Strut Tower Brace or Towel Bar? Engineering Explained
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- Опубликовано: 21 авг 2024
- Is this a strut tower brace or towel bar? I love the channel engineering explained, so here's my version regarding the common suspension brace.
Here is part 2 of this video where I road test the car with load cell forces - • Does a Porsche 911 Str...
Thanks for watching! Please click here to follow the 911 build progress in chronological order (oldest to newest)
• All Porsche 911 Restor...
This is a continuation video of my seam welded chassis torsional rigidity tests. This time I measure the effectiveness of the front strut tower brace bar for my Porsche 911. And a load cell is inserted into the strut bar to determine how much force the bar transfers from tower to tower.
Here's the link to an excellent Pelican thread about strut tower strength:
forums.pelicanp...
Similar load cell:
amzn.to/2RR138z
This video series filmed in my home workshop highlights the technical details of my classic car restoration (An aircooled Porsche 911). I’m starting with a stripped out shell from 1974 and backdating it to the earlier longhood look. (Backdated Porsche means to make it look older than it is). It’s not easy to build a car in a small garage but I hope to inspire other gearhead minded people like me to build something cool with DIY style.
In the first few episodes I will focus on the autobody metalwork to transform this junker into something fun to drive. Extensive metal fabrication is needed to give the body the wide and low stance that I'm looking for. Metal fab can be time consuming but its the detail that set each car project build apart from the rest. My classic Porsche strives to be unique with custom hotrod touches throughout. There will be some rust repair in the front trunk area including the infamous suspension pan...home fab style.
I plan to update weekly videos detailing the customization of my classic sports car. This is a low budget build so I plan to make many of the custom parts myself wherever possible. I hope you enjoy my car vlog that will hopefully become an autocross racer or track car someday.
Engine plans are 3.0L+ with individual throttle bodies ITB
Custom brakes and suspensions mods are also planned.
Please stay tuned for all updates on this project series.
Product and tools info at www.ahhgaragetime.com
My Classic Car Restoration Future Plans
I plan to modify the suspension and brakes with improved aftermarket parts from Elephant Racing and Tarett Engineering as money and time allows. Larger brakes from a late model Boxster will be used since this car didn’t come with any brakes and they seem to be the best bang for the buck. The engine will be from a later Porsche 911 to with at least 3.0 liters and I hope to use a custom individual throttle bodies with a modern injection system and software.
In other words, this build will be a mashup of all Porsche’s best years. The classic look of the early lightweight body with a more modern air-cooled drivetrain. Call it a restomod or hotrod if you like, but I’m going to make it my own with custom touches along the way. Please join me in this detailed restoration journey.
Porsche...there is no substitute
Visit my website at www.ahhgaragetime.com or
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Here’s a recommended book.
amzn.to/2HCD3BQ
![Strut Braces & Bars - Do You Need Them? [Car Handling Tips] Pros & Cons: Strut Bars vs no Strut Bar](/img/1.gif)
Wow I'm sooo glad to have discovered your channel!!! Totally love these empirical, real world tests!!! Lo'ts of great new vids to watch too, thanks!!!!
Great, are you also working on a similar car? New videos every Saturday!
@@GarageTimeAutoResto No, my current project is a restomod of a 1997 Ducati 900SS, which has been going on a for a few years.. usual time issues!! Next projects I have in line are resto / rstomod of a 1988 944 Turbo S and a 1997 BL Mini!!! Subbed and eagerly awaiting your next releases!
Sorry this video is so long. I tried to remove as much fluff as I could. Sometime the geek in me just takes over. This is a continuation of this seam welding video:
ruclips.net/video/RfDPUD-RhMM/видео.html
Please click here to follow the 911 build progress in chronological order (oldest to newest)
ruclips.net/p/PLO2EVK95VV2S3bxN-v3sx3SvJL9FgeZII
It really depends on the chassis and the strut bar. IF your strut towers are tied to the firewall/bulkhead/chassis within 10" or so, not so much. But an old mustang, civic, etc, and it can really help flex, specifically when putting big sticky race tires on. For the street, it is mostly adding weight.
Every car is different. This is a torsion bar car with a light front end. Strut bars do very little.
