Changing your wheels/tyres may effect your speedometer reading!
With this new combination your speed will be % of that inidicated.
When your speedo reads mph you will actually be doing mph
Points to note:
1 inch = 25.4mm (Tyre & wheel manufacturers mix mm and inches in their ratings)
Remember: A Speedometer error means an odometer error too!
* As tyres deform under load, a tyre does not roll like a solid wheel. It's Rolling circumference is calculated using a deformation factor (DF) x total diameter x pi. DF is typically 0.96 . If required, you can change the deformation factor here: