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How-to guide

E-bike brakes: signs of wear and how to replace disc brake pads

E-bikes are heavier and faster than regular bikes, so brakes need regular checks. How to tell when pads, rotors or fluid need attention, and how to swap disc pads.

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

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Difficulty
Moderate
Time
30 to 60 minutes

Tools

Parts

Bosch reminds riders that e-bikes are heavier and get up to speed faster than regular bikes, so it's worth knowing how your brakes respond and checking them regularly (Bosch owner guide). This guide covers the checks anyone can do and a disc pad swap. Hydraulic bleeds are a separate job, covered at the end.

Two kinds of disc brakes

Mechanical disc brakes are pulled by a cable. Hydraulic disc brakes push fluid through a sealed hose. Hydraulic brakes use either mineral oil or DOT fluid, and Park Tool warns never to put one in a brake designed for the other (Park Tool).

Signs your brakes need work

  • Metal-on-metal grinding when you brake usually means the pads are worn out. Shimano says replace them right away to avoid damaging the rotors (Shimano maintenance tips).
  • Squeal, extra lever effort, or a dark rotor that smears when touched can mean oil or fluid has contaminated the pads (Park Tool).
  • A spongy lever, or one that pulls to the bar, can mean air or contamination in the hose, or a leak (Shimano maintenance tips).
  • Discolored rotors need cleaning or replacing, and a rubbing noise as the wheel spins can mean a bent rotor (Shimano maintenance tips).
  • New bikes can be noisy for the first rides while pads wear in. Lectric puts this at roughly 50 to 100 miles (Lectric).

Step-by-step: check and replace disc brake pads

1Check the levers and the motor cut-off

Squeeze each lever. It should feel firm and stop well short of the bar (Shimano maintenance tips). If your bike has brake sensors, both levers must spring fully back, because a lever that stays pulled keeps the motor cut off (Velotric troubleshooting).

Photo needed: A hand squeezing a brake lever with a clear gap left between the lever and the grip. Add one

2Measure the pad material

Look into the caliper and judge the friction material, not the metal backing plate. Park Tool's general rule is at least 1 mm of pad material. Shimano's dealer manual says its pads must be replaced at 0.5 mm or less (Park Tool, Shimano dealer manual). Go by your brake maker's number.

Photo needed: Looking down into a caliper at two pads, with the pad material and backing plate labeled. Add one

3Check the rotor

Shimano says to replace its rotors when they wear to 1.5 mm thick or the aluminum layer shows (Shimano dealer manual). Look for discoloring or a wobble as the wheel spins (Shimano maintenance tips).

Photo needed: Measuring rotor thickness with a caliper gauge. Add one

4Turn the bike off and remove the wheel

Power off and take the battery out before working near a hub motor's cable (Rad wheel guide). Remove the wheel. On a rear hub motor, follow the wheel steps in our flat tire guide. Don't squeeze a hydraulic lever while the rotor is out, or the pistons can close up (Aventon, Park Tool).

5Take out the old pads

Note how the pads, spring and retaining pin sit. Remove the pin clip if there is one, then the retaining pin, then the pads and spring (Park Tool).

Photo needed: Caliper with the retaining pin and clip removed and the pads sliding out. Add one

6Push the pistons back

On hydraulic brakes, press the pistons evenly back into the caliper with a flat, non-marring tool such as a pad spreader or tire lever. On mechanical brakes, back the pad adjuster off (Park Tool).

Photo needed: A plastic pad spreader pressing both pistons back. Add one

7Fit the new pads

Use pads made for your caliper model. Put the spring in the same way round, press the pads in until they click, refit the pin and its clip, and tighten a threaded pin to the maker's spec (Park Tool).

8Refit the wheel and pump the lever

Refit the wheel with the rotor between the pads. Pump the lever until the pads meet the rotor, then spin the wheel and listen for rub (Park Tool).

9Keep it clean and test it

Keep chain lube, oil and sprays off the rotors and pads. Bosch notes disc brakes are very sensitive to liquids and grease, and Shimano says oily pads must be replaced (Bosch owner guide, Shimano dealer manual). For squeal, Lectric suggests cleaning both sides of each rotor with isopropyl alcohol and a clean rag (Lectric). Test both brakes at walking speed before you ride.

Mechanical disc brakes and pad wear

On Avid mechanical calipers, Park Tool says to take up pad wear with the pad adjusting knobs, not the barrel adjuster at the lever. Using the barrel can let the caliper arm bottom out (Park Tool).

Hydraulic bleeds

A soft lever usually means air in the system (Park Tool). Bleeding needs a kit and the right fluid. Shimano brakes take only Shimano mineral oil (Shimano dealer manual). If that's new to you, a shop can do it, and Bosch lists pad and brake service among dealer jobs (Bosch owner guide).

Sources

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