Yes thank you big time for this. Took vehicle dynamics last year too and applied alot of similar info to our FSAE suspension.....too bad we forgot to sand one side of the carbon tube of our rocker link and the epoxy slipped right off and caused the whole damn wheel to fall off.....cheers to building race cars with not enough money, time, or personnel. Well least we can say we built one.....and that for a little while we actually had fully carbon outboards; a-arms, steerin linkage, toe linkage, half shafts, and rocker linkages.....Too bad my phone got stolen with all the damn pics haha
RSX Suspension Modeling Results
I recently took a vehicle dynamics class. We needed to do a class project, so I (and two additional group members) chose to model the RSX suspension. I am attaching the final report so that everyone here can benefit from it. Note, I am posting this here in the autocross forum rather than the suspension forum because it is more relevant to those of us who track our cars or do autocross.
Basically, the car's suspension was measured so that the location of every suspension point was known in x, y, and z coordinates. Next, the suspension was modeled in Solidworks. From this point, lots of info can be measured/calculated.
Anywho, we looked at camber gain, both from suspension compression and from steering input. We also did roll center heights and bump steer. All of these were done for the front and rear. Additionally, aftermarket modifications were 'made' to the model and their effects on the above parameters analyzed. The modifications made were roll center adjusting ball joints, caster/camber plates that move the strut top inward 3/4" and rearward 3/4", raising the inner tie rod ends 1.25", and lowering the inboard side of the rear top link of the rear suspension 3/4".
DISCLAIMER: Every attempt was made to be as accurate as possible during this project. However, it is exceedingly difficult to measure the suspension perfectly. As such, I do not guarantee any values as being 100% exact. They should be pretty darn good though.
Basically, the car's suspension was measured so that the location of every suspension point was known in x, y, and z coordinates. Next, the suspension was modeled in Solidworks. From this point, lots of info can be measured/calculated.
Anywho, we looked at camber gain, both from suspension compression and from steering input. We also did roll center heights and bump steer. All of these were done for the front and rear. Additionally, aftermarket modifications were 'made' to the model and their effects on the above parameters analyzed. The modifications made were roll center adjusting ball joints, caster/camber plates that move the strut top inward 3/4" and rearward 3/4", raising the inner tie rod ends 1.25", and lowering the inboard side of the rear top link of the rear suspension 3/4".
DISCLAIMER: Every attempt was made to be as accurate as possible during this project. However, it is exceedingly difficult to measure the suspension perfectly. As such, I do not guarantee any values as being 100% exact. They should be pretty darn good though.
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61 - 80 of 107 Posts
Wow, am I more confused than ever now lol. So my mods include n+, progress adj rear sway, skunk2 RLCA. Camber F-2.5, R-2.0, toe 0. For some reason the car just doesn't handle all that well. I'm sure its my choice in very shitty tires but thats all that I could afford at the time.
How ever, with the car lowered to about 1.5 finger gap, and on stock tie rod ends, the shop said that the longer ends were way too much and they couldn't get toe close to 0 at all. I was thinking that my tie rod angles were too aggressive and was thinking about ordering 0851's bracket, but now after reading this thread, that would actually harm handling more? Basically the same principle applies with inverted ends too right?
I mean other than what I have done, basically the only thing really left to do that will make the car handle any better is just tires and maybe pulling the rear camber back down to -1? Or is there something else? I don't really want to mess with custom spring rates though, but how ever, I would like to have a better handling car as I'm looking to do a couple of track days but not a full blown race car.
How ever, with the car lowered to about 1.5 finger gap, and on stock tie rod ends, the shop said that the longer ends were way too much and they couldn't get toe close to 0 at all. I was thinking that my tie rod angles were too aggressive and was thinking about ordering 0851's bracket, but now after reading this thread, that would actually harm handling more? Basically the same principle applies with inverted ends too right?
I mean other than what I have done, basically the only thing really left to do that will make the car handle any better is just tires and maybe pulling the rear camber back down to -1? Or is there something else? I don't really want to mess with custom spring rates though, but how ever, I would like to have a better handling car as I'm looking to do a couple of track days but not a full blown race car.
So the shop said your longer tie rod ends were too much? What longer ends are you referring to? If your tie rods are too long for the rest of your setup. If this is the case were they able to bring it back to 0*? if not and it is toed in that is most definitely a big part of your handling problem.
Wow, am I more confused than ever now lol. So my mods include n+, progress adj rear sway, skunk2 RLCA. Camber F-2.5, R-2.0, toe 0. For some reason the car just doesn't handle all that well. I'm sure its my choice in very shitty tires but thats all that I could afford at the time.
