beachboy23

I am in the market for buying a new set of tires for my 1999 GS400. The recommended tire size is 225/55R16, but there are variations in tire diameter even within the same size. For example:

Bridgestone Turanza LS-Z 225/55ZR16: 25.9"
Bridgestone Potenza RE960AS 225/55WR16: 25.7"

How does one calculate the ideal tire diameter so that the speedometer and odometer read correctly?

V8_Aristo

Usually tire diameter is measure by tire width, divided by the twice the profile and then adding the diameter of the wheel. If you use this formula on your tire size, it comes out to 25.74". The Turanza might have been a typo, since this is a standard everyone uses to calculate tire diameter. But then again, a 0.2" difference in tire diameter might be still be within specification.