your vids are the best man. Ur extremely talented.
Progressively wound springs. Best of both worlds.
+Jack Allen nope
Another excellent video. Keep up the great work.
Ah ha, so that's what Einstein was talking about ?!?
I really enjoyed this video as I do the rest of his videos
What if the driver is 70 kg or 130Kg :D if u have soft springs and the person is heavy... than you get hard springs
I think it is personal what the driver like, Comfortable or sport drive
Driver weight generally has no impact on how the suspension performs.... You're talking a 60 kg difference in a 1500kg car.
yes maybe when the car is 1500kg then u not can see it maybe, but when i see my friend from 100kg step in his lowering car 980kg.. i see the car go more down on his side
MMD While the vast majority of cars are nowhere near that small, a 60 kg difference is still only 6% of the car. The car's stock suspension is designed to work with that kind of load and does not require a stiffer suspension.
and also when u put a big subwoofer in the trunk the car go down, so not very usefull information in this video ;)
MMD For example, in a 900 kg Mitsubishi Mirage, the suspension is designed to support an additional 400 kg in passengers and cargo.
I thoroughly enjoy your videos. Thank you so much for taking the time to make them
this is almost as true as 9/11
I would love to see some sponsored content from Ohlins suspension on this channel. They are supposedly some of the most beautifully and meticulously designed suspension in terms of the quality of engineering and RnD that goes in to them. Plus they make them for your S2000 so you could get a set and try it out for free probably. I am interested to know how much of a difference their Dual Flow Valve technology makes on the street
I think stiff is always better............
You think wrong, next time look video before coment.
thank you very much.. I was looking for this path to support it.. regards from Mexico.
crazy video bro u r the best on youtube
Nice job with these videos. I am an Engineer by training and still learn a ton from these short videos. Thank You for the good information
Very nice explanation why race cars have stiff suspension, but what about off road vehicles. They too have stiffer springs, and their track is by no means smooth. Thanks and keep up the good work!!
My brain hurts, but a great explanation Jason. For some reason I'm craving Fig Newtons now. ;)
I love how you explain how stuff works.
I would love to see a video on variable rate vs. fixed rate springs if you haven't done one already! I searched the channel and didn't see one!
This was a VERY informative video, really enjoyed it! I'm so fascinated with suspension tuning!
Robby94LS Variable rate springs aren't complicated... They just ramp from one rate to another as they are compressed, due to the variation in spacing of the coils.
I knew that much, but I really like how @EngineeringExplained goes very in depth, history, advantages and disadvantages!
Robby94LS I would think variable rate springs are better suited on vehicles that have a wider variation of light and heavy load conditions. For instance, a bigger car such as an SUV or a pickup truck w/c could turn from very light loading conditions such as when only the driver is the occupant, to very heavy loading, as when it is fully loaded to max capacity, could mitigate the "cons" of using a single rate soft OR stiff springs. In other words, variable rate springs allow you the characteristics of a soft spring when a stiff spring is not needed, and likewise can provide stiff spring action when the load demands it. Variable vs single rate springs are not better than the other as far as traction goes, provided the spring rate at any given amount of suspension travel are well suited for the load they were tasked to handle. A more relevant aspect to consider is the suspension geometry such that tire angles are optimal for enhancing traction.
Yes, thanks Marek Sumguy! It's been like 7 years since I've talked suspension so I'm a little rusty!
+Ro. .bby94LS
I enjoy your videos and your on point most of the time. Thank you for your uploads.
Never thought of it like that! Your whiteboard drawings are amazing by the way!
Love your vids Bro....Always spitting that good knowledge. love the math behind the outcome. We need more enthusiast like you.
Very informative as usual
Thanks, you do a great job reviewing cars and explaining technical subjects
You are the best my friend keep up the good work.
I thought I was watching mechanic stuff. This is an engineering class!
I love your videos! I'm going through the pre-engineering classes for math and physics right now and I can only hope to remember half the stuff you explain. lol
Really good video and good food for thought. The only thing I would add to this, is particular with regards to racecars as a rough rule of thumb the stiffer the suspension, both in spring and bar the more it will put temperature into the tyre. Consequently when you start running race rubber you always play a delicate balancing act between mechanical grip and ensuring the tyre is up to temp.
This guy knows his shit, usually know it alls love arguing about cars, but no one even attempts to challenge this guy.
Cornwall1888 I get it wrong from time to time! Try my best to research thoroughly before posting though.
i wonder what kind of suspension WRC rally cars are setup with, i would think maybe a in between setting?
Ok, the thing is that stiff springs are supposed to be used on tracks, because they affect weight distribution and weight shift and also handling, stiffer springs allow more weight to be charged on them without the worry of them being squeezed to death so this allows them to handle drift better allowing you to go faster, on the other hand soft springs really shines in everything else because either on track (only of you are a grip guy) or a downhill/uphill scenario you have overall better grip as well as a smooth turn, but at contrary if you want to drift you will have to go slower to avoid hitting the wall and it's easier to spin out so, on a soft spring drive grippy and safe, please correct me if i'm wrong, always looking forward to improve :)