How ever, with the car lowered to about 1.5 finger gap, and on stock tie rod ends, the shop said that the longer ends were way too much and they couldn't get toe close to 0 at all. I was thinking that my tie rod angles were too aggressive and was thinking about ordering 0851's bracket, but now after reading this thread, that would actually harm handling more? Basically the same principle applies with inverted ends too right?
I mean other than what I have done, basically the only thing really left to do that will make the car handle any better is just tires and maybe pulling the rear camber back down to -1? Or is there something else? I don't really want to mess with custom spring rates though, but how ever, I would like to have a better handling car as I'm looking to do a couple of track days but not a full blown race car.
what do you mean when you say "the car doesn't handle all that well". too much oversteer, understeer? Low overall grip very well could be attributed to the tires. Driver, Tires, alignment in that order determine car perfromance so your tires are a major contributer.
I forget which parts I ordered, there was a thread on here that suggested them and I ordered a set from O'Reilies and when I went to the shop they were too long to bring it back to 0. So they put the busted stock ends back on it and brought it back to 0 and ordered a new set of ends and swapped them out for me and then installed and realigned.
The car seems to understeer pretty bad, as well I'm on the stock wheels currently and just some "decent all season tires" nothing sporty really. The toe is set to 0 front and rear. I was planning on getting a set of 17x9's and adding some 255's but that process has been delayed.
If I were to go to 1/32 out, would that really make a big difference?
The car seems to understeer pretty bad, as well I'm on the stock wheels currently and just some "decent all season tires" nothing sporty really. The toe is set to 0 front and rear. I was planning on getting a set of 17x9's and adding some 255's but that process has been delayed.
If I were to go to 1/32 out, would that really make a big difference?
Thanks for this thread, much needed information
I forget which parts I ordered, there was a thread on here that suggested them and I ordered a set from O'Reilies and when I went to the shop they were too long to bring it back to 0. So they put the busted stock ends back on it and brought it back to 0 and ordered a new set of ends and swapped them out for me and then installed and realigned.
The car seems to understeer pretty bad, as well I'm on the stock wheels currently and just some "decent all season tires" nothing sporty really. The toe is set to 0 front and rear. I was planning on getting a set of 17x9's and adding some 255's but that process has been delayed.
If I were to go to 1/32 out, would that really make a big difference?
Well if youre stock ends are at the point where they have play, that could most certainly affect handing, because now youre not only running 0 toe, but possibly +/- .1 in our out or both.
Also, what is your front camber like? A degree or more of negative front camber changes the turn in characteristics greatly, and gives a much more confident feel while cornering - as if you can "trust" the front of the car to stay planted.
I would recommend 1/32 out for a car that sees performance driving. I run my car at 1/32 out as well as alot of the cars i set up at work (some up to 1/16 out for certain tracks/drivers) The only side effect will be slightly increased toe wear, but if youre like me, thats a small price to pay for the added sharpness of turn in gained with the extra toe-out.
tires make a gigantic difference. I have been on N+'s with all season tires and it was horrible. Handling improved greatly once I upgraded to soft compound tires.Wow, am I more confused than ever now lol. So my mods include n+, progress adj rear sway, skunk2 RLCA. Camber F-2.5, R-2.0, toe 0. For some reason the car just doesn't handle all that well. I'm sure its my choice in very shitty tires but thats all that I could afford at the time.
How ever, with the car lowered to about 1.5 finger gap, and on stock tie rod ends, the shop said that the longer ends were way too much and they couldn't get toe close to 0 at all. I was thinking that my tie rod angles were too aggressive and was thinking about ordering 0851's bracket, but now after reading this thread, that would actually harm handling more? Basically the same principle applies with inverted ends too right?
I mean other than what I have done, basically the only thing really left to do that will make the car handle any better is just tires and maybe pulling the rear camber back down to -1? Or is there something else? I don't really want to mess with custom spring rates though, but how ever, I would like to have a better handling car as I'm looking to do a couple of track days but not a full blown race car.
Mark, what you are describing isn't bumpsteer but rather Tram lining / tracking.No it's terrible.
I get fatigued so easily both mentally and physically. It's even worse when I had to do half a day in the rain... as the car skips over larger puddles of water it tries to rip the wheel out of my hands.
Tracking has more to do with differences in rolling resistances at the wheels rather then toe changes. Typically the easiest way to tell the differences is whether or not the steering wheel jerks when it happens.
