I have gone from stock 25" tires to 27" Mudlites Does anyone knw the formula for figuring out the true reading on the speedo
Thanks

 

Measure the exact center height of the tire with the sensor. Multiply the height by 25.4 to convert to millimeters. Then take that number and multiply by 3.1416. This should be the number you enter. If you need to convert back to inches then divide the last number by 1.61. I don't need to convert back to inches with my speedo but some require it. Hope this helps.

 

I think I have it worked out but I may be wrong as it is kinda drunk out tonite
27" tire is approx 8% bigger in circumfrence so speedo should be out by the same gives me a top speed of approx 100 Kmh