Replace disc brake pads

Skill level 2 of 4 · Tune-upReplaceBasic20 minMechanical 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 ($$)
Shop rags + nitrile gloves: shop towels and nitrile gloves ($)
Isopropyl alcohol 91%+: isopropyl alcohol 91% ($)
Digital calipers: Clockwise Tools DCLR-0605 IP54 Digital Caliper ($$)

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Steps

Remove the wheel. Wear gloves: skin oil contaminates pads.
Back the inner pad adjuster all the way out.
Remove the pad retaining pin or clip (some pads pull straight out the top or the back with needle-nose pliers).
Note the pad shape and spring. Take the old pad to compare, or check the model stamped on the caliper. Verify your pad shape before ordering (My Bike → Verify). Replace pads with under 1 mm of friction material (pad plus backing plate under 3 mm on SRAM/Avid), and check the rotor is above the minimum stamped on it (usually 1.5 mm; SRAM 1.55 mm).
Fit new pads with the spring between them, refit the pin and clip.
Clean the rotor with isopropyl alcohol on a clean rag.
Refit the wheel, close the QR firmly, then do the Center and adjust guide.
Bed in: stay seated, ride to about 12 mph and brake firmly to walking speed about 20 times without stopping fully, then about 10 harder stops.

Diagram

Looking down from aboveDisc brake caliper (either wheel)

Mechanical disc caliper (one moving pad, top view)

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

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