Originally Posted by Nuggle

Recommended for the toyo T1R

245/35ZR20 8.0-8.5-9.5" - 776 RPM this set up your off by -20 RPM
275/30ZR20 9.0-9.5-10.0" - 782 RPM this set up your off by +4 RPM
&
255/35ZR20 8.5-9.0-10.0" - 769 RPM this set up your off by - 27 RPM
285/30ZR20 9.5-10.0-10.5"- 776 RPM this set up your off buy -2 RPM

The front tire rpm will be off too much from stock you will notice a diffrence

Combo
245/30ZR20 8.0-8.5-9.0" - 801 RPM this set up your off by +5 RPM
285/30ZR20 9.5-10.0-10.5"- 776 RPM this set up your off buy -2 RPM
would be nice too but i am not sure if 245 and 285 will work properly

but the best set up would be

245/30ZR20 8.0-8.5-9.0" - 801 RPM this set up your off by +5 RPM
275/30ZR20 9.0-9.5-10.0" - 782 RPM this set up your off by +4 RPM

On a 05 6MT or 06 model stock is
225/40ZR19 7.5-8.8-9.0" 796 Rotations per mile
245/40ZR19 8.0-9.0-9.5" 778 Rotations per mile

FYI the middle number is the suggested rim diameter