16X10 or 15X10s?
 

I have read the wheel filiment thread and a few others....

I am looking for opinions on wheels set up for Scca F-Prepared Auto-x. The car is a prepared 91 2nd gen with EP flares. The rules allow tires to extend beyond the wheel wells.

I know most of the usual arguements...Looking for comments from those who are running specific size wheel combos.

I am considering 15 or 16 X 10 wheels. Which tire and wheel combo are you using? 16x seem to offer a few more choices in tire compound

In general, it appears for 15X10 the backspace is about 5".
What would be the backspace for 16 X 10s?

What is the hub size?

Thanks

Backspacing would probably be the same for both wheels, since they are the same width.
Most FPrepared cars I've seen run the Hoosier 22x10-16, but that leaves you very little sidewall. I'm considering running a 15x10 wheel and running the 22.5 X 9.5-15. This will give an inch more sidewall and might make the car a little more forgiving at the limit. It's also available in an R25 compound, but that's probably way too soft for even the lightest of FP cars. I've never driven the 15" combo, so it will be kind of an expensive experiment if it doesn't work. But that's racing I guess. :)

That 22.5x9.5-15 tire is made for the front of a Formula Atlantic car, which probably carries at most 250 pounds weight on each front tire; probably closer to 200 pounds. Your car is probably too heavy for that tire.

I have been road racing with 15 x 10 wheels with the Goodyear 23 x 10.5 x 15 tire for several years now, and I really like how it feels. Actual outside diameter is closer to 22.7" Unfortunately the selection of 15" low diameter slicks is getting smaller and smaller, I just ordered the last of the 23x10.5x15 tires available, and Goodyear says they won't make more until they receive an order for more. I may have to go to 16's if I can't find any more decent 15" tires. I cannot afford the expensive Avons.

Unless you have a big tire budget (not comon in Solo,) you may want to consider the more popular 16" size just so that you can easily obtain used slicks.

Since this is for a prepared auto-x only car, I try and avoid harder road race compounds. They do not come up to temp fast enough to be for full benefit on the typical 45-60 sec auto course. I am leaning towards 16X10s at this point. Would the back space 5" ? I am probably going with circle or bogart wheels.

Thanks

Russ, 16x12 rear 6" backspace with a hoosier 23.5-11.5-16, and a 16x11 with a 6" backspace, and a 1/2" spacer up front(since circle is 1" increments), same tire, or an 11" tire. I run those wheels with Goodyear 24.5-13-16 rear, and 24.5-11.5-16 front, but as mentioned above they are a road race compound, and are not optimal for AX. AVON does make the exact sizes, and compounds for perfect fitment, and compound, but they would be special order from RKR. Alternately, you can use a modified strut, and use a 16x12 up front as i told you in our Hour long conversation ;) Maybe I'll just right a book....Carl

Our conversation was very helpful. I appreciated your time. I am not sure if I want to pay a weight penalty for 16 X 12s. I believe I will be able to make minimum weight. I need to speak with you again related to the stut modification.

Thanks for your time (as always)

Try this link for good pricing on used DOT's and slicks. There stock appears to be low right now but that will probably change since the race season is starting up.

http://home.comcast.net/~gduncan2/GT...TiresInfo.html

That could be true, but we'd really have to talk to Hoosier to know if the construction is different. Their webpage only gives the dimensions and available compounds for the various tires.
-edit-
I just emailed them and asked. :)

I just heard back from Hoosier. The 16" tire in question has a 4-ply sidewall, whereas the 15" has a 3-ply sidewall. He said it would work fine for my 1900lb autocross car. :D

When I was doing my research a few months ago the 16" Hoosiers had 3/4'-1' wider tread area over the 15". I have all but decided on the 16" and I think I was looking at the R35. I would need to look at Hoosier's site again. I think I am going to run the FD in SM2 this year and work on the FP car for next year.

I'm going to recant after talking to a Hoosier distributor.
While the 15" tire could work, it would be at the very upper limits of it's load range.
I'm probably going to go with the 16x10. If I can only get the car down to 2000lbs, then I'll run a 16x12 (100lbs weight penalty for going over 10" wide in FP).
Good luck

Don't forget to add the 175lbs for aftermarket fuel control if you are using one.

BTW...what is our hub size?

The F.I. penalty will be fazed out before I finish my car.
What do you mean by hub size? The bolt pattern is 5x114.5.

114.3;) If your ordering Kiezer, CCW, etc then the wheels will be hubcentric. I can't remember offhand, I think they're 57.xx mm, search, and ye shall find. Carl