Originally Posted by tahoeacr
I'm way past 40 but I'll tell you anyways. With my bike when set on 21 the speedo is accurate and the Odo sucks. When set at 19, the speedo reads fast by 3 or 4 mph. The Odo is off 1/10th per 5 miles with a knobby on front. I use both odo and GPS.
Maybe you got it upside down? When speedo set at 21 it reads faster so to give us a safety margin of 8% odo is accurate? what speedo does is multiply revolutions X circumference - smaller circumference = lower speed