[Cobra #3170]

Originally Posted by G-Pete

15 inch for street and 18 inch for track, really?

Now watch this video of Bill Shepherds Cobra....


Nurburgring Aug 2010 Cobra incar footage - Bill Shepherd Mustang - YouTube



.....he is running 15 inch. Tell me again about 15/18 street/track again.

You put him on 18" Hoosier A6's with proper camber and spring rates and he would pick up 6 seconds a lap. I ran 15" back when they actually made good slicks for 15's (1970's), LMS 16" slicks in the 1980's and 1990's on wider than stock rims (9.5 F and 11 R) and now 18" on (11" F and 12" R) and I can tell you there is no comparison. Yes, part of it is modern compounding but the steering response is so much more precise with low aspect ratio's I would never go back. There is also the problem of tire distortion under high loads
with large aspect ratios especially with poor suspension geometry. There is a reason that the automobile and tire companies gravitated toward larger wheel diameters, they are better.