I want to reduce understeer. Some say that the front tire pressure should be raised and some say it should be lowered. I would really appreciate advice from someone who knows from exprience.

 

Lowered. To reduce understeer

Generally:
Stiffen the front- the front hits the wall - under-steer
Stiffen the rear- the rear hist the wall - over-steer

 

I think the tires you are using are the big problem. I have had two different sets of tires, both summer compound and very sticky, and it is still there...tried lowering, and inflating...the car needs some suspension work, which I don't care to do, since I'm a straight liner....the guys going round and round will chime in...but, having a great tire can't hurt...

 

Thanks Arejohn, I interpret you answer to mean that to decrease the understeer I lower the front tire pressure.Then I could also raise the rear tire pressure but if that makes them stick less thats a negative. What do you think?

 

You want to try to move weight to the rear. So lower the pressure in the rear and raise the pressure in the front. Or better yet, change out the spring pads in the rear for the thinnest. It will help some but don't expect a miracle.

Les

 

What tires are you using? Is your car a base Crossfire or an SRT-6? Tire pressure is not the best way to compensate for suspension calibration.

I'm running a new set of Dunlop SP Sport Maxx TT's at OEM sizes with OEM alignment specs and manufacturer recommended 36 PSI on an SRT-6. I don't have a lot of understeer. The SRT-6 corners flat without tire squeal and very little push. Any understeer is very controllable with trailing throttle oversteer or throttle or steering. I like the setup. Just enough understeer at the limit to make the car easily controllable. And grip levels are pretty damned high. I actually worry more about the opposite problem. The car can be a bit tail happy with this much low end torque in a 3,200 lb car.

Other good street tires...Continental Extreme Contact DW's, Bridgestone RE-11's.

 

Weight to the rear would. That's why you STIFFEN the rear. During a turn weight shifts to the outside wheels. More weight will be on the stiffer end.

 

Try more air in the front and less in the rear. Just try it. If it makes it worse then do the opposite and call me wrong. I'm assuming your pushing the front entering the turn and not in the middle or coming out of the turn. My car likes more pressure in the front, (39 to 42 lbs. hot) as much negative camber possible and a little toe out. Toe out is bad, bad, bad for the street but great on the track. The truth is that I've changed so many things that I can't remember what worked best with stock suspension and tire sizes. Good luck.

Les

 

Mine is the bassic CF. 2004. The rear tires are the stock Contis. I just replaced the fronts with the very sticky Dunlop Z1 starspeck. Please, no sermons on different front and rears. I bought the new stickies, of course, to reduce understeer. I'm sure it will, but if it still understeers excessively I can experiment with F@R pressures and the camber bolts(which I have).
I was affraid of getting conflicting views on the pressures but it was worth a try. Thanks for the replies.

 

Yeah, well here comes the sermon. The Star Specs are an excellent tire. I had a set on my S2000 for a year and loved them on dry roads and in the rain. But, you've just mixed a very sticky extreme performance tire with a long wearing set of all season Conti's that are 6 years old. Nothing good will come of this. Why are you farting around with tire pressure and mixing tires? Why not just put a proper set of tires on the thing and then work through suspension setup until you dial in the behavior you want?

 

Hello Spudracer, my question was whether raising or lowering the front tire pressure would reduce understeer. Instead of giving me an unwanted sermon on tire use you could have just answered my question with "I DON'T KNOW".

 

Well, that wouldn't have been an honest answer because I do know. It won't make a substantial difference. It certainly wont give you what you're looking for. And mixing tires on the cheap won't compensate for suspension geometry and components either. Don't you think that if crap solutions like you're espousing worked everybody including manufacturers would be doing it? I was just trying to save you some time and money and possibly keep you from compromising the safe handling characteristics of your car. But hey, it's obvious you'd rather believe in the $9.95 fix. Enjoy! But please don't ever come near me on a track.

 

Still more useless rhetoric that doesn't address my question. Thanks for nothing. Your'e a real credit to this forum.

 

All I can tell you is how I learned. After my first time on the track I felt like you do. Fix the car, make it better, change things etc. I put a pulley, CAI, shocks, brake pads etc. and my times stayed the same. I put Eibachs on the car and went slower. I put camber bolts, adjustable camber arms in the back and wore out my stock tires by 2000 miles. Bought the stickiest street tires I could. Michelin Pilot Sport Cups (80 treadware) I was still within a second of when the car was bone stock. Went to a driving school and gained more time than all the "improvements". Now I'm on street tires again, I've learned how to drive the car when it's loose, when it's tight, with fading brakes, in the wet etc. I can have the car set up perfect for one track and at the next it isn't. Track surface, temperature and other factors change how the car behaves. Until I practiced different braking techniques, early and late turn in, using the throttle to turn the car and other techniques, I didn't understand how to take advantage of what the car did well. If you think your Crossfire has problems pushing try a FWD car. Having been through it, being stubborn, not believing it until learning first hand, being impatient. I understand. You have the new rubber for the front. Use them and see what is different. Your going to have to learn to get the most out of the grip the car has no matter what tires you have. Try different pressures to see what changes. In the end what will have to change is your driving style. You won't be successful adapting the car to your style. In the end, in any car, you have to adapt to the car strengths and weaknesses. Learning and trusting internet opinions isn't always easy, but often right on the money too. It's best to go to a driving school if you can and see first hand what is possible. The instructor will drive your car and usually give you several epiphanies. Good luck, don't blame the car, learn what it can do and can't and have fun.

Les

 

Thanks much Veloci, Your reply clearly is based on experience and deeply appreciated. The basic CF has unbelievable understeer. My next track day is on May17th. I'm hopifull that my new stickies on the front will reduce the understeer enough that I can learn to adapt to the car as you suggested. If the understeer is still rediculous I still have the camber adjustment bolts. Your suggestion about driving school was good. It's hard to tryout new driving techniques on the track. I'll let you know how much the stickies helped (if any). LOL

 

Yesterday was track day and I'm as happy with my Dunlop Z1 starspecs on front as I can possibly be. I won't say how much it improved my track time because its unbelievable. But I would encourage anyone with a standard CF with factory tires to buy these Dunlops for the front.
I'm disapointed with MB for making such an otherwise wonderful car that understeers so badly. But I'm glad I found the solution. It was like driving a different car. I spent most of my track time learning to drive it. But it was fun. I started out with an additional 3 more lbs in the front tires and just left it there. When everything's right don't fool with it. Thanks again guys for all the help.

 

I'm glad it worked out favorably for you. When those rear Conti's are done, get some matching Dunlops for the rear. The Conti's are for comfort and really don't grip all that well.

Les

 

Wow! That was a quick reply. Thanks Les. I wanted to buy 4 this time but they don't come in 19 in.
I may never wear them out anyway. I don't drive it that much. The car has 20000 miles on it and the tires still look good.

 

You have to get to the track more often! My car has 8640 miles and I'm on my 5th set of tires. Stock Michelins, 2 sets of Pilot Sport Cups, 1 1/2 sets of Yokahama Advan Neova AD08 and now I'm on Kumho XS.

Les

 

A little off topic for this thread, but didn't want to start another one. Might be other threads better suited for my feedback, but this one will do.

Checked all my tires on the various cars in our stable this week. Found nearly all the tires about 2-3 psig lower than I typically run. Most likely due to the decreased temperature occuring right now.

Anyway, inflated all the tires to proper air pressure and good-to-go for another couple of months. (Note: I usually check the tire pressures every 8-10 weeks.)