I've always been interested in suspension setup and in particular how much to lower the car for optimum handling as well as how much rake to run (how much to lower the front vs. the rear).

Of course alot of pure ciruit cars run very very low which would imply that lower is better but at the same time there's been much talk of roll centres and that Evos in particular actually get worse in terms of suspension geometry when you lower them beyond a certain point.

I've seen various setups on the forum - cars like Evolutionary's which are set super low, cars like Nils's which are set pretty low and which are level (front fender gap slightly more than at the rear), as well as guys like Warrtalon who seem to run a little higher.

Assuming you have coilovers and all the Whiteline bits (especially the roll centre kit), what works best on circuit and under what preconditions?

Also, how do people think that ride height and rake affect handling balance i.e. oversteer/understeer, noth on corner entry and corner exit?

I currently have my car set up like this - it's not slammed or anything although it's lowered - front fender clearance a little higher than the rear. Have since upped the rear ride height a bit, which seemed to make the rear want to come out more on corner exits (while under power) and more willing to come around on mid-corner (pre-apex) throttle lift than the below setup. Understeers a bit more on corner entry though.

Has a small accident recently which destroyed my big rims and 285s so I'm going back to 9 inch rims and 255 street tires (265 competition tires) and am thinking about lowering it again all around since I'll have more tire clearance but before I do that I'm curious to hear what others think.



FWIW I'm on KW V3s with 9k springs all around and all the Whiteline bushings in the catalogue.


What piqued my interest are EVOlutionary's and Nils's setups, which are possibly two of the best set up Evos around...

EVOlutionary's setup, which seems very low, especially in the rear, and which of course has won at Nationals:




Nils' setup - little bit higher but still very low at the rear vs. the front it seems (Super Lap Battle winner). Seems to be lower than EVOlutionary's car in front but not as low in the rear:



I'm not above bindly copying setups but I'd just like to know what kind of thought has gone into it.

Cheers,

 

What type of event do you want to do?

Well you took 2 of the more well known (and proven) guys on the forums - kudo's on that. You have to realize that each are setup for completely different types of events.

Evolutionary - Autocross
Nils - Road-Racing

It really depends what type of event you want to set up the car for. If it's going to be more than one type of event; you'll have to make sacrifices somewhere. On top of that, it depends what type of class you run in. For example, some autox classes (might be SM) only allow certain tire sizes like a max 245 and don't allow roll-center kits. Some road-race street events limit the tire size like Redline Street to 255. Other groups like NASA make you choose a finite amount of mods - tires being one of them - that all cost you points so you're again limited.
So, at a high level - it really depends. Oh, and I didn't even get into high vs low spring rates!

 

i have noticed that the car is planted but turns in and feels less pushy with the way Robi sets it up.
Which "seems" to have the car setup near Nils ride heights.
Would be interested to actually here the reasoning.

 

i was wondeirng about suspension also.. what is a good amount to drop for overall in terms of driving and some tracking..

 

You can go as low as you want, as long as you can cheat the laws of physics enough to get the car to still turn.

Roll center kits sound like the obvious solution, but you have to consider the nature of McPherson struts - the lower the car, the lower the roll center... the lower the roll center, the more the car is going to roll in corners... and the more the car rolls, the more the front wheels are going to pry their way to positive camber angles and reduce grip. A roll center kit counteracts this by raising the roll center, but it does not solve the whole issue.

You also want to look at spring rates. All other things being equal, you should be using stiffer springs the lower you go, as this works against the increased amount of body roll from the lower roll center. As a result, you're fixing the issues I described above - the car is rolling less, you're maintaining your camber angles better, and the car has more grip.

Getting the CG down in general (lowering the car) is important - which is why Evolutionary's and Nils' cars are as low as they are - but you also have to take into consideration the necessary steps to negate the effects of a crappy roll center, such as the case with the Evo.

In the case of "rake" (difference of front/rear ride heights), that's a whole other issue that has to do with instant centers, and I just don't know or understand the science of it enough to attempt to explain it.

 

Hmm...I do roughly a 50/50 mix of circuit work and AutoX. Under the rules I run, there's absolutely no limit in terms of allowable modifications - you're either modified or stock. I also don't care so much about comfort. The only PITA I have is clearing speed bumps and ramps if I go too low really. So I suppose the setup I'm looking for is a compromise between circuit and AutoX, perhaps slightly faouring circuit work since it's more important to me.

Not too sure about spring rates - I'm *guessing* that 9k or so, as used on the KWs, is moderately aggressive - stiffer than some of the coilovers out there but not as stiff as some of the more extreme ones (Tein Circuitmasters, HKS Hypermax 3 etc.). I've tried to go pretty stiff while still not ending up "skipping" over rouch surfaces anyways, since I do use the car on the street.

I suppose that, if the negative effect of an out-of-whack roll centre would be more roll then perhaps shamelessly copying one of the above setups and then taking some pics of the car during hard cornering on circuit would help to analyze how flat the car actually is in corners (or how bad the roll is), as well as being able to check which, if any, wheels are lifting off the ground? The possibility of terminal understeer or a second or two's worth of increase in lap times would also be a pretty good hint I suppose.

I'm a little curious to find out why Nils and EVOlutionary run so ultra-low in the rear though - to the point of scraping the fenders it looks like. Gotta be a good reason for it because I doubt they'd rub if there wasn't a good reason to do so...just very curious to hear the "science" behind it, so to speak, before I try to guess my way around it.

I've ran quite a bit of rake before (**** end in the air style) just after I got my coilovers installed and I found that I had more understeer going into corners as well as much more sudden breakaway characteristics at the back when the rear did come loose. With the car lowered in the rear to sit level (so the rocker panels are 100% parallel to the ground) it looked funny but handled much more neutral - better turn in response and less initial push, but with more push coming OUT or corners hard on the power. So I'm trying to find a good comprimise without getting all confused in an endless guessing game.

