Rear tire diameter...
 

To those of you with Hawks, Tt250s, etc with the 18" rear rim, my question to you all is this: what is the outside diameter of your TIRE.

I own a Brozz with the 19/17 highway combo, and in order to decide on a new rear sprocket, I need to make an educated decision on the ratio I want. Trouble is, outer diameter plays a huge role on output rpm. Need an example? If you compared the outside circumstances of a 17" tire and an 18" tire, the distance is different. At rpm, the taller rear tire makes fewer revolutions to achieve the same distance as a smaller tire at a higher rpm. Maybe the difference is minuscule, maybe it's not.....but I'd like to calculate the difference and adjust my choice of rear sprocket accordingly.

Thanks in advance!

Nvm, I found an online calculator that uses tire sizes to calculate tire circumstances.... here's where we stand:

The factory tire listed on therps.net is a 110/100/18, which equates to a 26.661 inch outside tire diameter and ultimately, a circumference of 83.758 inches.

For sake of comparison, the factory rear tire on my 2016 Bashan Brozz is a 110/90/17, giving it an outside diameter of 24.795 inches, and an outside circumference of 77.896 inches.

That means that a Hawk's rear tire revolves 780 times per mile, while my rear tire revolves 838 times in order to travel the same distance!

Good info, This is why we are slighty higher rpms with same sprocket set ups as the guys with the 18" back wheels. Thanks for posting specs!

Good info.

When I replace my rear sprocket I will be going with a 45 or 43 tooth instead of the 46 I have now. Maybe I can get a few more mph out of it.