Suspension Optimization: Geometry and Bump Steer. Ep. 83
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- Опубликовано: 16 окт 2021
- This video covers the process that I went through to get the suspension geometry hard points analysed and optimized to meet our target goals. In the last video, we got the suspension gross correction done using manual methods. This time, we employ some suspension software to move the hard points to get the final values dialed in.
I hope this one help.
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Never apologize for making sure your steering is correct. It protects you and others on the highway. I enjoy your videos, always informative.
Thanks 👍
Was going to write some BS about suspension but I don't need to, you nailed it. The true art of suspension is getting it to where you want it to be and knowing what your end geometry should be. Well done. All this will pay off on the alignment machine.
Thanks Tony - I really hope so.
I think i just learned more about suspension than i may have ever needed to know... Awesome! Your work is always top notch.
You and me both. Then again most people I've talked to that have gone this deep say they really don't need to do this again. Like once was enough.
Excellent series! I imagine afterward anyone would be a bit mad, but that understanding of how the suspension actually works, means when your driving you'll have a real understanding of what the car is and why. I'd imagine that's more satisfying when its your doing and hard work that made it possible. Well worth the headache in my opinion.
Yes - it's just a few more steps back than I was hoping for, but now I know a few more things.
I'm a mechanical engineer in the US, metric is the way to go for engineering, absolutely. For building stuff, i do find it easier to us SAE though, annoyingly, lol.
Also, thank you for such a great series. I hope one day to build my own car like you're doing. Next step for me is to get a house with a garage/shop! :)
Cheers - I'm saving my pennies for a new garage...this phone booth is a struggle.
Incredible work!
Thank you! Cheers!
Great video. This is one I will go back and watch several times.
Glad you've found it useful Paul.
Awesome info! Thanks for sharing what you've learned
Glad it was helpful!
Awesome summary 👍👍😎👍👍
Thanks! 👍
Must be satisfying getting suspension sorted properly. Thanks for sharing.
It was fun to get the last of it done...for now.
Well done sir, glad you nailed it now build so we. An see that big smile when you drive it.
Fingers crossed!
Good on you for seeing the problems then correcting them.
Thanks. Just seemed to make sense.
Good job, will be interesting to see how it works out on the car. 👍
Fingers crossed!
Yes!! This is what I wanted!
Glad it helped.
happy to see you back and still at it.
Thanks - I'm not going anywhere...work is nuts and this has been bonkers hard, depressing, and unpleasant. Moving on this week as parts are ready to get sent out and I shift to other projects for a bit.
@@ThrottleStopGarage hello again- is there any chance you might have some more tuques for sale? I knew I should have got one or two when I had the chance. Thanks.
@@lannysanders6043 I'll make sure they are available in the store later today. 😉
Smashing
Thanks!
You're welcome!
Outstanding, thanks
L / S
Glad it was helpful.
Optimization is just the beginning! Important step before tuning will be accurately and correctly transferring all of your mounting points onto the car. Tuning may just cost you some of your hair! 10:17 Poking fun, but TRUE!
I can't wait to tune! That will mean it moves.
@@ThrottleStopGarage When you are tuning and pulling out your hair, just look back to this comment and try to recapture some of your excitement!
LOL - I've got only a little hair left (COVID haircuts FTW). I've already got the suspension sorted out in Fusion 360. Brackets, bushings, spacers...fingers and toes crossed as it's being sent out for machining this week. Both upper and lower elements were designed about 4 or 5 times each. That will be a fun video.
@@ThrottleStopGarage Looking forward to it! Bring it to Winnipeg when you are done. I would love to see it in all of it's glory!
@@kentmckean6795 That's an absolute certainty. I'm a native manitoban from Brandon. Can't wait for a blast across the prairies.
Interesting stuff with all the roll center (mis)information on the internet. My 2022 GR86 measurements, from the garage floor, for the rear LCA are 7 and 3/4 at the hub and 7 inches at the LCA connection to the subframe. UCA at the hub is 15 inches and inboard is 13.5. 61 inch track width. The distance between the center of the 2 bolts of the LCA is 17.75 inches. So by my sketch/calculation my Roll Center is basically on the pavement. Hmmm. I will lower and raise the suspension and test it the old fashioned way. Lap times.
Articulate the suspension and measure the centre of your contact patch. That curve gives the RCH. For your strut front suspension - on the pavement is pretty normal for strut style IFS.
Always look forward to your videos. So meticulous too. If you just cobble stuff together who'd care?
Thanks - I was taught that craftsmanship was the gift you gave yourself!
I know I am hella late to the party with this one, but they do sell high travel balljoints for most GM upper applications. Speedway Motors carries quite a few.
Not late at all. I'm just building the jig to try this all again. I should be fine with the travel I've got with the standard ball joints. I will look these up though - thanks!
Sorry I missed this. Maybe I should turn on notifications.
Ring the bell!
