The objective in this guide is to eliminate the grinding and/or scraping sounds associated with rubbing and contaminated Disc Braking Systems.
Part One – Removal of the brake components.
The first step is to open the quick release cam lever and undo the nut on the end of the wheel skewer, then to completely remove the wheel from the frame/fork. [Fig.1a]
After the brake rotor is free of the caliper, proceed to unscrew the (2x M5) Hex fasteners that secure the caliper to the frame/fork [Fig.1b]
- Once the caliper unit is free, proceed to remove the (2) brake pads from the housing. For most mechanical systems – this is a simple case of pulling the pads off the piston, which is secured by a magnet. For hydraulic systems, there is most likely a small yet long fastener or split pin that needs to be removed before the pads can be pulled free. [Fig.1c & 1d]
Part Two – Cleaning of the brake pads.
Now that the pads are free, notice the dark etchings and braking tracks on the surface [Fig.2a] – this is what we are going to remove. Using the disc brake cleaner aerosol and a piece of 220grit emery cloth, first spray the cleaner onto the pad [Fig.2b] and then work the cloth in a circular motion [Fig.2c] until the lighter, original pad surface begins to show through. [Fig.2d/2e]
Part Three – Reassembly.
Now that the pads are clean, proceed to reinsert them back into the brake caliper by simply reversing the method used to remove them. Some brake pads are not left and right specific (most round pads) but some systems (the more rectangular pads) require you to have them orientated a certain way i.e. the clip that connects the pad to the caliper might not be exactly in the center of the pad, and will need to be on a certain side of the housing to be installed correctly. If you take note what the shape/orientation of the caliper housing is, you can use this as reference to find out which side is which for the pads. [Fig.3a]
Once the brake pads are in the caliper, you can now re-attach the caliper to the frame/fork using the (2xM5) fasteners [Fig.3b]. At this point, do not tighten the fasteners all the way – but leave some play in the caliper, as we need it loose for a later process, which is centering.
Part Four – Inspection, Truing & cleaning of the brake rotor.
The brake rotor is a steel disc, and being made of steel makes it somewhat malleable. If you either position yourself behind the rotor or remove the (6x T25) Torx fasteners and place the rotor on a flat surface, you might find that there is distortion or warping in the rotor causing it to rub on the brake pads. The easiest way to straighten or ‘true’ the rotor is to place the wheel back into the frame/fork and spin the wheel. With the caliper loose, you will notice where there is a left or right warp in the rotor because it will move the caliper in the said direction. [Fig4a] If you use a fork, small adjustable wrench or needle nose pliers you can bend the rotor in the opposite direction to the warp and bring it back into line. [Fig4b] Be very careful and small in your bends, as it won’t take much force to bend a steel rotor. Work in small sections and keep spinning the rotor after every adjustment to see how your progress is going. The rotor doesn’t have to be perfect…but the closer to straight the better.
When you're happy with the rotor being straight, remove the wheel again and place it on a flat surface. Lightly spray the rotor with brake cleaner [Fig.4c] and once again use the emery cloth to score and remove previous brake pad markings from the rotor surface. [Fig.4d] You do not have to stay in line with the metal grain, just make sure that there are no brake tracks on the rotor when completed.
Part Five – Centering the brake caliper and adjusting lever actuation.
This is the trickiest part of the brake setup, the objective is to have the straightened brake rotor in the center of the caliper, with equal space between the left and right brake pads. Sounds simple…but can be a tricky process! Depending of your style of brake – there will be a certain way to orientate the caliper.
For Mechanical Brakes (that use a steel cable)- You want to first grab the brake lever and actuate the brake. The caliper (still loose remember) will automatically center itself against the rotor – but to one side more than the other. Tighten down the (2xM5) caliper fasteners and let go of the brake lever, you will notice that the rotor is not centered but more to the right. [Fig.5a] This is because the mechanical disc brake only has one piston & pad moving upon actuation. The left side of the caliper pushes across, hits the rotor and then proceeds to follow through until the rotor hits the right side pad. If you look at the left side of the caliper, there is a center grub screw (usually a M5 or M4 hex) [Fig.5b] that controls the right pad’s position in the caliper. Clockwise will bring the right pad further in towards the rotor, anti-clockwise will bring it back into the housing and away from the rotor. Using the grub screw, bring the pad back until there is equal space on both sides of the rotor. [Fig.5c]
For Hydraulic Brakes (oil filled systems)- You want to first grab the brake lever and actuate the brake. The caliper (still loose remember) will automatically center itself against the rotor. If you tighten down the (2xM5) caliper fasteners and let go of the lever, now inspect the rotor’s position in the caliper- it should be pretty centered. This is usually easier than a mechanical system because there are two pistons in a hydraulic caliper, and they both actuate at the same time and rate…causing the pads & caliper to center itself automatically. It might take a few attempts to be perfect, and spinning the wheel before you grab the lever can help too. [Fig.5c]
On a hydraulic setup, once centered, a few pumps of the lever will bring the pistons out and will give good lever pull (<1” of throw). For Mechanical systems however, you might notice that bringing the pads in have caused the brake lever to pull back towards the handlebar – to rectify this we have to equally bring both pads back out towards the rotor. The left pad (actuating piston) is controlled by the steel wire anchored on the arm with a M5 fastener and a small cable adjuster barrel, where the brake cable housing meets the lever arm. The right side is controlled by – you guessed it…the grub screw. You can either undo the anchor fastener on the arm and pull some cable through (if a lot is needed) or simply turn the barrel adjuster accordingly and watch as the left brake pad magically moves closer to the rotor. Then do the same with the right side pad until the brake lever pulls the right amount (<1” of throw). [Fig.5d]
The brakes are clean and a new surface on the pads & rotor. Now the easy part, bedding in the new surface. Take the bike out for a few rides around the block, accelerating and grabbing the brake hard to transfer some of the fresh pad surface over to the rotor, there will be some chirping, but this should eventually fade away as the transfer is completed. Then your brakes will feel noticeably stronger and hopefully…a lot quieter. If there is still a lot of noise, there could be chance of either hydraulic fluid through the whole brake pad (In which case a new set of pads is required) or the rotor is still warped and needs to be replaced with a fresh one.