Gear Ratio

A gear ratio describes how many times one gear turns for each turn of the gear it drives. If a 15-tooth gear drives a 45-tooth gear, the ratio is 3:1: the small gear turns three times for one turn of the large one, multiplying torque but reducing speed.

On a motorcycle the overall ratio is the product of the primary drive, the selected gearbox gear and the final drive (chain sprockets, belt or shaft). Lower (numerically higher) ratios give stronger acceleration; taller ratios give lower rpm and higher top speed.

The easiest way to change gearing is to swap sprockets: a bigger rear or smaller front sprocket makes the bike quicker to accelerate but revs higher at cruising speed. The speedometer may need recalibrating afterwards.