I would love to pick your brain, because I'm just a guy in a garage too. I'm trying to get my setup right and I'm running into the same problem that you are with getting stuff machined. Nothing is offered for the 2nd Gen Colorado's except a Belltech lowering kit which leaves a lot to be desired. I thought that my bump steer stud that I had made was wrong, but after seeing your spindle it appears as though a bump steer stud will work even if it's not perpendicular with the ground. My stud sticks forward of the vehicle and a little bit in and I was getting terrible bump steer worse then before so I took it off and put the stock inner and outer tie rod back on.
Question #1 What type of inner tie rod end are you using? The factory has a long rod link that screws directly into the outter tie rod. If I could find an inner tie rod with a reverse 3/4“ thread then I would be in better shape. The only thing I found for our trucks is a inner clevis kit which causes clearance issues with the rack without using the long travel suspension that the company offers to use with that clevis kit. It effectively reduces your steering radius. Don't want that on a lowered Street truck. Doing U-turns can become a three-point turn.
Question #2 what software are you using to put your measurements in? That would help me out greatly. Thanks
The steering for my car is from Woodward Steering and is custom made for my application. They fitted the inner tie rod end is a monoball of their design. The outer is a heim joint (spherical bearing) from Aurora. I just use Google Sheets in the garage on my old laptop. It's like Microsoft Excel, but free.
Thanks for sharing.
But................. Projecting a laser line onto a vertical surface to check bump steer doesn't allow for changes in track width as the arms move through their arc. You may have more or less bump steer than you've interpreted.
There is a good video on RUclips where some British guys bounce the laser off a mirror and back onto a vertical surface attached to the wheel hub, to measure bump steer. This allows for track width change.
Your modeling hasn't shown the effect of the caster angle on negative camber gain with steering lock.
When Google looking for what would be a preferred caster angle for a suspension design/system, about the only thing that I did find was a comment that the caster angle should be greater than the steering axis (or kingpin inclination) angle.
The greater the steering axis angle, the more it 'dilutes' the negative camber gain with steering lock.
So if you have, say 6* of steering axis angle, then you should have 'more' than 6* of caster. How much more? I don't know.
Obviously as change your static camber angle, you'll change the steering axis angle.
Ackerman angle.
Definitely something you'll want to get right, especially if you plan any sort of vigorous driving in tight turns.
Having the steering rack mounted as close to cross member like you did on the bench model, has the outer tie rod ends further forward than the inner tie rod ends. This could negatively effect the Ackerman angle.
And that's assuming the Ackerman angle is going to be correct when you are using Corvette parts in your Volvo.
If the Ackerman angle is correct in the 'vette and the wheel base and track width are very, very close in your car, then it should be OK. But that rack mounting location could induce some negative effects to the Ackerman angle.
Keep up the good work.
I see what you're saying - but I already know the lateral movement of the contact patch over the range of motion of the suspension. Basically - it's a compound measurement - this also doesn't matter as the suspension is as it would be on the car, if it toed in or out in a direction not related to the lateral contact patch, that would be a problem. I was able to adjust the shim under the bump steer corrector and it did what it was supposed to do. Software simulation indicated almost zero. I'm happy with where it's at.
The rest (Ackermann etc) has been measured for this car. It does share the wheel base of the C4 though the track is different. The rack is lower and non of this was a guess. I needed to move the rack forward a little as I shifted the UCA to correct castor but didn't shift the rack.
I've not seen the reference to the SAI vs castor relationship. The stock SAI is 8.4º and the suspension runs 7º. When I was running the software simulations - 7º was what kept working. So that's where it's set.
So if there is more I have to read - shoot - please.
What was your antidive angle as well as it angle of your upper control arm and the lower control arm you mentioned 7° castor i’m really doing the upper control arm on a 97 Pontiac Firebird for auto cross thank you
The antidive is set to 40% - the upper arm is inclined 11.3º. I'm not sure how this information will help your set up.
Thank you,
For someone who doesn't have the equipment and software, what process do you suggest one use to properly setup suspension (track and street purposes). What parts should I start with and adjusting from there assuming the below components will be used on a stock car (in this case, a c6 z06)?
Splitter, rear spoiler, coilovers, swaybars, lower ride height, higher grip tires
Do you race? If you do, then carefully read the rules for your class. If not, then tires - pretty much just tires for a C6. Get a 4 wheel alignment and ensure that everything is in good condition. The rest you have to evaluate what the car needs for the track you're at - tires...did I mention tires? Brake pads. The rest of what you mention is fine for the last tenth - but most is pretty low return and most drivers don't push their cars to the limit (this always causes hurt feelings) - but at that last corner, did you have to catch the car from spinning? Nope...push harder then...then add aero or more spring or more ARB. Cars that are good on the track are rarely nice to drive on the street and street cars rarely get driven very hard on a track.
