Spec Miata Wheels and Tires

Before you go out and spend money on a set of wheels for a Spec Miata, have a close look at the current SCCA class rules:


Wheels/Tires
Any wheel/tire may be used within the following limitations:
a. Required rim diameter is fifteen (15) inches. Maximum rim 
width is seven (7) inches. Minimum weight of wheel shall be 
13 lbs without spacers.  All four wheels must be the same 
dimension including offset.
b. All wheels must be one-piece metal castings (not multi-piece 
wheels, bolted, riveted or welded together).
Tires:
1. National Competition
All cars shall use the Toyo Proxes RA1 (205/50R15).  
In addition, the Toyo R888 will be allowed through the 
second national race weekend in each division.  Starting 
with the third national race weekend in each division, all 
cars shall use the Toyo Proxes RA1 only. The only modi-GCR - 544
9.1.8. Spec Miata Class Specifications
fications allowed to  tires are having treads “shaved” or 
“trued.”
2. Regional Competition
Any DOT approved tire is permitted. Racing, recapped, or 
regrooved  tires are not allowed. Tire size is unrestricted. 
The only modifications allowed to tires are having treads 
“shaved” or “trued.” 


In a nutshell:
Spec Miata will run with acceptable results on Stock wheels.  If you are going with aftermarket wheels to take advantage of the widest permissable wheel size (15x7), there are vendors out there who offer lightweight 15x7s with pre-mounted Toyos that have been shaved and heat-cycled -- all you will have to do is bolt them on when they arrive at your door.