In terms of brake friction maintenance, there is a lot more to look out for beyond whether the pads or friction is worn. The surrounding parts should also be checked in any inspection. For our in-depth story on brake friction, we interviewed brake experts from Bendix, Haldex, Hendrickson, Meritor, SAF-Holland, TMD Friction and WABCO. These are the maintenance tips they shared.

For air disc brakes:

• Rotors should be inspected for cracks that extend more than 75% of the rubbing surface and calipers should be monitored for torn or heat-damaged boots and seals. The caliper must also move freely, but not have excessive movement, which may indicate guide pin wear. Look for loose or missing caliper mounting bolts.
• Poor-quality drums or rotors will cause heat to build up at the friction to drum interface, thus it will have a negative effect on the pad life. It may also show up as heat checks or cracks.
• Make sure the cooling vanes are clear of mud and debris.
• When replacing brake pads, inspect the rotors for signs of wear, cracks, grooves, scoring, or hot spots.
• Check the spring brake chambers to make sure the parking springs are not caged in the released position. Be sure the dust plugs are properly installed.
• Make sure that the vent holes in the air brake chamber are not covered with snow, ice, mud, etc.
• Inspect the wheel-bearing unit for grease leaks at every brake pad change.
• Check that all dust caps and boots are present and in good condition.
• After every wheel change, the wheel nuts must be re-tightened to the specified torque level after the initial 100 miles of operation, and then at every regular service interval.
• Check the caliper slide-ability and inspection of the guide pins.
• Inspecting the air chamber for damage, excessive corrosion, air leaks, or the rattle of a broken power spring.

For drum brakes:

• Look for cracked or broken brake brackets/welds.
• Inspect the air chamber for damage, excessive corrosion, air leaks, or the rattle of a broken power spring.
• Verify the brake stroke.
• Inspect for loose cam bushings.
• Measure the ID of the drum for acceptable minimums.
• Grease slack adjusters and cam tubes at required maintenance intervals.