I am trying to figure out what tire to purchase for next years Autocross season. I want to stay in the stock class for my 2012 JCW (D-stock). Most of the tires I am looking at are not available in 205/45/17.

Can I use either 205/40/17 or 215/45/17 and still be considered stock? Also what are the advantages or disadvantages of the different sizes.

I am thinking either the Kuhmo XS or Falken RT-615.

Any input on those tires and sizes that they are available in is appreciated.

 

You can mount any sized tires (street or R-comps) you can fit on OEM sized rims and stay legal in SCCA stock classes. Check www.tirerack.com for available sizes. A slightly shorter tire than stock should improve cornering a bit, and also lower effective gearing a bit (may not be noticeable by feel). A taller tire than stock should provide a slightly better ride, and raise effective gearing a bit.

 

When posting a question about autocrossing you can use this forum-
https://www.northamericanmotoring.co...ms/d-stock-54/

If you are in D stock class you can use either-

R compound tires like Hooiser A6 or Kumho V710
or
Street tires of any treadwear.

The tires can be of any size that will fit on your stock wheels +/- 0.25" on offset if you choose aftermarket wheels of the same diameter and width as stock.

You don't really want to use a tire size that is taller than stock tire diameter so 215/45-17 is not the best option.

205/45-17
205/40-17
215/40-17
are all workable sizes that will fit a stock 17x7 rim.

Street tires will not be as fast as R compounds but you don't have to change them out at the event and can run them on the street. If you are just starting to autocross then street tires are OK until you get more experience.

Common good street tires would be (Extreme Summer tires)
Dunlop Direzza Z1 Star Spec
Or
Bridgestone Potenza RE-11

 

you don't have to run those sizes. Per SCCA rules you can run ANY 17x7 wheel, and ANY tire you can fit on it even if it's a 235.
For AutoX wider is better. 1st you need to decide if you are going to run an R compound or street tire, then check tires for those rules.

 

stock + street tires = road tire class, either front or rear wheel drive. You compete against all stock classes on street tires with 180 or higher treadwear adjusting one's time by the PAX index for your normal stock class. Some regions still have one or more local only street tire or rookie classes that do essentially the same thing.

205/45-17 Bridgestone RE-11 $193
205/45-17 Continental DW (only competitive in the rain) $126
215/40-17 Dunlop Star Spec (does not like high ambient temperatures) $177
215/45-17 Kumho Ecsta XS (does not like low ambient temperatures or rain) $131
205/45-17 Yokohama AD08 $178

Toyo R1R and Hankook R-S3 will not be legal in 2013 due to 140 treadwear.
Prices are available at tirerack.com

 

In addition to D stock you can use Street tires and run in Street Touring X for SCCA.

This may be a good class for you depending on whether you have much competition.
STX does not allow R compound tires.

You can use the Falken Azenis RT-615K
215/40-17 on stock rims, treadwear 200

 

All good info...I run 17x7 wheels with 235-40-17 Star Specs in local street tire class. Not a lot of clearance, but it doesn't rub if you find the right offset, which I did to stay in stock class.

I had a lot of success running 215-40-17 before, although the diameter on the 40 series tires is smaller than stock, which you may want to think through if it's a daily driver.

 

What off set are my stock challenge spokes. 48? Ideally a second set of those would be great but they are too expensive.

 

Interesting that the DW's are competitive in the rain. I have a set of DW's on my stock wheels and some Star Specs on another set of wheels, and the difference in the dry is VERY noticeable. The Star Specs are far superior, it seems. I guess the equalizer is rain.

That said, I was very impressed with the grip I had during a VERY wet Auto-X recently with my Star Specs.

 

I haven't seen the DW run in the rain but by reputation in the Street Touring ranks they are quick. I can confirm your observation that they are considerably slower than Star Specs in the dry.

 

I found a used set of V710's in 225-45-17 size. Which isn't ideal, but workable.

How would those tires work on 17x7 aftermarket wheels for DS on a MCS?

Also what offset is best?

215-40-17 is probably a better size, but this is a case of finding a good used set for $0.60 on the $1, so might be willing to make a little compromise.

 

Great rundown of street tires available to run. I +1 the Star Specs for the money you can't beat them. Last I looked they were running $147 per in the below size.

What will be the min treadwear required for the 2013 season?

 

Minimum road tire class treadwear increases on January 1, 2013 from 140 to 180.