Thread: How To Calculate Tire Size

2 x width x side wall / 2540 + rim size = Tire dia.


205/40/17

2 x 205 x 40 / 2540 + 17 = 23.45


91-94 SER tire 185/60/14

2 x 185 x 60 / 2540 + 14 = 22.74


91-93 NX2000 195/55/14

2 x 195 x 55 / 2540 + 14 = 22.44


95-98 200sx SER 195/55/15

2 x 195 x 55 / 2540 + 15 = 23.44

Cool, this is calculator is pretty handy too:

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

Boo for the easy way, we need to use our brains. Good link though

ZOMG i'm actually speeding on the highway, hmm maybe i should slow down

This is very useful;

Tire size calculator

There is also a formula located in the SR20 Gearstack Worksheet in this section

Just in case anyone has a brain dump, I added it in so you could see how changing your overall tire diameter will change your RPM/MPH ratio.

My example is this: ((205)(.55)/25.4)(2)+15= 23.87 on the worksheet. To find the tire circumfrence, obviously take 23.87 and multiply by Pi.

Dre's way is faster though