Repair guides › Brakes
Center and adjust mechanical disc brake
A caliper on the fork and frame that squeezes pads against a steel rotor when you pull the cable. Most budget mechanical calipers (Logan, Tektro, Promax and similar) are single-sided: the cable turns an arm that pushes the outer pad, which flexes the rotor slightly onto the fixed inner pad. The inner pad has a dial or bolt to move it closer as pads wear. The caliper position on its mounting bolts sets the alignment.
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Tools
- Ball-end hex key set (1.5–10 mm): Park Tool HXS-1.2 Professional L-Shaped Hex Set ($$)
- JIS #2 screwdriver: Vessel Megadora JIS screwdriver #2 ($)
- 1/4" click torque wrench (about 2–17 Nm) + bits: Pro Bike Tool 1/4 inch drive click torque wrench set (2.2–16.9 Nm) ($$)
Compare Good, Better and Best for each tool
Steps
- Spin the wheel and listen. Tick-tick once per turn = bent rotor (true it). Constant rub = alignment.
- Turn the inner (fixed) pad adjuster until the inner pad just touches the rotor.
- Loosen the two caliper mount bolts just enough that the caliper can slide.
- Squeeze and hold the brake lever hard. This centers the caliper on the rotor.
- While holding the lever, tighten the mount bolts alternately, a little at a time, so the caliper does not twist.
- Back the inner pad adjuster out a quarter to a half turn until the rotor spins free with a hair of gap (paper thickness).
- Use the barrel adjuster at the caliper or lever to set the outer pad close without rubbing. The lever should bite at about one-third of its travel.
- Spin and squeeze. Repeat small adjustments until it is quiet and firm.
Torque
| Fastener | Torque |
|---|---|
| Caliper mount bolts | 6–8 Nm (Shimano/Tektro) · Avid/SRAM 9–10 Nm |
| Cable anchor bolt | 6–8 Nm |
Diagram
Looking down from aboveDisc brake caliper (either wheel)
Signs it needs doing
- Rub or tick each wheel revolution (rotor bent or caliper misaligned)
- Lever pulls to the bar (pads worn or cable stretched)
- Squeal (contaminated pads or loose caliper)
- Grinding metal (pads worn to the backing plate: stop now)
Problems this fixes
- Brakes squeal or howl
- Brake rubs or scrapes when the wheel spins
- Brakes feel weak
- Brake lever pulls all the way to the handlebar
- Rattles over bumps