About

Changing sprockets is the most common modification for adjusting a motorcycle's character. Dropping a tooth on the front sprocket increases acceleration (torque) at the expense of top speed. This calculator quantifies that percentage change. Crucially, it includes a Chain Wear Indicator. Ratios that result in integers (e.g., 15/45 = 3.0) cause the same chain links to hit the same teeth repeatedly, accelerating wear. Optimal gearing uses "hunting tooth" combinations (coprime numbers) to distribute wear evenly.

Formulas

The Final Drive Ratio is determined by the rear sprocket teeth divided by the front.

Ratio = Teeth_rearTeeth_front

The percentage change helps visualize the impact on the speedometer.

%Change = Ratio_oldRatio_new − 1 × 100

Reference Data

Change	Effect on Torque	Effect on Top Speed	Typical Use
−1 Front	+4% to 7%	−4% to 7%	Track / Wheelies
+2 Rear	+4% to 6%	−4% to 6%	Stunt / City
−2 Rear	−4% to 6%	+4% to 6%	Highway / Touring

Frequently Asked Questions

It refers to a sprocket combination where the number of teeth share no common factors with the number of chain links. This ensures a specific chain link hits a specific tooth as infrequently as possible, extending part life.

On most modern bikes, yes. The speed sensor often reads off the transmission. If you change gearing, the bike thinks the wheel is spinning at a different rate than it actually is.

Roughly, yes. A typical front sprocket is 15-17 teeth and rear is 45ish. So 45/15 = 3. Changing 1 front tooth is a ~6.6% change, while changing 3 rear teeth is also ~6.6%.

Select your motorcycle from the dropdown. We populate the factory Front and Rear sprocket sizes so you can see exactly how your custom setup compares to the manufacturer's design.