CalculatorsBrake Rotor Size Calculator

Brake Rotor Size Calculator

Bigger rotors add leverage and heat capacity. The recommendation follows discipline first, then bumps the front rotor if a road or gravel rider is heavier.

Inputs

Rider weight (lb)

Discipline

Results

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How the number is made

Front/rear in mm: downhill 220/203, enduro 203/180, trail 180/180. Gravel 160/160, or 180/160 at 90 kg and above. Road 160/160, or 180/160 at 85 kg and above.

The frame, fork and caliper adapter have to exist for that diameter. A number here is not a mount. SRAM sells 200 mm where Shimano and most others sell 203 mm, so use the size your brake maker lists.

Related calculators

Fork Sag and PSI Calculator
A long-travel fork and a small rotor is the combination that fades.
Bicycle Torque Guide
Rotor bolts are a low newton-metre job. Over-tightening can strip the hub threads.

Questions

Why is the front larger?

Weight transfers forward under braking. The front rotor does more of the work and collects more heat.

Can I run 203 on a road bike?

Only if the fork is rated for it and an adapter spaces the caliper out. Most road forks stop at 160 or 180.

When does a road bike step up to 180 mm?

Road rotors stay 160 mm until rider weight reaches 85 kg, then the front rotor becomes 180 mm. Gravel uses 90 kg for that step.

Example products

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Disc rotor
Match the mount (6-bolt or Centerlock) and the pad compound to the rotor.
$25–$90