Originally Posted by GAS GUY
Im not sure , you may be right,but it sure dont seem like 20 % judging by the ride to work.
Until I get a good check against the gps I wont know.
I did compare the speedo to the gps on a few rides and it seemed to be about 10%.
The 19" tire probably has a taller sidewall than the 21" tire,so that may make up for some of the wheel size.
EDIT: Found a conversion calculator online and it appears to only be a 4 % change.
I also remember the speedos are off anyway even with the stock wheel,but I believe the Odo is pretty accurate.So 4% seems right.
I assumed a 17" wheel for my estimate.