Absolutely one of the most spectacular car videos ever! I would like, with your permission, to refer this video to anybody who says I obsess too much about cars. Thank you.
Of course you can share, that's what it's for. As the edit for this video trudged along, I struggled to cut it shorter. I thought at least one person would enjoy the details so I left it long. Thank you for appreciating it as this video wasn't created for the masses. . This car sickness is super fun for me.
@@GarageTimeAutoResto Indeed!
Agree! Love the detail.
Thanks!
I installed a front strut brace bar in my 2015 Subaru forester Touring model. It is a single welded piece without nuts or bolts. I detected a significant difference in these cases: 1) high speed turns on freeway on & off ramps 2) lane changes on the freeway 3) bumps & dips in the road. with respect to turning, the front of the car stays flat and level. This can mean that the tires have a better foothold on the road. With respect to dips in the road, the front end dips together irrespective of which side the dip is on. This means that the strut bar is causing the left & right suspensions to move in unison. It definitely has a positive effect on turning which is proportional to the speed of the vehicle.
Thanks for your driving experiences. Your car is a totally different animal being front engine and coilovers. My 911 uses torsion bars whereas Subarus have springs that put all the suspension loads on the strut towers. Plus the mass of the engine adds a lot of forced to the chassis up there too. Many people have said that strut braces help on mustangs and BMWs. My point is that don't do much on old Porsches.
@@GarageTimeAutoResto Well, I can't afford a Porsche, new or old. Ironically, the Subaru has a boxer engine which came from Porsche, I believe.
Hey great stuff! I've always thought these things don't do a lot w/r to handling especially on a modern vehicle.
One thing to keep in mind is your test bar bolted underneath the car is also constraining the chassis. So it also added to the rigidity of the chassis. The true test will be driving it with the load cell installed.
That's coming😀
Great vid Tom. I think you are right, the 911 is pretty strong in this area. ‘Traditional’ cars probably benefit more as the engine creates a massive void between the towers. I used to run a track BMW e36 that showed significant improvement from adding the lower cross brace from a convertible. BMW themselves applied the same logic with their M powered cars. In a non-caged front engined car with McPherson struts linking the towers will likely yield benefits above those seen on the inherently strong 911.
Thanks Tom! You are right front engined coilover cars are a very different animal. A few others have noticed differences with triangulated braces to the firewall on traditional cars too. Great discussion has come out of this for sure!
I've got a strut brace in my car. In the engine bay there usual isn't a brace from the left hand side of the top end of the suspension to the right. So when you drive around a corner. Let's say your turning right. The right hand side suspension will drop down when your going in to the corner. But the left hand side suspension will stretch the spring up. Adding a strut brace to them both makes it act like in my opinion a seesaw. So you would get a seesaw efect so instead of the suspension acting freely going up and down every time you go around a corner. The strut pivits the force being pulled and pushed on the springs.
True, but for a 911 there isn't springs or a heavy engine. So it's a totally different animal. I think strut braces are much more effect on front engine cars with struts.
One of my fav videos so far.
Thanks, share it with everyone who has a Porsche! I need a few more critics, ha ha.
From reading the comments what it seems to be is that your car won’t benefit from it much but every car is different and some cars can see better results from a strut tower bar
This is true! My video was only about Porsche 911. Torsion bar and rear engine.
Maybe a retrying it and is there a second car to see if you can get the same results
Nice job Tom. Maybe consider adding threads and nuts (similar to a tie rod adjuster) to the strut tower bars, to allow you to preload the tension between the struts, one extra adjustment when driving.
Yes, that's what most of the aftermath bars have. The loads alternate between tension and compression, so I'm not sure why prefer tensioning is done. I always thought the heim joints were there for car to car variation?
Tks...tend to agree as I have brace on/ off Subaru turbo etc and don't notice great change...inside cages seem to gather more desired stiffness...^play^ in system escapes until stiff shocks hard/wide tires, and larger torsion bars then seems to focus on the ^soft^ plyable spots. Had a track karmann ghia years ago that did benefit from adding the convertible only rocker plate to my coupes rocker area...sorry just rambling. Enjoy your work and attitude
Thanks Steve, I totally agree that cages create the most stiffness. I'm not going to put a full cage in this car, so its kind of fun determining what changes do what. I also agree that the stickier and stiffer the setup the more stress the chassis experiences. The chassis can never be too stiff in my opinion. Let the suspension do the work is my opinion. Thanks for sharing your experiences!
