Bike Disc Brake Rubbing

Disc brakes are the alternative to cantilever v-brakes or rim brakes. Disc brakes work similar to automotive brakes in that pistons and brake pads squeeze a metal rotor attached to the hub of your wheel. These are really common on mountain bikes, fairly common on gravel bike, and increasingly common on road bikes.

There are two kinds of disc brake actuation—cable-driven and hydraulic. Cable-driven calipers have a stationary pad on one side and a moving pad on the other. The moving pad is controlled by a cable. These are common on entry-level bikes. Some calipers on higher-end bikes are dual piston, but most are single piston. Hydraulic is actuated by brake fluid in cable lines. They are always dual or more pistons.

If you squeeze the brake lever and it squeaks, check out this troubleshooting page. Visually inspect your rotor as the wheel spins and verify that it's making contact with the pad. If it's not, the squeaking may be coming from a different source. Check out this wiki.

It's possible your brake rubbing is a combination of different issues, in which case you'll need to use multiple methods to fix the problem.

A rotor can be bent in one or more spots. This can happen from braking too hard or manufacturing defects. You know your rotor is bent if the rubbing happens at the same spot every time the wheel turns. To test this, put your bike up on a stand and spin the wheel.

• Try to align the caliper (if the rotor isn't warped much)
  • If the rotor isn't warped very much, you might be able to center the calipers so the rotor doesn't rub on either pad. This is a quick and easy fix to get by.
    • Check out this section to see how to align your caliper
    • Align the calipers so the rotor won't rub on the pads when the wheel spins
• If your rotor is too warped to align the caliper around it, you might be able to bend the rotor back into shape.
  • Spin the wheel slowly while looking down the length of the rotor to identify where and in what direction the rotor is bent
  • Stop the wheel where the rotor bends and mark its location by putting a piece of tape on the spokes. Do this anywhere there's a bend on the rotor.
  • Use a clean crescent wrench or (LINK) rotor bending tool to bend the rotor in the right direction. This may take a lot of force and multiple small tugs. Visually check the rotor after each correction to make sure you're bending it in the right direction. Repeat this process for all bends in the rotor.

• If you're having trouble correcting the rotor while it's mounted to the wheel:
  • Remove your wheel and take the rotor off the hub.
    • Clamp the rotor in a clean vice, with the bent section of the rotor sticking out of the vice jaws.
    • Use your crescent wrench or rotor bending tool to correct the rotor.

This is an example of a rotor that is likely too warped for repair, and should instead be replaced. This is particularly true if the rotor was severely warped in a bike crash, in which case there could be micro-fractures in the rotor.

Your caliper could be too far to one side or twisted. If it's twisted, you'll have reduced braking power.

• Identify the side of the caliper with the stationary piston. You'll get the rotor as close as possible to this piston, leaving room for the actuating piston to squeeze against the other side of the rotor.
• Loosen the caliper mounting bolts enough to wiggle to caliper side-to-side.
• Firmly squeeze the brake lever and loosely tighten the caliper mounting bolts, then release the lever.
• Visually check that the rotor is equally spaced between each brake pad.
• Tighten each bolt in a little at a time, alternating between them as you tighten. Check that the caliper hasn't moved between tightening.
  • If the caliper moves during tightening, the bolts may have worn into the caliper's metal. To fix this, insert thin washers between the bolt heads and the caliper.
• Check that the rotor spins freely between the brake pads. If it doesn't, loosen one bolt at a time, keeping the other slightly tight. Adjust each end of the caliper so the rotor is as close to the stationary brake pad as possible without touching it.

• Slightly loosen each caliper bolt until the caliper can wiggle side-to-side.
• Firmly squeeze the brake lever and loosely tighten the caliper mounting bolts, then release the lever.
• Visually check that the rotor is equally spaced between each brake pad.
• If it is, tighten each bolt in a little at a time, alternating between them as you tighten. Check that the caliper hasn't moved between tightening.
  • If the caliper moves during tightening, the bolts may have worn into the caliper's metal. To fix this, insert thin washers between the bolt heads and the caliper.
• If it isn't, loosen one bolt at a time and make small adjustments until the rotor is equally spaced between the brake pads. In the end, make sure the rotor is exactly parallel to the brake pads.

This happens because pistons get dirty and they can't slide freely between the caliper body. You'll know your pistons are stuck if one or both sides of your brake pads are too close to the rotor.

• Take off the wheel and remove your brake pads.
• Look inside the calipers at the metal cylinders (these are the pistons).
• All the pistons should be sticking out equally from the caliper body.
  • It may be hard to see the pistons. Use a flashlight and prop your bike up to help.
• In the next part of the process, you'll be depressing each piston into the piston body to reset it.
  • Keep your hand on the brake lever and look at the pistons. Slightly squeeze the brake lever until one of the pistons pops out further than the others.
    • DO NOT FULLY DEPRESS THE BRAKE LEVER AT FIRST! Your pistons may pop out of the caliper body and brake fluid will spill, requiring a full brake flush.
  • Clean the edges of the piston with a soft cloth.
  • Wrap the end of a large, dull flathead screwdriver or strong plastic pry tool in a soft cloth.
  • Insert the tool and pry the piston that popped out further than the rest into the caliper body.
  • Hold the piston you just depressed in place and slightly squeeze the brake lever until the next piston pops out further than the rest.
  • Clean the edges of the piston with a soft cloth.
  • Use your tool to depress this piston into the caliper body.
  • Repeat this process, holding each previous piston in place to pop out the next piston. Clean each piston before fully depressing it back into the caliper body. You may be able to use a spacer such as a large nut or other tool to prevent the cleaned pistons from popping out again.
• Once all the pistons have been popped out, cleaned, and reset, reassemble everything.
• You may need to squeeze your brake lever multiple times to set calibrate the position of your brake pads with your rotor.