Hey guys....I've been trying to get my car ready for the season this year and have encountered a slight problem. During turns is feels like the rear end of my car is a total seperate entity from the front. It feels like the rear end is rebounding too much, springing up, then trying to over rotate.

I was just curious if anyone knew how to correct this at all. I have the RRE tune JIC coilovers set to their specs. I have changed tires to the Kuhmo MX tires since i couldnt afford to spend 1000 bucks for factory tires. Nothing has a sidewall as stiff as the yokohamas....but i still need some help dialing this irradict behavior out of the car.

Thanks for the help in advance!

 

I personally found the Kumhos unacceptable for track work as they are far too wobbly. If you are trying dial out the wobbles caused by the Kumhos it won't work. You might try an alternative tire like Falken Azenis RT-615, or something else with a stiff sidewall. Also, how did you set the toe and camber on your JIC setup? If you haven't gotten a proper alignment, your tires are probably toed way out. Too much rear toe-out will cause your rear end to swing around too much, along with excessive tire wear on the insided.

As for the bounciness, usually it means your springs are overpowering your shocks. Without experience with coilovers I don't have definitive advice, but I would consider the RRE settings a great starting point, but of course it's not going to be perfect for everyone every time. There are too many variables. I would play with the rebound and dampening of the rear myself, and it sounds like you need a little more of each IMHO. Good Luck!

 

I agree, get an alignment if you haven't already had one. Lowering the car with coilovers will change camber, and more importantly, toe. I've had drastic rear toe out on my car after installing coilovers, and it felt like the car was all over the place.

 

several things on top of what has been said. what's the tire pressures all the way around and when are you experiencing this type of problem? after warm up or before? stone cold tires always seem to kick the rear out more readily even in a neutral setup like the jics.

also is the rear actually coming up or are you getting oversteer catch oversteer catch type of feeling because that would be due to the sidewall slop. you can try more camber in the rear to alleviate that but i don't think anything replaces a good tire. and if you're skimping on tires i don't think you should compete in anything.

also what profile tire are you running? tire selection is very important if you're going to go for a known softer sidewall tire you can at least get a smaller profile and a wider tread patch.

 

I have a -2.0 degree all the way around and a 1/16th inch toe in by the recommendations on RRE. I have a feeling it mostly has to do with the tires. I think I might have made it sound worse than it really is. Personally I like the stock yokohamas better, but these tires really aren't bad at all....turn in is still nearly as quick, and sticks really well. I guess we'll just see what happens at the autocross. If they suck i'll just burn them off as fast as I can and get some Toyo RA-1's or something. I'd buy stock tires, but I just can't be shelling out 1000 bucks on tires every year. I'm a poor college student!

Tire pressures I believe are aroudn 38 all the way around. Thats what they were set at from Tire Rack.

As far as the type of oversteer I'm getting its only on certain types of uneven road during fast sweeping turns. It hits the bump...kicks alittle then starts regaining composure. Its just the kick part that can get someones attention pretty quick. This kick was really bad with my winter tires....which leads me to believe that its mostly sidewall stiffness related.

Kuhmos would not be my first choice obviously, but my dad helped me out because he knew I needed new tires immediately and had no money. So he suprised me with them. Just trying to get the most out of them that I can for now.

Also thanks for the help and advice!

 

oh yeah i;m running 235-45-17 on a 17X9 wheel

 

ah gottit. this is what's happening. you're running a stretched tire which gives you a semblence of more sidewall stiffness and also comes with a twitchy handling characteristic.

what's probably happening is when you hit a bump and it unsettles your grip it's breaking away suddenly becauase of the very squared shouldering from being stretched and then there's a delay when it hooks back up again cuz your pretendingly more stiff sidewalls really actually buckle under the jolting. prolly scoots real fast then has a gradual regrab on the pavement.

 

If you're a poor college student, RA1's will be the last tire you want to buy.

 

If sidewall flex is you issue, ra1s wont solve that. While they are fantastic track tires, they have a much softer sidewall than say an a032r. My recomendation is give the advan a032rs a try. i had them before and personally i love them for their predictability and sidewall rigidity. Plus they are super cheap now on tirerack and most tire sites. just my 2 cents.

I was just going over your post, and you mentioned that you have -2 degrees all the way around. Im nto sure if thats the way to go. I have 3 degrees up front with 1 degree in the rear dialed into my ohlins and i couldnt eb any happier. Id try taking out soem cambe rin the back and adding some to the front.

 

yeah i might try to take some camber out of the rear....i was supposed to put 1.5 in the rear, but for some reason the people had difficulties getting anything less than 2 deg. The car is extremely low, but I trust RRE and couldn;t be happier with the setup. Just trying to work with the tire alittle bit i guess.


Thanks again for the continued advice!