Does anybody have a link to a tire size calculator, im looking to put some 20'' rims and tires on my truck and want to compare different size tires to the stock size.

Thanks

Larry.

 

This is the one I have always used.

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

It seems to work well and it comes up with the same revs/mile
as the ford dealership.

 

The formulas are below.

Example: Stock L has 295/45-18 tires.

- 295 is the tread width in mm.
- 45% of 295 gives you the sidewall height. So 295*.45 = 133mm (or 5.2inches).
- 18 is the rim diameter in inches.
- Total wheel diameter is the rim diameter plus 2 sidewall heights:
18 + 2*5.2 = 28.5inches

(To get mm into inches, divide by 25.4)

So a Proxes S/T 305/60-18 would be 32.4inches in dia.
Your speedo would read 28.5/32.4 = 88% of your real speed.

My .02: screw the speedo and go for looks. You can always work on reprogramming the speedo as your next mod/fix.

 

Im going to get some 99 style Lightning rims in 20`s with 295/40/20 goodyear tires, will these tire perform as good or better than stock?, the tire calculator above was very helpfull.