Tire size calculator

[Jason94sport]

I have a few tire size calculator sites but none of them will convert 235 sizes to 31", or 32" etc sizes. I would like to see what the best tire size would be for my X that will have the least effect on the speedo readings.
Anyone have a site like that?

 

[Robert]

Assuming your are talking about having a 235 75R15 tire, its calculated diameter is 235/25.4 = 9.25" (width) * .75 (ratio) = 6.94" (profile width) * 2 (both sides of rim) = 13.88" + 15" (rim diameter) = 28.88" total diameter. A tire closest to that diameter will have the least impact on your speedometer. The larger you go, the more it will affect it. A 31" tire would have less impact on speedometer readings than a 32" tire would.