I run 18 in my 275/60 Hoosier DR's. @ 3700 lbs.

Buddy of mine runs the 275/50's on his Mustang & it does not hook as well, those are M/T's. The shorter sidewall seems to be too stiff compared to the 60 series.

Another local I race W/ runs the same 275/60 I run on his 3800 LB BB Chevelle, it works best @ 15-16. Any less than that & traction is worse....