With bumpsteer the steering wheel its self isnt going to move/react to the change in toe, even though the car is going to act as if there was a steering input (it tries to change direction). With tracking the steering wheel will jump/jerk as the car reacts to a drastic change in rolling resistance between the two front wheels.
Wow, am I more confused than ever now lol. So my mods include n+, progress adj rear sway, skunk2 RLCA. Camber F-2.5, R-2.0, toe 0. For some reason the car just doesn't handle all that well. I'm sure its my choice in very shitty tires but thats all that I could afford at the time.
Seems like you've over stiffened the suspension past what the tires require.
Remember, there is a big difference between tuning the amount of grip a car has and tuning the cars handling balance. And stiffening the suspension past what the tires would require just means less overall grip (Higher suspension frequency = lower mechanical grip)
So, I'd ask is the cars problem a balance issue or a grip issue.
So I had a friend let me put his wheels on with some direzza's and holy effin dog balls what a difference. I def. agree that I probably have the rear sway too stiff, so I'm going to move it forward tomorrow.
I have since then replaced the worn out ends with new stocks. My front camber is -2.5.
I have since then replaced the worn out ends with new stocks. My front camber is -2.5.
Ah, seems as though Zzyzx called it with the frequencies!
^+1seems like you've over stiffened the suspension past what the tires require.
Remember, there is a big difference between tuning the amount of grip a car has and tuning the cars handling balance. and stiffening the suspension past what the tires would require just means less overall grip (higher suspension frequency = lower mechanical grip)
so, i'd ask is the cars problem a balance issue or a grip issue.
Bump for a thread with great info.
I have a question for you guys. I recently purchased the 0857 steering arm bracket and after reading the info I'm wondering if I should still install it or not. My car is just a daily but I would like it to handle as best as possible. After lowering the car on progress coilovers the steering became sluggish and unresponsive. I've also noticed a lot of tracking (steering wheel jerking towards the bumps in the road), especially after I put on the 255s. Will I benefit from installing the bracket? What can I do about the tracking problem?
I have a question for you guys. I recently purchased the 0857 steering arm bracket and after reading the info I'm wondering if I should still install it or not. My car is just a daily but I would like it to handle as best as possible. After lowering the car on progress coilovers the steering became sluggish and unresponsive. I've also noticed a lot of tracking (steering wheel jerking towards the bumps in the road), especially after I put on the 255s. Will I benefit from installing the bracket? What can I do about the tracking problem?
for the most part the same things that make your car handle better will also make the tracking problem worse, such as wide, sticky, low profile, tires, lots of neg. camber and toe out. I have just learned to live with it and realize it is the price you pay.
how wide are ur front tires?for the most part the same things that make your car handle better will also make the tracking problem worse, such as wide, sticky, low profile, tires, lots of neg. camber and toe out. I have just learned to live with it and realize it is the price you pay.
this is the reason i'm selling my 255s tho...
it is insane just daily driving.
I run 225s, but only because the restrictions in my class in AX.
What width and offset are your front wheels? Also how much camber are you running and is it added in via a camber plate or bolts? Like said before large tires, neg camber, and toe out will all make for a less than desireable highway feel, but scrub radius will enhance all of those effects greatly. Scrub radius is the distance between where the KPA intersects the ground and the tires centerline. If this distance it too large ie. a wheel that is too wide with too low an offset, it creates a moment arm at the wheel that amplifies any kind of tracking issues.Bump for a thread with great info.
I have a question for you guys. I recently purchased the 0857 steering arm bracket and after reading the info I'm wondering if I should still install it or not. My car is just a daily but I would like it to handle as best as possible. After lowering the car on progress coilovers the steering became sluggish and unresponsive. I've also noticed a lot of tracking (steering wheel jerking towards the bumps in the road), especially after I put on the 255s. Will I benefit from installing the bracket? What can I do about the tracking problem?
I am running 245's on 17x9 +35 wheels with -3.5 camber and 0 toe. No tracking issues here, unless the road is VERY rutted. if its a reasonably smooth road the car tracks well, even with stock caster. Before I learned most of what I know now I had made a custom tie rod relocation bracket. As soon as I installed it bump steer was atrocious. I immediately took it out and let my tie rods sit at their natural angle, with very little bump steer.
I'm running 17x9 +33 with 255s. My front camber is at -1 until my next which I'll probably push to -2. I'm using camber bolts.
Bump for the answer. Should I install the bracket still?
61 - 80 of 107 Posts
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