I just started autocrossing this summer and am already hooked. I'm getting a second set of wheels and need some advice.

Planning to run on Rota Slipstreams and Kumho Ecstas. Don't want to get too sticky on my rubber yet since I'm new at this. OE wheels are 15". I'm wondering what set up you all use. 15" wheels or 16"? How wide can I go in tire size- 205? What should the off-set be? Any other considerations?

I'm looking at the 15x6.5/4x100 + 40mm offset and 67.1mm bore for the rims. Is this best or do you guys like 7" vs. 6.5 and what about bore? Other option is 73.

Thanks!

 

From the SCCA rule book:

13.4 WHEELS
Any type wheel may be used provided it complies with the following:
it is the same width and diameter as standard, and as installed
(including wheel spacers if applicable) it does not have an offset
more than +/- 0.25 inch from a standard wheel for the car. The
resultant change in track dimensions is allowed.
Wheel spacers are permitted, provided the resultant combination
complies with the offset requirements of this section. Wheel studs,
lug nuts, and/or bolt length may be changed

Not much offset change is allowed, so I plan on replacing my 15 inch wheels with "factory" 16 inch wheels. I would like 17s, but they are considered "dealer installed" and therefore not H Stock legal (diameter).

As for tires, if you're just getting started, stay with high performance "street" tires, like the Kuhmo MX or XS, Dunlop Direzza Sport Z1, or something along those lines. R compound tires, "Race" tires, will have more grip for sure, but they will mask some driver faults and mistakes, and the first thing you need to improve about your car is the driver. Street tires are more "forgiving" at their limits than race tires, street tires will warn you when you approach their limit and be a little more forgiving when you go beyond their limit, race tires, not so much.

Remember, a first rate driver can do more with a second rate car, than a second rate driver can do with a first rate car. Welcome to the addiction.

 

I would go with a 16" x 6.5" wheel as light as you can afford. You can only install 15" x 5.5" or 16" x 6.5" the 16" gives you an additional 1" of tire width.

16" x 6.5" wheel offset is 50MM so an offset +/- 6mm is all that's allowed.

With a 16" wheel you can install a 215/45 tire if you select the Kumho XS (as this is the only great autox tire in this size. The widest you can do in a 15" size is 205.

As for the bore as long as the hub bore doesn't exceed the wheel bore you can use wheel centering rings to help with that.

 

Ok, thanks guys. Already revised original plan. Now thinking:

16 x 6.5 Rota Slipstreams
Offset 50mm
215/45/16 Kuhmo XS

Thoughts? And to confirm- none of this is going to bounce me from H stock, right (OE wheels are 15")? Besides the increase in tire width, what are the other benefits to moving from 15" to 16"?

 

I went from 16" to 15". The 15" Holies are lighter and you can have a smaller circumference tire, which will help your gearing. All this aids in acceleration which is an MC's handicap. There's actually a reasonable selection of tires in the 225/50-15, which is a tad wide for such narrow wheels, lol. The other thing is, 15" wheels and tires are cheaper to purchase.

I don't think there's a regulation for the width of the tires is there? It's pretty much run what you can cram in the wheel wells.

I run the Dunlop Z1s on my 15" and am perfectly happy with them.

BTW, I don't think you can fit 16.5" wide wheels on your car.....not stock. LOL

 

Holy carp you're right! Thanks for catching that- corrected it.

 

let me add that a 225/50 15 is 6mm taller than a 215/45 16 so the shorter tire, gearing goes to the 16" 215 size. Now a 205/50 15 (popular size) is 7mm shorter than the 215/45 16 so the gearing advantage goes to the 15 while 215 width takes a lead. While the gearing helps it doesn't make as noticable of an improvement as wider tires. In other words the acceleration gained is outweighed by the additional lateral grip and speed through the turns. Also the 16" has a shorter sidewall which reduces sidewall deflection. I ran a 615 in the 205/50 15 size for years, but when Kumho came out with the XS in a 215/45 16 size I sold my 15" wheels and tires and never looked back.

As someone said in this thread there is no restrictions on tire size just wheel size. I found the 215/45 16 the fastest for me.

 

225/45/15....Wide footprint, diameter less than stock. Best of both worlds....

I went from 205/50/15's to 225/45/15; much prefer the latter.

 

Besides the Ventus R-S3 and the Hoosier A6 what 15" autox tire worth the price comes in that size?

Tire size selection is better in 16" than 15". Personaly I run my R50 in ST and have done quite well in the 16" wheel size.

I'm still waiting for that SWEET size of 225/35 16!!

 

Toyo Proxes Ra-1. I saw the Nitto NT-01 for $140/tire on www.discounttire.com. Which doesn't sound like a bad deal. If only tirerack.com carried them and had some test results on them.

Gotcurves, why stop there? As long as your ride height isn't too low, I'll bet we could stuff some 235/25-16s in there. Aaaaah, some day. lol.

 

NT-01 can be had for close to a hundred bucks in 225/45/15. Nitto's parent company IS Toyo; the compound in the NT-01 is identical to the compound of the Toyo R888's, just different tread pattern. Not sure about the RA-1, that may be a slightly different compound.

Nice thing about the Nitto-01's (and the R888's) is that they start at 6/32 tread depth, they're ready to go out of the box, the RA1's start at 8/32 and really should be shaved....

 

So if I want to run on 17s, what class would that put me in? I don't really care about what class (I'd run with lambos if I had to), I just don't want to be disqualified.

 

I believe that would put you in STS. Then you'd be able to do a whole bunch of things to your car. 7.5" wide wheels, sways all around, camber plates, coil-overs, bushing material. Geez...are we competitive in STS? I don't think I've ever seen a Cooper in STS at the autoXes that I've been to.

 

The Slipstreams (or Boosts) available for $500 shipped from either 18racing.com or wheeldude.com are tough to beat. Buy tires from the same source and save a bunch on mounting/balancing as well.

On tires: The Ecsta XS sounds like a good pick if you aren't wanting to jump straight into R tires. They are aggressively priced, and they performed very well in the ST tire comparison published earlier this year in Grassroots Motorsports.

The Nitto NT-01s are not available in a MINI-friendly 16" size unless there's something new out there that I'm not aware of. It's a shame, as it's a great compromise tire for very low cost. The corporate-cousin Toyos mentioned are a fair bit pricier; more than what Tire Rack is currently asking for Ecsta V710s.

One plus with 15": bargain-basement deals on used 15" race tires seem to be ever present (very often free). I'm not suggesting that you could contest for a national title on Spec Miata cast-offs, but this is a great way to get your feet wet. Maybe do this with your OEM wheels and buy something pretty to enjoy on the 350 days a year that you're not autocrossing .

 

16"x6.5" wheels were standard with the Sports Package, and they were available by themselves as a factory option. You can legally use this size without making any other changes to your car.