Hi. Very interesting test. It was great to see it. I know it is chicken-egg like consideration, but the reason people were start using strut bars was not about the force but the deflection causing lack for correct geometry. So same force for different car chassis might create different change in the wheel alignment angles. The misalignment during strong cornering and rapid dynamic forces, not easy to generate (and even dangerous once they would be constant) are the main reason people are mounting. I think it can be calculated but if the fully loaded car is running 100mph and cornering, the forces are really huge. Also there is a risk that if the chassis would be too rigid it would brake in some other points. So for daily driving cars the elastic nature of car body is something also good for it's life. Race cars are scrapped much faster. So it is always a question os sport results and the lifetime. Anyhow I'm with you checking such topics. For me it showed static behavior for relatively low loads as car body can see during high speed and regular driving. Keep watching next videos! Thanks!
Thanks for your thoughtful comments. I hope to repeat this strut brace test now that my car is driving.
I made a recent video about shock forces and I do agree that the faster you go the higher the shock piston velocity and force become. However, the lateral forces don't go up much past 1G. They are usually less than 1G unless you have serious aerodynamic forces acting in your favor.
In terms of chassis fatigue cracks and race car chassis timing out, I have a different viewpoint.
The more the chassis flexes the more it will tend to crack. If the chassis is made stiffer then it will be less likely to crack. This extra energy will be consumed by the suspension as it should be.
Seem welded race cars typically last much longer than non welded cars.
Hey Sir, on our projects we almost always see that bottom X-frame is more beneficial compared to strut bar. Also, strut bar is much more effective when it is connected to cow-bell (Mid-under of front windows) too. You probably know these but wanted to mention.
Edit: Ok, I should mention that our aim was to improve first-response turn-in of the vehicle. Not steady-state turning induced rotational flex.
Are you referring the 911 X brace? If not what car are you referring to?
@@GarageTimeAutoResto Hello again, nice to have a reply. I cannot disclose but it is a SUV like bulky car.
@@GarageTimeAutoResto Wow, after 5 years I watched the same video unknowingly. And again, I have some more comments. I think the purpose of these kind of add-ons would be about frequency response of the vehicle, which mainly concerns on-center response which also translates to "agility" feeling. Total flex would also decrease to some point, that's true, but probably not the dominant benefit. Really appreciate your work one more time Sir.
As you suspected, I am also skeptical about throwing braces here and there. Especially if they are replacing steel with aluminium. I would guess that 2-point strut braces would mainly work on front engine cars during hard braking and acceleration whereas 3-point shows itself on torsional stiffness.
Good to hear from you again. There's been an update video with actual driving
ruclips.net/video/pbX9luG637M/видео.html
Great video, yes it does not makes big difference. Changing stabilizer bar size, bushings, and spring,/shocks gives better effects.
Yes! I like to stay start with things that are closest to the road. #1Tires/alignment, #2Springs/shocks,#3 ARB
Very good information. This is gold. Excellent video.
Thank you for watching!
This is awesome. Thanks for all the extra effort.
Of course, I'm glad you liked it!
Great informative video as always Tom... I enjoyed it greatly 👍 I do agree totally regards your ‘gains over $’ assessment regards to bolt-on bracing of the struts (same goes for any ‘bolted’ solution including roll-cages etc. I guess we can categorically state that if the test had of been conducted prior to seam welding then the gains would have been marginally greater but probably not more than 40%. What is evident is that there is no substitute for direct welding triangulated structures. P.S. I really liked how by complete accident, when you opened the smugglers box it aligned up perfectly with the top of the strut brace 🤗👌 You can now add a simple magnet to your final strut to hold the box open... now that’s a Win and surely worth all that time 🤪😂✅
I'd rather be lucky than good! A magnet is also a good idea!
It is 2023, we need an update to this 😁
Ok, will do. New engine going in MAC soon.
Did you consider jacking one side of the car up a silly amount? That would help load up the bottom of the tire to simulate cornering forces.