@@ThrottleStopGarage thank you ! I am planning to start racing here in a few months, I am completely new to the world of car performance and just doing my research to avoid some common pitfalls newbies run into, I like to map out a long term strategy and your input really helps. My goal for the car is 70% track 30% street just don't want to go to crazy and then my wife would hate riding with me 😂
Excellent - have fun. For a first-time driver, get decent ultra-high performance tires (Bridgestone RE-71R's or equivalent). Make sure your maintenance items are up to date and get track focused brake pads/rotors. Check alignment and if there are no class restrictions - try a little more negative camber (-1 deg for a C6 would be tons if possible in the rules). Get something to measure tire temps and NOT a thermal gun - but a probe you stick in the tire to check actual temperatures. Then tune from there. Honestly, have fun - learn lots and get a driving course at the track if possible.
not sure if he is still doing it, but elmer racing was pretty good at taking on one-offs back in the day.
Not cheap, but it wasn't a "go away" price either. That may have changed as he has grown. Not sure.
So you took a c4 front suspension and want to use it on the old Volvo.
Was the optimization for the Volvo's mass and dimensions (wheel base, roll center etc etc), or was the optimization for an arbitrary preference for some sort of driving style?
In other words were you making it kinda neutral relative to the Volvo or were you shooting for something specific?
Short answer - Yes...the two cars have the same wheelbase but a different track. The mass is an estimate for this build (as is CG height etc) - also the reason I was taking some of the anti-dive out of the suspension. The C4 is a low travel design and I was targeting values more appropriate to the sedan I'm building. I don't like cars with a lot of roll/dive so I've worked that into the design. So this is a lot different for the Volvo but also not a copy of the C4. And I'm only hoping I am getting it right - zero guarantees on that front. I've never done this sort of thing before.
@@ThrottleStopGarage ok I think I see what you mean.
I really like your engineering approach. You willingness to do all the tedious work will probably pay off huge!
One more question, since you said you are doing some fabrication, would it have been faster to design a completely optimal system (on computer), and then just get everything made to spec? -- probably more expensive, but would that be faster?
@@moesizlac2596 I do hope that the work pays off. It for sure would have been faster to design from first principles. I just do not have enough experience to attempt that level of engineering. I'm not sure it would be more expensive...probably less. In the end, it's an option for future suspension development if needed - but that is also a way down the line and only if something else goes horribly wrong. This is the hard way to learn for sure.
Bump steer will be the relationship between the normal arc of the suspension compared the the arc of the suspension with the steering connected. It appears your measurement was a combination of the two.
Yes, the measurement I made contained both components. I didn't see the point in measuring it otherwise.
@@ThrottleStopGarage that is fine but technically you are not measuring bump steer. Bump steer is the difference between the normal suspension arc and the arc with the steering connected.
do you have power steering? I was never concerned with caster because power steering handled it really well.
Yes - the steering rack is a Woodward racing rack. Concerned with the effect of castor in dynamics. Too much can kill caster as well as create upward forces.
@@ThrottleStopGarage ok gotcha. Miatas are all I know, and caster improves traction in corners out past 15 degrees. I can imagine that 13 would be too far for some geometries.
Why did you want to dial the anti-dive out?
These anti features are designed to transfer load from springs to links - I'll cover some of these details in the next video (coming soon). Too much and the suspension is basically binding. I didn't want all the anti-dive out - but it had more than I thought it needed.
@@ThrottleStopGarage Very curious to learn more in a future video!
Great info, how do you get it on the car exactly correct?
Ps, I just got a mill to keep my lathe company...🤫
There will be a jig to get the frame built and another that is already in the car. Maybe a little swearing. Probably beer. I wish I had the space for some proper machining tools. Just getting models sent out for quotes.
@@ThrottleStopGarage I'm sure you'll get it perfect
@@ThrottleStopGarage jw, what is your beer of choice?
@@AndyFromm can't say I have a favorite...depends on season and mood.
imperial is for wheels and TV's
And 2 X 4's.
Almost all products are designed in mm these days, because parts come from all over the world nowadays. Even though I'm in the U.S. I do all my design work in mm, and my market for my business are old German cars that are all in metric to begin with. I get really upset when I buy an aftermarket part that should be in metric, and is in SAE, and I have to dig out my SAE tools, instead of my metric tools for everything else.
That's my scenario as well...imperial just comes up so often as a criticism. This old Volvo was designed in metric as were the parts I've put on it. So it makes sense to me.
Hey, if you happen to be near Hamilton Ontario, can you drop by and figure out my entire rear suspension for me please, hehehe. I really need to learn some 3d simulation software stuff.
LOL - sorry - trapped in Alberta.
@@ThrottleStopGarage Hey, it was a long shot. I need to fabricate some control arms to convert an RX7 rear end to my Lotus 7 project, because I love to torture myself.
@@ThrottleStopGarage, lol, depending on what the travel restrictions look like in a few months, I'm probably flying up to Calgary. Let me know if you need something smuggled north of the wall. :D
@@chaseweeks2708 thanks!
Metric or Imperial? Use whatever you're comfortable with. But make it easy on yourself and stay away from the fractional measurements. That stuff is for guys who work in wood!
actually they are turnring into metric to.
When I did construction work, we'd always look for kids to help that were good at math because they had to divide fractions and not have their heads explode!
Wait. Theoretical doesn't always work in the real world? Hmmm. Obviously you don't work in govermental planning!
Clearly.