This Calculator I made, it go a step frther that 1010tires It calculates gears vs RPM vs Speed as well..
Calculators:
This is a Microsoft Excel Worksheet the calculates Rear End Gear changes and there effects to RPM and Speed. Also there is a calculator that will assist you in selecting the correct Tire size for your car including what Wheel and Tires combo will fit.
Download the sheet here.
http://home.comcast.net/~swieduwilt0...lculations.xls
you can get an excel viewer that plugs into your browser here:
http://www.microsoft.com/downloads/d...displaylang=EN \