Do the friction plates need to be replaced?
Judging by remaining thickness/wear amount (the primary criterion)
The friction material must be replaced when the remaining thickness is ≤2–3 mm.
Typical new pad friction material is about 8 to 10 mm thick, and replacement is required when it has worn down to two-thirds of its original thickness.
If the pad has a wear indicator groove, replace it immediately when the friction material wears down to the bottom of the groove.
When measuring, use a caliper to take 3 to 4 points evenly around the circumference of the gasket, avoiding local deep grooves, and determine the minimum value.
Judging by abnormal retraction distance
The QP brake features automatic wear compensation, with a normal release clearance of typically 0.5 to 1 mm on one side. If the opening and closing travel of the brake arm is noticeably increased (e.g., total travel exceeds 6–8 mm and cannot be reset via the adjustment rod), this usually indicates severe wear of the friction material and that compensation is nearing its limit; thickness inspection is required.
Judging by Appearance and Braking Performance Symptoms
It is recommended to replace or repair regardless of thickness in the following cases:
Large-scale delamination, deep cracks, and charring or carbonization (blackening) appear on the friction surface.
Friction materials contaminated or soaked by grease or hydraulic oil (which may reduce the coefficient of friction and even cause slipping).
A sharp metallic scraping noise occurs during braking (indicating the backplate is about to contact the brake disc), or there is a noticeable reduction in braking torque and prolonged brake engagement time.
If the uneven wear on both sides of the pad exceeds 1 mm, first check whether the caliper slide pin is stuck before deciding whether to replace it.
Friction plate replacement procedure
Turn the manual release screw (or temporarily allow slight air pressure) to open the caliper arms, ensuring sufficient clearance between the brake pads and the rotor.
Locate the spring wire or retaining clip on both sides of the U-shaped groove of the brake block (shoe), and remove it using pliers by pulling or prying it out.
Remove the old friction block from the U-shaped groove in a direction parallel to the brake disc. Repeat the same procedure on the other side.
Confirm that the new pad model matches QP12.7 and that the friction material thickness meets the requirements.
Insert the new friction block into the U-shaped groove of the brake arm and align it with the positioning holes.
Insert and secure the spring wire/circlip, then gently shake by hand to ensure it is tight and not misaligned.
Since the new disc is significantly thicker than the old one, the automatic compensation ratchet/adjustment screw must be rotated in reverse (typically by turning the adjustment knob or screw counterclockwise) to retract the friction pads back to the standard initial position, ensuring a single-side release clearance of approximately 0.5 to 1.0 mm.
Apply 5 to 7 bar of air pressure to release the brake and check whether the gaps on both sides are uniform and symmetrical.
Adjust the clearance adjustment rod/nut as needed, and tighten the locknut to prevent loosening.
Perform multiple no-load tests of the "air release-brake release" and "air cutoff-brake engagement" operations, confirm there are no abnormal noises or dragging friction, then resume operation.
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Phone Number
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