This question has probably been asked before, so I apologize in advance.

I am pretty new to autocrossing (only 3 events) and am finding out quickly it's going to be expensive, considering the tire wear.

I was wondering if I could be competitive, and if there would be any front clearance issues, if I ran:

kumho ecsta mx's - 245's front and rear on the STOCK rims (17x7 and 17x8.5)

This is so I could rotate them instead of just trashing the rears. I noticed the national competitors are running 245/275 on r compounds with agressive alignments, but are they just putting up with front rubbing, or is there not any??? I am currently running .8 neg camber in the front and 2.0 in the rear.

Thanks for the help.

 

Someone who actually races an S2000 will correct me if I'm wrong, but I believe there are two things you will need to do to make that work.

* Set your front camber to its maximum negative setting to prevent rubbing
* Install a stiffer front sway bar to bring the handling balance back (with 245s all around on an otherwise stock car it's going to be very loose)

 

you can run 275's without any rubbing issues but I would max out the front and rear for negative camber, at Nationals this year I ran 285-30-18 front and 295-30-18 rear on 18 X 9 OZ ultraleggaras in BSP with out any issues.

Jason
6th place BSP 2006 SCCA Nationals

 

There are three issues with your plan.

First of all, you physically can not rotate the stock wheels front to back. The rear wheels have a smaller center bore so that they won't fit on the front axles.

Second, handling balance. I am running 245/40-17 tires all around. However, several factors allow me to do that:
1)I have a super-stiff front swaybar, set at its very stiffest setting. That trades off front end grip to get more rear end grip.
2)The tires are R-compound tires, which means that they have much greater traction than regular street tires. They have enough grip that even at full throttle they have significant reserve grip for cornering.
3)I specifically wanted to shift the handling towards oversteer. I have the experience and the smooth driving style to keep the rear of the car in line.

Third, rubbing. 245/40-17 on a stock wheel will rub the outer edge of the front fender if you corner hard enough and/or hit a big enough bump. 245/45-17 will rub even more easily. I was actually unlucky enough to have a street tire with tread catch on one of the metal tabs that holds the front fender liner. That was a 225/45-17 tire after hitting a dip while cornering. It was bad news for both the tire and the fender. I think that rubbing with a street tire can actually be much worse than rubbing with a smooth surfaced tire, because the blocks on the street tire can catch on edges and grab. 275/40-17 V710 will not rub on the rear. The reasons that people are able to run the 285/30-18 on the front of BSP cars without rubbing is that it's not only a smaller diameter tire, but BSP cars have stiffer suspensions which don't compress as much when cornering or braking.

PS - autocrossing should wear the front and rear tires fairly evenly on the S2000, if not a bit faster on the front. It's street driving that will trash the rear tires faster than the front.

 

just run 1000 lb front springs and a gendron solid front bar, it rides great!!!!!

Jason
REALSPEED

 

Thanks for all the input.

I noticed that-my fronts are now equally as trashed as the rears after yesterday's autocross event. (I need to tone it down on the streets, too)

This is what has happened.

First autocross: rear tires pretty bald going in. Car felt horrible (like on ice) One tire actually shredded on the course, and I drive home on spare. Way behind others in times.

Second autocross: fresh rears, fronts still good. Felt great and finished very close to others.

Third autocross: both front and rears are near bald going in-rears worse than fronts-car feels slippery but more neutral than first autocross-fairly bad times again.

Now my car looks like it's on r-compounds all the way around. Time for new tires.

What if I bought 235's for front and rear to drive on street 'til February, and then switched the front and rears after adding a front swaybar for the next autocross? Would the 235's stretch over the the 8.5 width rims in the back? Just trying to find a way to be competitive for 2 autocrosses in a row before having to purchase tires.

Thanks again for the input. Love the detail, orthonormal.

 

At this point, you are probably going to tell me I need autocross tires AND street tires. BTW, what does mounting/unmounting usually cost?

Ideally, I buy used rims and just switch these out, but it will be a while before I can afford those.

Thanks for the help

 

For mount & balance, I've seen charges as high as $30/tire, and as low as $10/tire.

I don't think that you necessarily need two sets of tires. I ran Falken Azenis for street and autocross on my Miata for about 6 months before I switched cars, and I thought it worked out great.

It sounds like you were wearing the tires a lot in between each of those autocrosses. A set of "max performance" tires (Tire Rack's category) should last you from 6 months to a year of fairly intensive autocrossing and moderate street use. They should definitely last for more than two autocrosses unless those autocrosses are more than 10,000 miles apart, or involve more than 40 runs each...

How about getting a set of the Kumho ECSTA MX or Hankook Z212 RS-2 in the stock sizes (215/45-17 and 245/40-17)? Either is a little over $400 for a set, which really is cheap for performance tires in our sizes. Or perhaps the Falken Azenis RT-615 in 215/45-17 and 255/40-17 for a bit more.

Having a suitable alignment and running suitable tire pressures can have a large effect on tire wear. Have you done anything about either of those?

 

I like the idea of the Falken Azenis RT-615. Haven't tried those yet. Any particular reason you recommend the 255 on the rear for those tires and not the others? Do they not make a suitable 245?

On alignment and tire pressures:

I run 32 (checked cold) all the way around (although I'm finding my presssure gauge is acting funny-I'm going to get a good digital, I think)


For alignment, I had been running .7 neg camber in front and 1.7 neg camber in the rear. However, I inched that up just a little to .8 front and 2.0 rear just before the last autocross. I definitely need help in this department-what is a good dual purpose alignment (for street and track)? Should I just leave it stock? I definitely wear the middle and insides down before the outside edges on the streets, but was afraid the stock alignment would kill my potential for top times on the autocross. (I know it's driver-that's why I said potential )

 

whats your toe settings? as i understand it, more rear toe in is more important for auto-x...