Repair guides › Brakes
Replace hydraulic disc pads
Disc brake moved by fluid instead of cable: more power, self-adjusting as pads wear. The lever piston pushes fluid that moves pistons on both sides of the caliper.
Open this job in RideLoadout▶ Watch it done
Tools
- Ball-end hex key set (1.5–10 mm): Park Tool HXS-1.2 Professional L-Shaped Hex Set ($$)
- Shop rags + nitrile gloves: shop towels and nitrile gloves ($)
- Isopropyl alcohol 91%+: isopropyl alcohol 91% ($)
- Brake piston/pad spreader: Park Tool PP-1.2 Brake Piston Press ($)
Compare Good, Better and Best for each tool
Steps
- Remove the wheel; never squeeze the lever without a rotor or bleed block in.
- Remove the pad pin and pull pads out. Replace pads with under 1 mm of friction material (pad plus backing plate under 3 mm on SRAM), and a rotor thinner than the minimum stamped on it (usually 1.5 mm; SRAM 1.55 mm).
- Push pistons fully back with the piston press.
- Fit new pads and spring, pin and clip.
- Refit the wheel and close the QR (or torque the thru-axle), clean the rotor with isopropyl alcohol, pump the lever until firm, check for rub, bed in.
Diagram
Cut in half, looking down from aboveDisc brake caliper (either wheel)
Signs it needs doing
- Spongy lever
- Lever pumps up
- Pads drag after a long descent
- Fluid leak