Very cool take on it. I admit my SC has a strut bar and maybe yes a little gimmicky 😅
Yep, I did Jack up on corner a silly amount and also dropped it. Super silly. Jacking at the wheel doesn't change things because there are no springs in the strut. Just fluid and a holey piston thing. The axial force in the strut only occurs during high speed bumps and corners.
Maybe if you put strain gauges on each strut tower brace and measured the deflection with and without the cross braces, that might give you a better idea how well it ties everything together. You could correlate it with the load cell data in tension & compression.
Yep, I agree and I do have some strain guages. I think I'm going to put those on the door sill area and see if they are sensitive enough to determine what spots need strengthening there. Ready to move on from the strut brace actually.
You can tow it behind another vehicle this is my first video of yours that I have seen
The car now drives, no need for a tow!
Awesome video. Appreciate all your work!
Thanks, I'm glad you liked. I learned something...
I guess the question is , with the change in camber through a corner without the brace, does that produce sort of a feedback loop force. Perhaps the lack of rigidity causes more tire deflection and then more tire deflection also causes a greater torsional force.
In a 911 torsion bar car you don't need to worry about the camber changing due to a lack of strut brace.
Two curved strut bars the top curving down. The bottom curving up and welded in the middle.
I like this idea of curvy bars! It has crossed my mind before too.
Pulling the car at the front is much more realistic since there would be cornering sideloads at the front of the car.....I fitted a 2 point strut bar to a Toyota Corolla and it did make the steering feel more direct and agile on corners. If you tried the strut bar before seam welding then you may have seen a bigger difference in rigidity.
Yes, I agree the side loading is what I was after. But after it didn't produce much load in the strut bar I tried dropping it, ha ha. That's cool you noticed a difference, maybe front engine cars have higher loads in the front????
@@GarageTimeAutoResto Yes I guess they would through more mass and drive being taken through the front struts....Good work on the scientific test
Nice job explaining all this 👌
Thanks!
A strut brace in your car. If you haven't driven you're car before with a strut brace connected up before. And you just put one on for the first time you can tell the difference in how much more control you have when going around corners. You don't need in my opinion go around a corner extremely fast to tell the difference. But since I've got one on my car and I've been driving my car for a while with it on. If I took it off now i would tell the difference in the first 30 minutes of driving the difference when taking corners. I'm not a race car driver even that i like my cars to look the part.
Great job thanks
Tom this going to be one hell of a track car ..😀
Thanks Brian, maybe someday.
The answer: No. But explained in an expectacular way. THANKS!
Expectacular! That's a cool word I haven't heard before!
Tom, another great informative video! I was wondering during your video about your overall approach to the topic. Meaning: You seem welded the front prior to your strut bar testing. Many people may not have the opportunity to seem weld, so how much difference does it make without seem welding for those looking for bolt on help? Just curious!
As always, I enjoy your project videos!
Shane
Hi Shane,
Thanks! My sequence of events was determined by the welding order. There are seam welds underneath the strut brackets. I think the torsional rigidity benefits are additive, so the order of testing doesn't matter. The load in the top bar does matter, and I agree it would be cool to know before seem welding. The take away message is buy the three point bar. Do some research on how the third point bolts on. I've seen some attach to the thin sheetmetal which does nothing. Does your car have a brake booster? Some attach to those but I'm not sure it's a good place to attach a strut bar either. It's buyer beware for sure!
Nice test. Maybe it's better to use that strut bar with that little device in the middle on a drivable car?
That's coming. The car in this video now drives!
Had the bottom brace hold the load.
Should of tested with no brace & anther test with just top brace.
Agree, there are endless tests that can be done on these things. I disconnected the diagonal brace and compared the results. There wasn't much difference which means neither bar is carrying much load. This did measure just the top brace. If I get more time when the car is driving I'll repeat this test on the track.
TKS. GOOD VID.
Hey thanks for watching
So, a strut bar should be mounted with a tiny bit of tension, “pulling” the towers towards each other?
Many people do this to get more negative camber, but it's not important as long as all the joints are tight.
Thanks for taking the time to do some empirical analysis. I found it very interesting but I feel just pulling on the front of the car does not induce significant side load. I understand that in the garage you cannot include all necessary variables. My thoughts being that when more factors are accounted for there will be much greater loads placed on the car and transferred to the strut brace and potential for greater deflection.
1. A car on the road has a greater weight than the car in your test.
2. You must account for the speed of the car in two planes (any downforce becomes a added weight) and in the force vector for the turn.
3. You also need to account for the coefficient of friction in the tires (warm tires with downforce weight will not slide as easily as the tires in your shop and load up the suspension and transfer more deflection.
Like you said it would be great to perform this test on the road. Just because there isn’t much benefit to the brace under the garage test loads does not guarantee that that the same result under cornering hard at a high rate of speed.
How about this for a final thought: A bolted in brace solution will become more effective upon being subject to a greater load. X amount of body flex is needed until all the play is taken out of all the fasteners , then it will brace more like a welded in solution. Just a thought.
Thanks again for all your videos.
I appreciate your thoughts and agree 100%. I will road test this rig, but I'm not expecting huge loads even with the best street tires. Suppose for the sake of argument that the dynamic corning loads are ten times higher than my garage simulation. Then that's between 50-100 lbs in the bar. I'm not saying the bar isn't useful because I already convinced myself that it has a torsional rigidity benefit.
I think higher loads on full race cars are likely when you consider aero forces, huge track tires, and competition style driving. A few people have mentioned that they have seen the early type bolt on brackets bend. Parts bend on race cars often and its not always certain how, when or why it bent. Could have been a crash or wheel to wheel incident???
The final thought about bolt on braces is probably true, but I didn't see any slipping in my test data. I've tested things before that slip and there is a distinct signature in the data when something slips.
Thank you for taking the time to share your thoughts and comments. My goal is inspire others even if its a mental excercise, ha ha.
Garage Time - Restomod
I guess since my wife and I track and autocross our cars that is where my mind immediately goes. I didn’t even consider street driving -driving (street driving is just the act of getting a car ti the track) I will be conscious this mistake. People use cars in many different ways. I enjoy your videos and analysis. We also have a 74 that we are reimagining into something new and am sure we are going to use many things I am learning from you.
great video! Since you've gone this far with the brace have you considered a second diagonal bar? (like an X).
Yes, I'm seriously considering adding more tabs to the other side and making an X like you say. That is why I'm trying to get all this chassis stuff done before I finish painting everything. It would be easy to add the tabs now, so I probably will.
Garage Time - Restomod - Ive seen some x bars that come from the strut tower points to the front two corners on the nose. They go over the tank and spare tire area towards the left and right corners on the nose. Is there any advantage to that? The front x section was removable
Yes, I was going to add those too, but now I'm reconsidering. The forces at the suspension pan pickups are in a different direction. Most severe during braking. I don't see much benefit of those bars, but then again the factory put them there for a reason on the RSR. It's a good question. Not sure how much more I want to play with strengthening mods. There are other more effective mods in my opinion.
Garage Time - Restomod RSR - hmm. Secondary forces that apply under more extreme conditions? Curious.
Yeah maybe, so if you look how the A arms is designed it puts like 99% of the vertical loads on the big crossmemember piece. The strut attaches in the same plane as the x member practically. So instead of an A arms, it's like a triangle. This means almost no vertical load happens on the suspension pan. And the braking loads are sideways. I don't see the X brace doing much for those side loads.
is there a chance that the low number may be caused by the already reinforced welding?
it may have a more significant effect on normal cars.
since not everyone have the guts, time, effort, or budget to seam weld the car, bracing might be the easier - and reversible - solution.
Every car will be different for sure. Since this 911 is a torsion bar system it doesn't require really strong strut towers.
If there's a V8 up there and coilovers then I think a strut brace is more useful.
Regarding the seam welding, the effects are additive. It doesn't really matter if I measure the strut brace loads before or after the seam welding.
It's only a precent change type of improvement.
Sand on sand off... Great video on the topic. Maybe an X brace would make better rigidity?
For sure, are you talking about the one over the spare tire or adding another diagnoal bar across the strut towers?
@@GarageTimeAutoResto one over the spare tire
it's not for everyone. But for my style driving i look to go around corners like my car is on a train track. And that's how I like my car's to handle
Try the same test with a cabriolet.
