mc-integra111 wrote:

I get 76 in for your tire diameter (=pi()*(235*0.5*2/25.4+15)). If you actually measured 73 in, then use that. The best number to use is the revs/mi number that the tire manufacturer provides. If you don't know this number, see if Tire Rack has this number for your tires. If you still can't gets revs/mi, then you can calculate it.

revs/mi = 5280*12/Tire Circumference

Once you have the revs/mi number for the tire, you can calculate the required ratio as follows.

ratio = GearX*GearFinal*revs_per_mi/60

Where Gear final is your final gear and GearX is the gear ratio you are calculating for.

Excellent. Although I'm totally math challenged, I think I can figure this out now. TireRack did have the revs/mi for my tire

so that makes it easy.

Thanks for the help!!!!

J