A year ago I purchased my '02 MSC with white 15" holies and Continental tires. I changed to 17" chrome rims with Dunlop 9000 run flats and I think they look great. I am considering trying a bit of autoX. I am wondering what size rims and tires are best for track/auto cross? Should I use 15s? I have two sets of 15s. The holies and a set of silver 15" five stars with new OEM stock Pirelli tires. I really know little to nothing about what would be best. I'd appreciate opinions!

 

Check with the officials of your proposed autocross event (is it SCCA?).

Determine what class you should participate in.

Since you don't have a reduction pulley (Yet) then you are not in Street Modified which is highly competitive and allows for any wheel and any tire.

You have a cold air intake so that bumps you out of stock class which would be the best for you. You'd have to remove all upgrades (other than cosmetic) to participate in G stock (you can keep the cat back exhaust).

If you use street tires rated at least 140 treadwear then you can run in STX and if you want to run R compound tires then you are in D Street Prepared.

Given that your best set of rims will likely be the silver 5 star stock rims but I think they are 16" not 15".

16x6.5 stock rims allow for some good autocross tire sizes- see G-stock forum for particulars.

15x5.5 stock rims allow for 205/50-15 and usually Kumho V710 would be the best R compound (not allowed in STX class). This combo can be used for DSP class.

The 17" chrome wheels are heavy, not good for autocross.

 

If you just going to test the waters I'd go with AZENIS RT-615 205/50R15 on your 15" rims. The better choice would 215/45R16 on your 16's. Both tires have reinforced side walls. I run the 215's on the street. The shorter tire give you better acceleration. You would run in SCCA STX class because you have the cold air intake and M7 STB.

 

I would say go for a while and learn how to drive before getting too worried about things. I think you already understand but the 18s would not be a good idea for autocross. Id just go with either of your 15s and pick the ones with the strongest sidewalls. At this point youll have a while to learn how to drive and you wont be set up for a very good class anyways, so just go for a stiff sidewall which should give you more consistent grip and just learn and have fun. If you are serious about autocrossing later going stock really is the mini strong point.