While on the topic of toe. When you did the toe plot against compression for the front, do you know if plates that added just positive caster (staight forward and back, not angled or horizontle) had an effect on the toe under compression? Or was it only when you messed with camber it had an effect.
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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I'm not sure because I only modeled the one situation. If I had to guess though, I would say that if you moved the strut only in caster and not in camber/kingpin, it would not affect toe much. However, if you were to increase camber/kingpin and not caster, it would have more of an effect. This is because the greater angle (kingpin) the strut is at, the more the attachment point for the outer tie rod moves inward with suspension compression, thus creating more toe in.While on the topic of toe. When you did the toe plot against compression for the front, do you know if plates that added just positive caster (staight forward and back, not angled or horizontle) had an effect on the toe under compression? Or was it only when you messed with camber it had an effect.
This post is so golden I am extremely surprised that it isn't 10 pages of discussion.
Yeah, surely changes to the caster angle impact toe, but not nearly as much due to the plane.I'm not sure because I only modeled the one situation. If I had to guess though, I would say that if you moved the strut only in caster and not in camber/kingpin, it would not affect toe much. However, if you were to increase camber/kingpin and not caster, it would have more of an effect. This is because the greater angle (kingpin) the strut is at, the more the attachment point for the outer tie rod moves inward with suspension compression, thus creating more toe in.
bump steer: happens going over bumps, pot holes? tracks and autox's are generally not that bumpy.
Ha, not quite. "bump steer" as it is called, simply refers to the fact that the wheel changes toe angle under suspension compression. For example, under braking, the front dives/compresses causing the wheels to toe in (rather excessively too).bump steer: happens going over bumps, pot holes? tracks and autox's are generally not that bumpy.
I'm not sure where you are driving at, but most tracks are plenty bumpy enough, at least in the US.
Bump steer is kind of a confusing name, as it has nothing to do with actually "bumps" in the road... but the "bump" stroke of the suspension(ie: compression).
I generally refer to it as "toe steer", as it tends to have a more intuitive definition.
I generally refer to it as "toe steer", as it tends to have a more intuitive definition.
Anybody race without power steering? I find it a lot easier to feel the bump steer without power steering on the RSX.
do you prefer the feeling of no power steering?Anybody race without power steering? I find it a lot easier to feel the bump steer without power steering on the RSX.
No it's terrible.do you prefer the feeling of no power steering?
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.
No it's terrible.do you prefer the feeling of no power steering?
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.
Ironically, my power steering FAILED a week ago on track. The high pressure output line blew and it spewed fluid ALL over the engine bay. Good news was I was able to get it fix that night (2am...) and return to drive again Sunday.
Personally, I would not even have driven the car on track had I not been able to fix it. Far too much effort to steer and it really didn't seem safe.
Personally, I would not even have driven the car on track had I not been able to fix it. Far too much effort to steer and it really didn't seem safe.
I need new coilovers soon. I'll be reading and re-reading this until I make a choice. Great thread. Bump so others can see it.
Bump cuz I just found this and I'm looking for anew setup next season.
Common, share with us, what are your plans?
Haha honestly no plans as of now. Waiting for 2012 rules to come out to decide whether to continue with STF, go all out in street prepared, or find a different car.Common, share with us, what are your plans?
I'm expecting when the rules come out they will accomodate drivers that choose to use wider tires in STF *crosses fingers* I don't want to have to change too much for next season but I will if I have to, or just get more involved in trackdays than autocrossing.
for some reason I had assumed STF would go by the same rules that were in place this year for ST. Wider wheels and tires sure would be great, 9" wide with 245s, oh yea!!!. I am due for a new set of tires this year. When will rules be finalized?
I liked the Star Specs and was planning on purchasing another set for 2012. Anyone have a better tire in mind for STF?
I liked the Star Specs and was planning on purchasing another set for 2012. Anyone have a better tire in mind for STF?
"- Give competitors a wider variety of solutions to the allowed modifications" In the rule proposals it gives this quote which leads me to believe they will accommodate those that choose to go wider, at least I hope so.
Although from over a year ago, thanks dude! :thumbsup: Looks like some of the reports we have to write in EE. Definitely informative. I found it especially interesting how relocating the steering rack increases bump steer.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.
Fantastic information here. This confirms a lot of my findings via my old school paper claculations and sketches haha.
Per my own work I also found that tie rod angle was crucial, and simply "flattening" them out made no sense at all. I have been working on fabricating a series of tie rod brackets in offsets of .125, .25, and .5 inches (in relation to Z axis). I always thought that the brackets we see offered here and there were way to agressive. Hopefully Ill be able to use one of my brackets to find that sweet spot that matches the arc of the tie rod and LCA as closely as possible.
For anyone lucky enough to afford a built to order suspension like Koni 2 ways or moton, it is very easy to tune this angle via the threaded tie rod arm. You are left with infinite options for tie rod placement.
Per my own work I also found that tie rod angle was crucial, and simply "flattening" them out made no sense at all. I have been working on fabricating a series of tie rod brackets in offsets of .125, .25, and .5 inches (in relation to Z axis). I always thought that the brackets we see offered here and there were way to agressive. Hopefully Ill be able to use one of my brackets to find that sweet spot that matches the arc of the tie rod and LCA as closely as possible.
For anyone lucky enough to afford a built to order suspension like Koni 2 ways or moton, it is very easy to tune this angle via the threaded tie rod arm. You are left with infinite options for tie rod placement.
41 - 60 of 107 Posts
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