Thats what i first thought, but then i thought if i tighten the tensioner the wheel will go slower, if i simulate flat land or downhill, the wheel will go faster. Don't really know how accurate if would even be. Guess i can ride for an hour on it and compare it to my normal MPH on my road bike. If it is way off, guess i can just hook that sensor up to another road bike i have. The sensor i got is Ant+