Tire Size and Circumference
As the rear tire is a major part of the total gearing of a motorcycle it is important to use the correct size for the rear tire in the GC.
The tire size consists of 3 fields, the tire Width in millimeter, the tire Aspect (= height in % of tire width) and the Rim diameter in inches. Not very consistent but that's the way tire manufacturers do it. An example is: 190/50/17. This means 190 mm wide, 50% of 190 mm high and a 17" rim. Using this data the GC calculates the tire circumference which is used to calculate the speed of the bike.
Theoretically, a Bridgestone tire 190/50/17 should have exact the same sizes as a Michelin 190/50/17 but in reality all tires are different. Hell, even 2 Bridgestone's aren't the same. Because this influences the accuracy of the GC, as of version 5.1 I have added a field called 'Tire Circumference' which you can use to adjust the calculated to your actual tire size !
the default tire size from its database to calculate the tire
circumference and shows it besides the tire sizes. Now if you know that
you tire circumference is different you can enter it in the field called
'Tire Circumference'. GC will then recalculate the sheet using your
entered actual circumference.
How to measure your actual Tire circumference:
This all great but now you need to find out your actual rear tire circumference. You could wrap a tape measure or a string around your rear tire but that is quite complicated. You could also do the following: