Hey guys...

I have an '09 Cooper with the stock 15-inch wheels...I believe they are 5.5 inch diameter.

I just finished the autocross season using the stock all-season tires.

I'd like to improve my times next year with the help of better tires, but I don't want to buy a whole 'nother set of wheels/r-compund tires, and the Rio Grande SCCA has a "street tire" multiplication factor, so r-compound tires have less significance anyway.

I guess I have to stick with all-season tires, as even though I don't have to drive in the snow, it does get cold here in Santa Fe, NM (nights in the teens and lower), so summer tires are out (but I could be talked into them <g>).

And...just how cold does it have to be to really compromise a summer tire's performance? If I drove at temps, say, of 40F and higher, would I be OK? I can drive my other car when it's snowy/cold.

My basic questions are:

What is the biggest/widest tire I can fit on those 15-inch wheels?

And secondly, can I use summer tires if I only drive on them in the middle of the day when temps are higher?

Thanks...

 

Temps below 40F are the consensus point for not driving on summer tires.

For the best hot weather autox performance, I recommend 205/50-15 Kumho Ecsta XS. They are lighter, as fast, and less expensive than the other alternatives such as Toyo RIR, Dunlop Star Spec, and Bridgestone RE11.

 

+1 Especially if you plan to keep the All-Season for street and the XS for auto-x, keep in mind the XS are not that great in rain.

 

I saw the Kumho on TireRack...looks like an excellent choice.

I read somewhere that 205/55-15's would be better as they are closer in diameter to the OEM tires?

And OK...if I had to go with an all-season, what's a good, less-than-$100 choice?

Thanks so much.

 

The 205/50-15 Kumho is 23.1" compared to 24.0" OEM. Note that your speedometer will be even more inaccurate than it is with OEM tires. I use a Garmin navigator even when running 175/65-15 tires due to a 4 mph error at 66 mph. The smaller diameter would lower your sidewalls and ride height by 1/2 inch while providing lower gearing.

All season choices:
195/60-15 Bridgestone 960 (24.2")
195/60-15 Yokohama Avid Envigor (24.2")
205/50-15 BFG g-force Super Sport A/S (23.1")
205/55-15 Continental Extreme Contact as (23.9")

 

If you're thinking of autocrossing and wanting the widest tires for your 15's,
you would do much better with summer tires than all-seasons. Get some
all seasons or winter tires on cheap rims for the winter.

205/50/15 -Dunlop Direzza Sport Z1 Star Spec or Yoko Advan Neova AD08
are probably the best performing ones that will fit.

 

Wow...looks like you have really done your homework...thanks so much. Yeah, the speedometer error is just horrendous...I realize it's German (or is it Eurropean Union) law, blah, blah, blah...but GEEZ...

Your opinion about the relative strength of grip between theses all seasons and a summer tire?

 

I currently have 205/55/15 on my car and they're great on stock 15 inch "spooler wheels". The 205/50/15 are lower profile with better cornering but the diameter is off. Alot of people run these though for low profile, cornering and autocross. These would be the biggest (widest) on a stock 5.5 inch rim. The biggest that I have seen (in "Show me Your Wheels") is 225/50/15 but they are on 7.5 inch rims.. I did months of research as I could not find the answer to your question either. Now I am confident that I can share this information with any motorer. Cornering is phenominal. I have Kumho Ecsta's from Tirerack. Hope this helps.

 

+1 on the Kumho Ecsta XS for Auto-X. I have them mounted on my 15x7.5 rims and they are amazing! Cheaper than Direzza Star Spec, very sticky. Most importantly, since they are NOT uni-directional, you can rotate left to right AND front to back to make them last a little longer!

 

"Your opinion about the relative strength of grip between theses all seasons and a summer tire?"

The all-seasons listed are not competitive with the Kumho Ecsta XS or other summer tires previously listed. My Dunlop Star Specs are 2.8% faster than the stock Conti summer tires which are quite good on public roads.

 

For more information look under the thread for "8 inch wide wheels and larger". I think its under "roll call......". Alot of information there about 15 inch wheels and tires.

 

Thanks!