OK, so I went from 255/40 front and 275/40 rear to 275/35 on all corners (18" wheels). I have RSR springs, Koni yellows (med. setting) and Stillen sways (med. setting). My new tire/wheel setup has eliminated the understeer but now the rear doesn't feel as planted on high speed banks. My gut feeling is that I need to lower and soften the rear spring rate but I really know little about adjusting suspensions for fast cornering. So my question for the suspension gurus is this idea whack or not? I'm considering running the Tanabe GF springs in the rear while leaving the RSRs up front - Bad idea? If my numbers are correct, I would have 345 lbs/in front and 375 lbs/in rear with .6" front and 1.2" rear drop. Currents are 345/.6 front and 417/.6 rear. Thanks for your help.

 

Hey Brian,

It sounds like a lot of what you are describing is due mainly to your going to the same tires all around and now the handling characteristics have changed. Softer springs will help the car hook up out of a corner, but may make the car feel more "floaty" at high cornering speeds (this is somewhat subjective). Suspension tuning is largely a matter of feel. But what you are describing is not "whack." Sometimes you need to play around with spring rates to get what feels best, so running different springs front and rear is fine - the trick is getting the car to feel balanced in the corner. What you are describing is certainly worth a try. I have played around a bit with the spring rates on my coilovers as well. What you are describing sounds like it will serve to equal out somewhat the spring rate front to rear, which might be a good thing, given that the weight distribution of the car is not far from 50/50. In fact, many people think that the car is better balanced with heavier front springs than rear springs. (Most coilovers are sold with either equal rate front and rear springs or heavier front springs).

 

Might want to try playing with your shock and sway bar settings first. Stiffen up the front, see what happens. Tuning the spring rate may be preferable, but if you can fix things with what you've got already, why not?

 

And of course, the easiest and simplest thing to try is adjusting tire pressures! You would be amazed, but you can actually feel if you are off even one pound of air pressure. Are you running same pressures all around? My experience is that if you run a few pounds more in the front than the rear on a rear drive, front engine care (one that is heavier in front than in the rear) that is usually optimal. What pressures are you running? Every track may have different optimum settings, and settings for the track are different from auto-x, etc. At PIR, there are more left turns than right turns, and maybe you want pressures staggered side to side as well. Also, different brands of tires have different sidewall stiffness, different grip levels and may have different optimal pressure settings.

 

Thanks for the ideas. I'm currently running 32psi/30psi f/r per Falken's recommendations.

Steve, would you concur with stiffening the front sway? I don't think I'll get much out of the Koni's as I can only adjust rebound.

 

Hey Brian, Happy New Year!

I don't recall which sway bars that you have (Hotchkis like mine?). What are your sway bars are set at now? I run full stiff front, middle setting rear, and that has worked best for me. Stiffening up the front should make the car feel more stable at speed. Hopefully, that won't bring back your understeer (but it didn't for me, and I am running same size tires at all four corners like you). I am surprised that your tire pressures are that low. I thought Falken was recommending slightly higher pressures (per their website). I ran 35 psi front, 34 psi rear in my Falken RT-615s at the Spring Mountain Redline Time Attack and it felt quite good (although I admit I am still experimenting and want to try a little less). If I were you, I might try bumping up 2 psi front and rear from your current settings to start. I know that the RT-615 sidewalls are stiff, but a little stiffer than 30 psi might help reduce the squirrely feel.

I am surprised that the Koni's only adjust rebound. I thought they adjusted compression and rebound at the same time (like my Tokicos). Hmmm... learn something every day!