Exactly what I wanted to say ... the convertible chassis is definitely impacted when turning corners. So for cabriolet aka convertible the strut brace bar will improve.
nice tom do you tnink the results would have been more dramatic if yu had not seam welded the frunk? watched after SANDING THE BONDO OFF MY 928 BUMPER COVER jes sayin
Hey Joe, I did some sanding this week! How close are you to painting that 928? Yes, I think the force in the strut bar would be higher if the seam welding wasn't done, but not significant. Maybe 15% more on 70lbs, is still a small number in my opinion.
Did you ever repeat this test with the car on the road?
Not yet. But I will, preferably on a slalom course. It's just a low priority at the moment as I'm fixing transaxles and swapping engines.
All of mine have been triangulated to the firewall. Would that make an engineering difference in a Porsche?
Yep, triangulated is the way to go. Not sure why some brace back towards the firewall. Maybe it's a front engine thing.
The math says that with a front engine car the firewall tie in adds not only torsional but “front to back” strength, at least in an E36 M3. Watching your video I wonder if it’s because of the “empty space” that a Porsche is different. Love the videos
Dave Harris - had a 94 civic hatch back and loved to toss that thing around. On stock suspension you could feel the front end of the car twist under different engine load and grip conditions. + 3pt to firewall strut tower brace, 80-90% twisting gone - responsiveness increased tremendously. Interesting point.
Engine...nah
Towel warmer...hell yeah
Thank you. One less thing I'll have to buy!
Ha ha.
Respected Sir good vedio but I think we must consider the two factors also, speed and weight of car.
True, I'm going to repeat some measurements at speed. A front engined car with coilovers is a completely different scenario. More weight and more forces up high.
My summary is that strut braces don't do much on torsion bar 911's
The max lateral cornering forces are about 1G and doesn't really depend on speed much.
Would you recommend flexible strut bAr or rigid bar? I
Do you mean the adjustable bar with heim joints? I don't think any are flexible by design?
Subaru makes flexible strut bar. It has ball joints in middle covered with rubber.
Oh, I'm not familiar with why there would be rubber unless maybe it attaches to the engine?
Too bad that you cannot put it on a car that goes down the road
This car goes down the road now. Will try this test again, but don't expect any difference.
Surprised me
Me too, I was hoping the results would be more significant
No white lab coat...soooooo disappointed ;)
I love science!
If you’re an engineer, it would make sense to film your video just as a scientific journal and state your abstract first. Your intro is missing the findings, making this video “way” too long.
Watch at 2x then. I can only do what I think feels right. If you aren't interested, than so be it.
Your conclusion it is to a femely car ? My question is car like porch is very solid body from bigenin compering to a femely car.. so maybe your conclusion about it is right just for sport car and don't right for a femely car. Sory abut my bad English... Keep doing what you good with and thenk ahead
Hi, I hope I understand you correctly. My conclusions are only for vintage Porsche 911. The newer Porsche's such as the 964 model are much stiffer. My hope is to improve my chassis to be stiff like the more modern Porsches. A family car wasn't really considered in my testing.
First
first reply
Completely off base, you measured it when it wasn't driving. The point is a compliant and predictable setup. Stiffening is simply one effect of the bars. Keeping the flex from a wide to narrow band to give the driver confidence, to minimise understeer or oversteer..you didn't measure any of that, you must be one of those unemployed engineers that doesn't understand what a car is used for....it's not a house..that cracks when it flexes and needs to be on a solid footing...it's a car with moving parts....that's meant to tilt and flex,,. It's about predictability!...did you measure the flex range? Did you measure the angle variance when driving at a certain predetermined speed over a consistent path? ....no???...then don't give advice , stick to designing floor joists or roof trusses.
As I said in the video I will continue testing when driving on a track. This car now drives, but the strut bar is a low priority. It does very little on a 911. I made no claims or gave advice about other front engines coil over cars.
Oversteer or understeer isn't controlled by a strut bar. This is exactly my point! People buy this stuff and expect it to perform miracles.
There are no measurements out there, so I gave some data for free. If you don't like that, then go buy a strut bar.