Tire Spin During Autocross

[bmw-autocrosser]

I run an '01 325i about twice a month in Autocross events. I am pretty competitive but having one problem I can't resolve. Rear wheel spin is pretty bad, especially coming out of the corners. I am running koni sports on all four corners and Kumo Victo Racers (225/45 - 17s). DSC is turned all the way off. It got better with the new shocks, but still a problem. I usually run the tire pressure in the rear around 37-38 PSI.

Anyone have any ideas how to make it stick a little better and still keep me in stock class that would be great!

 

[Big Daddy]

I am not sure if the 01 325i came with one or not, but a rear sway bar would improve traction assuming that you do not have one now!

 

[Kirby]

There's nothing else you can change on the car and remain in stock class. Changing the sway bars will bump your class.

There's a saying in racing that you can't fix the car if you can't fix the driver. The primary problem is that the driver needs to be fixed. You need to not to get on the gas pedal so hard coming out of corners, and maybe change your line so that you have less weight transfer off of the inside rear wheel. Of course, I know this is easier said than done.

The gut instinct is to mash the pedal to accelerate out of the corner. The problem is that you upset the car's balance, heat the tires, and loose time. The smoke and squeal looks fast, but you are loosing .1 - .25 secs each time you do this.

If you watch the best drivers closely, you will notice that their wheel spin is minimal. If you REALLY want your eyes opened, ask one of them to run your car in a fun run.

The cheapest and easiest solution is to buy this book, read it, read it again, and repeat about 7 times. It will be the BEST investment in Autocross you ever make, the $15 is worth more than $1000 of car mods. I know from experience.

www.speedsecrets.com

 

[epj3]

LIMITED SLIP! But kirby is right because autox IS all about driver control.

 

[bmw-autocrosser]

Thanks for the response. Yes, you are most correct, it is very hard to get back on the throttle easy, I typically end up mashing the throttle and then having to back off to get it from spinning.

 

[bmw-autocrosser]

There's nothing else you can change on the car and remain in stock class. Changing the sway bars will bump your class.

Actually you can do pretty much anything with the front sway bar, but can't touch the rear to stay in stock, at least in SCCA. I don't know about NASA. Reference: 2006 Solo Rulebook, Pg. 65 Sec 13.7

 

[epj3]

There's nothing else you can change on the car and remain in stock class. Changing the sway bars will bump your class.

Actually you can do pretty much anything with the front sway bar, but can't touch the rear to stay in stock, at least in SCCA. I don't know about NASA. Reference: 2006 Solo Rulebook, Pg. 65 Sec 13.7

But changing the front sways really only help reduce body lean/sway - the rears can actually determine over and understeer.

 

[Kirby]

There's nothing else you can change on the car and remain in stock class. Changing the sway bars will bump your class.

Actually you can do pretty much anything with the front sway bar, but can't touch the rear to stay in stock, at least in SCCA. I don't know about NASA. Reference: 2006 Solo Rulebook, Pg. 65 Sec 13.7

Yup, I agree, that's why I said bars. You would have to change the rear to work on wheel spin, and with a stiffer rear bar, you would want to change the front as well.

 

[epj3]

Yup, I agree, that's why I said bars. You would have to change the rear to work on wheel spin, and with a stiffer rear bar, you would want to change the front as well.

Bought the book you reccomended, it's a pretty good read so far.

 

[bmw-autocrosser]

Another good book is Secrets of Solo Racing by Henry A. Watts.

Concur with the rear sway bar, but my goal is to try and stay in Stock Class. If I move out of there I am afraid I will get out of control on the upgrades (read $$$$). Wife is tolerant so far....

So with that being said, I am considering an upgrade to an adjustable front swaybar. Good idea, bad idea without also considering the rear?

 

[nadroj]

maybe go with a little less psi in the rear?