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How-to guide

How to clean, check and true disc brake rotors

Spot a contaminated, worn or bent rotor, clean it with what Shimano and SRAM recommend, check the wear limit and straighten light bends with a truing fork.

Last edited Nov 8, 2026 by Pedalwise team Edit History Add a subpage

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Difficulty
Moderate
Time
20 to 45 minutes

Tools

  • Rotor truing fork
  • Flashlight
  • Measuring caliper
  • Clean rags
  • Isopropyl alcohol

Rotors can pick up oil and grime, wear thin, or bend. This guide covers spotting a contaminated or bent rotor, cleaning it with what the makers recommend, checking it against the maker's wear limit, and light truing on the bike. For pad problems, see replacing disc brake pads.

Don't ride a bike with weak or unreliable brakes. Shimano says that if the lever feels sluggish or gives no resistance, stop using the brakes and see a professional (Shimano dealer manual).

E-bikes are usually heavier than regular bikes and speed up quickly, so Bosch advises learning how yours handles and brakes, and checking the brakes regularly (Bosch eBike guide).

Rotor edges are sharp and can cut you, especially while the wheel is spinning (Park Tool).

1Look for the signs

  • Squeal, extra lever effort, or a dark rotor that smears when touched can mean contamination from oil, grease or brake fluid (Park Tool).
  • Discolored rotors need cleaning or replacing, and some surface wear is normal (Shimano maintenance tips).
  • A rub or noise as the rotor passes through the caliper usually means it is bent (Park Tool).

Photo needed: A clean rotor next to a dark, glazed rotor. Add one

2Rule out other causes of rub

Before truing, Park Tool says check that the wheel is fully seated, the hub has no play, the caliper is aligned, the pistons aren't sticking, the cable isn't dragging on mechanical brakes, and the rotor bolts or lockring are tight (Park Tool). See adjusting mechanical disc brakes.

3Clean the rotor

  • SRAM recommends isopropyl alcohol for cleaning rotors (SRAM troubleshooting).
  • Shimano says clean the brake system with soapy water and a dry cloth or isopropyl alcohol, and not to use commercial brake cleaners or silencing sprays, which can damage seals (Shimano dealer manual).
  • Find the source. Park Tool lists spray lube overspray and hydraulic leaks as common causes (Park Tool). Bosch says keep chain lube off disc brakes (Bosch eBike guide).
  • If oil has reached the pads, cleaning the rotor isn't enough. Shimano says oily pads are a reason to replace them (Shimano dealer manual).

Photo needed: Wiping a rotor with a clean rag and isopropyl alcohol, with the pads removed. Add one

4Check rotor thickness

  • Measure the braking surface and compare it to your rotor maker's limit.
  • Shimano says stop using the brakes and see a dealer when its rotors are worn to 1.5 mm or less, and to replace any rotor that is worn, cracked or warped (Shimano dealer manual).
  • For other brands, use the limit in your rotor or brake manual. If you can't find one, ask a shop.

Photo needed: A measuring caliper on the braking surface of a rotor. Add one

5Find the bend

  • Spin the wheel and watch the gap between the pads. A flashlight or white paper behind the caliper makes the wobble easier to see (Park Tool).
  • Mark the spot. Numbering the rotor arms helps track progress (Park Tool).

6Bend it back gently

  • With a rotor truing fork, bend the rotor the opposite way to the wobble. Start with light pressure and add more only if nothing changes (Park Tool).
  • On two-piece rotors, bend only at the outer ring, never at the arms (Park Tool).
  • Repeat until it spins without rubbing the pads. Park Tool says that is straight enough (Park Tool).

Photo needed: A truing fork on the outer edge of a rotor at the bent spot. Add one

7Know when to replace it

Park Tool says replace a rotor that is badly bent from an impact, shows no improvement after a few minutes of truing, or leaves you unsure (Park Tool). If you fit new rotors, bed them in.

8Test before riding

Spin the wheel to confirm there is no rub, and check the lever engages firmly with good stopping power (Park Tool). Work the lever a few times before you ride (Shimano dealer manual).

Videos

How to True a Bicycle Disc Brake Rotor from Park Tool: Finds the bent spots on a spinning rotor and straightens them with a rotor truing fork until it runs clear of the pads.

When to get a pro

Sources

Stuck after these checks? Find a shop near you.

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If these steps didn't fix it, find a shop near you in our partner network. For battery or wiring trouble, look for shops marked Battery and electrical.

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