automobiliben

So I participated in my first Auto-X this weekend, what a blast! I was actually impressed with my driving, I ran consistently within 1/10th of a second of my time in 3 runs, too bad there weren't any other cars in my class to compare my times to. I was running 40 psi (stock tires) on all four corners and my car handled really well through the chicanes and the chicago box. But there was a long sweeping 180, moderate speed, and my car had a tended to push (understeer) through the whole turn. What should I do to improve my handling? BTW, I am not really looking to buy new tires yet and would like to keep my car in the stock category.Thanks.

alleycat58

Tire pressure, tire pressure, tire pressure.

If you want the front to stick and the rear to step around, lower the front pressure. On an SS/SC with stock tires, I'd run 44 rear, 39 front. In my Tech-R's I run like 48 rear, 43 fronts.

To start with, try 40 in the front, 42 in the rear. Or 42 in the front, 44 in the rear. Then adjust as you go. But start with the max pressure you want to run i the rears, it's always easier to bleed out pressure than keep inflating them till you get where you want.

Cman06sssc

GM Power. I shoulda got a frikin bimmer. I hope you figure out the correct pressure to run on those stockers for the auto X. Good luck.

mikey80z

I too ran my Cobalt in it's first autocross this weekend and was impressed with it's handling. Everyone it talked to there said the same thing about tire pressure. I noticed that i tore up the sidewalls pretty good indicating a need for more tire pressure. I did have fun however taking out cars that are 10 to 15 thousand dollars more than mine.

skoshi130

When I ran my TT(auto-x) I had 40psi for front and rear on stock and the sidewalls came out ok

Sicklyscott

iTrader: (1)

I also have to say though, some novice (and no offense to the original poster) believe their car pushes but in actuality, you're just exceding the limits of the car/tires. The SS S/C is balanced very well and unless mid turn flooring it, I haven't really noticed the car pushing anymore than expected with a powerful fwd arrangement.

Now to add something constructive, tire preasure is huge. You can definately compensate for "bad" handling characteristics as stated above. I used to run 40 psi up front and 42 in the rear on my GTI. It worked great and really allowed the car to rotate on its axis.

Also try and remember, in order to go faster, drive slower. It really works, especially while learning to auto-x.

Its addictive, have fun!

automobiliben

Yeah, I noticed that my sidewalls are starting to wear a bit, not a lot but noticeable. I started with 40 (front) /42 (rear) and then dropped it to 40/40. I take it that I went in the wrong direction. I was trying to make the rear a little loose, but no luck. I guess I need to get a portable pump. What about a sway bar, I could put on a front one and stay in the stock class?

automobiliben

Yeah, I made sure to start slow and work my way faster and faster. I made sure to work on modulating the throttle, I think a psi change could fix it.

SoloZ/SS

Very true, slow in fast out. http://www.ykwmotorsports.com/Images...eos/cobalt.wmv stock tires can be good for autocrossing but it just takes a fine adjustment of the pressure and to not overdrive the tires, heck they can't do everything. I have actually enjoyed driving my car on the stock tires(not having to change to R compounds is great) and being competitive is part of the fun.

Sicklyscott

iTrader: (1)

If you want the rear to "rotate" then you want to have higher tire preasure in the back. What I would do in the case of tire preasure is to mark the front tires with chalk and do my first run with 40 psi in front and 42 in the rear. I'd see how the front faired by checking to see where the chalk has rubbed off. The reason why I would initially pay more attention to the front is because once you get it all situated you'll be getting maxiumum grip from those tires.

After the front is all compelte and tuned in with tire preasures etc, I'd then proceed to put air in the back tires until you get that rotating feeling where you take a corner and the back end just steps out a little bit. Remember, you want to keep this controllable. One way of getting this movement is by trail braking which adds more weight to the frotn tires therefore less on the rear which will help the car rotate.

If your car "pushes" the worst thing you can do is add a front sway. However, just to pointt his out, our cars already have a front sway stock. If the tire preasure thing doesn't work out or you're finding that you auto-x a lot and would love to be a bit more competitive, go find yourself a REAR sway bar, I've heard great things about the progress rear sway but it will probably take you out of stock class.

Hope all this helps!
Scott

automobiliben

Thanks for the help. Yeah, a rear sway wouldn't be legal. The biggest problem with Saturday was that it was just for fun, there weren't any classes and it was just a learning experience. After each run we just go back in line to do more runs, it didn't allow for much time to mess around with air pressure. How do you trail brake? Thanks for all the helps.

suburbanrobot

glad you had fun...where did you run?
here is an upcoming high speed AUTO-X... i'm going to this one!
https://www.cobaltss.net/forums/autocross-road-racing-53/high-speed-auto-x-10-15-lake-geneva-raceway-33222/

automobiliben

Yeah, I have seen that one, I wish I could go but I got some family stuff going on that weekend. I ran here in Peoria, it was put on by the Porsche Club of America.

automobiliben

Is anyone that has posted in here interested in getting some wheels for Auto-X, it would be a group buy through Rota, we need 5 people. I posted up a thread already but it seemed like interest was very sparse. At 17 lbs. a piece we could loose 30 lbs off the car over stock...

suburbanrobot

thanks for the offer... but I am already out of stock class.... so i bought some ASA 17" x 7.5" rims @ 20lbs each, w/ dual purpose in mind > snows in the winter.... i'll put stickies on those for auto-xing next spring so as not to trash my street tires.

also there is an event at AUTOBAHN in October as well! I know I posted that somewhere, check my threads if you are interested

stay in touch and we'll eventually do an event together!

automobiliben

Sounds good, I am in the process of trying to get transferred up to Aurora, so the possibilites of that are very high.

Sicklyscott

iTrader: (1)

Trail braking is basically staying on the brakes until about 2/3 of the way through it. What it does is put the weight on the front tires giving them more grip. It's a very hard technique to do while thinking about it and purposely trying to do it but once you start finding the best lines for you and your car, you'll notice that it comes a lot easier and more natural. It will allow you to brake later, be a bit slower int he turn but be able to set you up for WOT out of the turn.

This is a decent read, although it will make your cross-eyed
http://www.getfaster.com/Techtips/Physics23.html

and this one is pretty good too
http://virtualracersedge.com/trail_braking.htm

SoloZ/SS

You can allways try the lower rear pressure method, instead of using a whole bunch of pressure you use maybe 30 or so maybe even less(I haven't tried it this way) and it makes the back end more controllable but it can still come around. The high pressure rear method can make the rear end snap out making it a little difficult to handle.

suburbanrobot

yes SoloZ.... I also opt for running lower pressure in the rears...I feel higher pressure in the rear makes the sidewalls too firm, it rides too hard on rough AUTO-X surfaces and makes you bounce over the road imperfections...instead of the tread staying planted on the pavement

Sicklyscott

iTrader: (1)

I've never tried the low preasure method, sounds interestnig. I'd like to eventually be able to mark all tires with chalk and get the porper roll-over and then just adjust it witht he suspension but that requires a lot of work plus externally adjustable rear shocks which I haven't been able to find.