I'm sure that this has alot to do with spring rates and shock setup as well (not to mention tire pressure and alignment) but I'd rather set the ride height optimally according to some kind of logic or collective wisdom and then tweak that other stuff afterwards (bump/rebound rates, alignment, then pressure) since it's way easier. Changing the ride height over and over means a new alignment is needed each time since the toe and camber angles change etc.

I might just jump on in and try copying the big boys there but by all means keep the feedback coming!

 

Lets start with chassis rake. I come from a long family history of open wheel dirt car racing, unlike todays racers that buy everything with a credit card we built our cars from the ground up. The only suspension pieces not made by hand were the shocks and the rod ends. The advantage was that we already knew the technical details of our chassis so it made ride height and those type of things much, much easier to deal with. The Evo was an unknown for us so like everyone else we just had to start somewhere and work with it.

Most the posts I see involving rake are attempts to improve cornering and while it will have an impact on cornering, chassis rake is really there to help you go straight! Since the Evo was set-up for the average Joe on the street it has a bunch of chassis rake. Like the inherant understeer, this is good for an average person, but not a race car driver.

Now of course we only had to go left, but its not as easy as it looks! For a winged midget on a short track, 1/8 mile or less, no rake. For a quater mile oval increase the rake to 1/4", for a one mile track, increase to 1/2". The reason we did this was because of our tire stagger, but even at that, doesn't take much to make a differance.

No long straights in autox, your almost always in some form of transition, I would start with 0 rake and if anything, lower the rear of the car, maybe up to a 1/2" or more. For a road course I would start at 1/2". If I was at a track with long straights that would be O.K. but if I was at a track that was mostly curves and short straights I would again lower the rear at least another 1/4".

For ride height I measure the bottom of the pinch seam weld just ahead and just behind the jack points. Right now I'm 6" in front, 7" in the rear, this gives me about 1 deg of rake which works well on the street. For tracking the car next year I'll take another 1/2" out of rear and start with 1/2 a deg of rake.

Only ballpark figures, but a place to start.

 

i dont know the exact science behind it..... lower is always better to a certain point.

most guys out there lower their cars too much infront... neglecting all that weight that sits on the front axle & their suspension travel... and most of them dont even have a roll center kit installed either.

 

You also have to look at the camber curve of the suspension. The camber curve for strut based front suspensions blow....

Basically, if you lower too much, it puts the suspension setup in the 'bad' part of the curve. This is where when the suspension compresses, the camber goes positive!

My advice would be to not lower too much from the factory height. The OEM engineers take all that stuff into account.

With race cars with strut suspensions that are really lowered, sometimes what they'll do is just make the suspension so freakin stiff, that the suspension barely compresses and therefore the camber doesn't get effected too much.

 

I don’t know if I learned any science but the on the job training was sure fun! But your right, there is always a limit, only so much usable range for any given design. Ours is a 2003 chassis so we’re adding the roll center kit as part of our track preparations. After the holidays we’re going to change the front sway bar and add the roll center and steering kits while the sub frame is down.

 

I decided to try a little on-the-job training myself on this one

Have lowered the rear substantially just for the heck of it. Bottom of the rocker panels are about100% horizontal to the ground right now and the car is quite low overall. I think I'll take it even further this evening and do a little testing in a parking lot somewhere just to check it out more.

So far my impression is that the car turns in just as well as before and feels more stable overall - less like it wants to "bite". The rear end can still be easily coaxed out when deliberately provoked (i.e. trailbraking, sudden lift) but the breakaway seems much more pregressive than with the rear set up high in the air (i.e. positive rake)...much much more controllable this way.

Seems to want to push more in the last third of the corner on exit but more controllable under heavy throttle. Although I can't seem to put the power on much earlier on exit I find I can put more power down more confidently when I can see through the corner exit, with less twitching/fishtailing/countersteering etc.

FWIW, I'm running what I think is a pretty well reasoned setup: -3.2 camber front, -1.3 camber rear, 0 toe front, 0 toe in rear. KW V3s - Front shocks 1 turn from full stiff, rear 0.75 turns from full stiff with 1.25 turns rebound from full stiff, 1 turn from full stiff rebound in the rear. 9k springs all around.

I like to run 0 toe all around if possible in order to wear on the tires less, and also to let the suspension do the work as opposed to relying too much on extreme alignments.

Works for me anyways - perfectly neutral handling, car can be rotated at will but doesn't bite, no push, no snap, just nice 4 wheel drifts if I'm driving a little over the limit.

Just throwing that out there anyways

 

Ha, that’s funny, I did the same thing last week, only I went the other way. I raised the car ½” and went back to a previous alignment set-up, the car actually feels better. Height at the bottom of the weld seam is now 6 ½” front, 7 ½” at the rear. I still want to lower the rear ½“, but I wanted to go back to a known set-up first and hopefully minimize the impact of lacking the roll center modification.

 

You never know...in the quest for perfect handling I've tried ALOT of stuff. It's a never ending thing...pretty pleased as punch with the setup now though.

I measured according to your method of using the chassis seam under the car...runing 6.5 inches front clearance, 7 rear. Seems to work nice

 

^ now that's a good looking car.

(from a looks perspective, I think it looks like you have a load of bricks in the trunk -- personally I run front rake because I like the look, but I *know* it is hurting my performance).

 

Don't "know" till you try...I believe in experimentation! Who knows...I might raise it waaaay up in another few months

Thanks for the compliment - I try to make her purty but she's got more than it's fair shair of blemishes in person unfortunately. Hard life.