crazy tarzan
+1y
1"=25.4 mm
On my '93 b2600i the stock tire diameter is 26.1"
On any metric tire you can figure the overall size by typing in the following (same as above, I just put in the actual measurement for inches):
XXXmm (width) x .XX (aspect ratio-2nd number) x 2
then divide by 25.4 and add the rim size (in inches), you now have your overall height.
Realize that aspect ratio is how 'tall' the tire will look from the edge of the rim and you can have a wider tire with a lower aspect ratio have the same height as a skinnier tire with a taller aspect ratio.
ie: 195/70 r 15 will have a 5.76" tall sidewall (top and bottom) 26.52" overall height
245/60 r 15 will have a 5.79" tall sidewall (top and bottom) 26.58" overall height
If your overall height varies from the original it will affect your speedometer. A larger tire will cause your speedo to be slower than actual speed, and a smaller tire will cause the speedo to be faster than actual speed.
If you have issues with excess speed and the guys in blue, put smaller tires on and forget it changes it. . .