Originally Posted by
twobikes
. In a 14 mile ride there is still about a tenth of a mile difference between their readings, but either one of them can vary a tenth of a mile on different days. I do not know why.
1) tire inflation on the particular day.
2) your weight that day.
3) the exact path you took around turns.
4) rounding error.
Unless you do a rollout before each ride, there's always going to be a little bit of calibration error.
Given that we're not trying to hit a target on the Moon, or landing the bike by instruments on a dark runway, I find the numbers in the chart with the computer sufficiently accurate for my purposes.