dyno s mesure tq and they also mesure rpm .....tq is the abilty to twist the drum on the dyno...the 2 readings give the dyno the abilty to calculate horse power ...since hp is only a calculation of the 2 readings,,if the rpm reading and the tq reading are accurate then the horsepower number is a math equation....lower gears are tq multipliers this is true but the motor rpm goes up accordingily at whatever the gear ratio change, hope this helps/////