What is a better size RT615 for autox. Here in San Diego we run a SK2 class. GS rules, but only Street tires are allowed (for us cheap guys).

205/40R16 (in stock at Vulcan and Edge) Makes me think no one uses this size.
or
215/45R16 (out of stock at Vulcan and Edge) makes me think everyone is using this size.
or
225/50R16 (in stock at Vulcan abd Edge) but will they fit the car in both front and rear without modding, and will they fit on the 16X6.5 rims?

I have the stock 16" X-lites as my autox wheels.

 

What year MINI will make the difference in tire choice.

if late 04-up with the lower gear ratio tranny then the 215/45/16 is the popular choice since its good grip and around same as stock.

If an early model MINI with the old tall gear box then would go with the 205/40/16 the lower profile will put you on the same par as the new tranny on the 45 taller tires. the 10mm smaller width is hardly noticable on a budget

the 225 should fit but will be tight. Being that its a taller tire it may be over gearring the car for some of the small Autox tracks (like the ones in my area)

 

thanks for the reply