tire diameter calculator

[brownbear]

here's an interesting link. http://www.net-comber.com/tirecalc.html

its only metric but will show the difference in tire width/ratio to outside diameter and also shows the difference between original and alternate size and what it will do to the speed indicated.

 

[ace10]

here's another...

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

 

[Junk]

too bad you can't trust the measurements provided by the mfg. I'd rather base mine on actual experience.

 

[NorCalDoug]

I just loaded the formula into a spreadsheet...must just be the geek in me.

In MS Excel, Cut and past the following into F2
=(((B2)*(C2/100) / 25.4)*2)+D2
Where the Width is entered into B2,
the Aspect Ratio into C2, and
the Diameter into D2

E.g. For a 285/75 R16 tire:
Width = 285
Aspect Ratio = 75
Diameter = 16

(((285)*(75/100) / 25.4)*2)+16 = 32.83 inches