Gary must be typing while he's asleep at the computer again (see his avatar image).

With the larger rear tire, the engine will be turning at a slower RPM for the same road speed.

The factory speedo error did not always show in the odometer too. But your new shorter tire will result in an odometer error now. The 130/70 tire is spec'ed at 25.1" diameter, the 130/80 tire is 26.6". That's approx 6% difference. Since circumference (the linear distance a tire rolls in one revolution) is Pi x diameter, the same percentage difference applies.

Best way to find the error is to compare against a GPS. I don't have a GPS so I find the stationary radar units with the big digital display and make a run at it. Which is not easy since a bike is so much smaller to reflect the radar waves back, the radar will pick up all the other cars and trucks nearby more readily (this comes in handy when there is a LEO operating the radar).



duke
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