I have seen several threads that somewhat touched on this (for all you search ***** out there), but none where the topic was addressed from the angle I'm looking for (at least, I couldn't dig far enough to find them). I am looking at getting a dedicated set of wheels/tires for auto-x, and I have already modified my car enough that I can no longer run stock. That said, looking for opinions on the positives/negatives of getting wheels in the 17" range (even 16? I don't know), as well as positives/negatives of different widths. By different widths, I don't mean staggering the set up front and rear, just wondering whether/why 17x7 would be a better idea than 17x8, etc. Thanks.

 

The GT models have bigger brakes/rotors and I don't think 16' wheels will fit.

 

The tire size you want to run will dictate the size of the wheel you should run.

A 245/45-17 on a 7" wide wheel would be a tough fit and might run into places that'll refuse to mount them. However, it'll fit an 8" fine. (might prefer a 8.5"/9" for even better results and a more square shoulder).

I'm still reading up on what will actually fit under your wheel wells.... (I've heard 275 Hoosiers/Kumhos) so I can't be called on to suggest a particular tire size for the car... but your wheel width always depends on your tire size you want to run. The wider the tire, the wider the wheel for best results.

--KC

 

My understanding is the smaller wheels are lighter. Lighter is good. Smaller wheels also allow you to get smaller diameter tires. This effectively gives you more torque which is always a good thing in autocross. Smaller wheels require smaller brake rotors. Usually people size wheels to find the smallest diameter that still fits over stock rotors/calipers.

As a general rule wider tires are always better. Some get custom wheels in order to run the widest tires physically possible--or in some cases the widest tires that exist.
________
BIG WOMEN

 

so, we know that 17's will fit on the stock rotors, and over the stock calipers, yes?

 

yeah 17s will fit over the entire brake system

 

The fastest CSP Miatas always run smaller diameter wheels & tires - they lower the car, lower the gearing, and reduce rotating inertia all at the same time - a win/win/win scenario, you might say.

The same logic *should* apply to an RX-8. However, one of the downsides to a lower diameter tire is that, when coupled with a lowered suspension, you may not be able to drive to the event on your competition tires due to ground clearance issues. Whether this is an issue for you depends on you own situation, of course.

In the end, I'd reccomend getting as much width as you can, and not focus as much on downsizing the diameter as much. For example, Kumho makes both a 245-40-17 and a 275-40-17 in the Ecsta V700. I suspect the 275s would ultimately be faster (assuming you could fit the 10" wheel width they rightfully deserve), but that's just a guess. For CSP Miatas, the happy coincedence is that you can get a tire that is both fat and has a small diameter; I'm not sure we have the same luxury for the RX-8.

George