Stock is:
225/75/16 w ith 3.55 gears

Now I have:
295/75/16 with 4.10 gears

So what is my speedometer suppossed to read? I actually think I am pretty close to stock but I just wanted to see if there was a formula out there to figure it out.

Brad

 

here's a gear ratio calculator:

http://www.drivetraindirect.com/t_gear_calculator.htm

here's a Tire size compar-o-meter:

http://www.miata.net/garage/tirecalc.html

I think this procedure is accurate:

Take the tire sizes in inches(to the tenth of an inch), the gear ratio, a constant speed the OD is engaged at (60 mph) and the OD ratio of 0.69 andcalculate the RPM's forstock and aftermarket.Then subtractthecalculatedstockRPM from theaftermarket RPM'sthen dividethat number (very small positive for you) by thestock RPM.Multiply the answer by 100. That's the percentage that the rpm's differ, which if you read yourRPM'sat 60 MPH is how far off you are. You're really close to stock. like 1.4%@ 60MPH. I wouldn't worry about it.

 

Thanks aim4squirrels...I figured I was really close and I did those calculators but did not know my OD ratio...Thanks again.

Brad