Brakes can be a real drag, literally. Over time, the hydraulic pistons that were once snappy and responsive can become sticky and sluggish, resulting in everything from noise to brake drag to uneven pad wear. If you’re one of the millions of riders who has suffered from this condition, we can offer some help. There is a quick and easy procedure that can breathe new life into those tired old stoppers, and it doesn’t even require a bleed, any special tools or even much time. It’s called the “brake reset.” This, according to the Shimano multi-service crew, is the most common repair they do for riders and racers when they’re at an event. We can teach you how to do it by yourself.
• 5-millimeter Allen wrench
• 3-millimeter Allen wrench
• Plastic tire lever
• Isopropyl alcohol
• Handful of Q-tips
• Brake-pad spacing chip (specific to your make/model of brake)
• Rotor truing tool, or crescent wrench in a pinch
1-If you have a repair stand, start by putting your bike in with the drivetrain facing in. Normally, this is the wrong way to put the bike in a repair stand; however, if you’re only working on the brakes, this orientation allows much easier access to them.
2-Remove the wheels from the frame. It’s best to work on just one brake at a time, but removing both wheels will prevent your work stand from becoming unbalanced and toppling over.
3-Remove the retainer pin, pads and H-spring from the caliper. This Shimano XT brake required a 3-millimeter Allen to remove the retainer pin.
4-With the pads removed, use the plastic tire lever to hold one piston back and pump the lever a few times.
5-Pumping the lever will expose one piston slightly. Do not pump too much, as the piston can be pushed out too far. Three to five millimeters exposed should be perfect for most brakes. With the one piston now exposed, it’s time to clean the surfaces that seal the brake from brake dust, dirt, grime and debris.
6-Use the spray bottle of isopropyl alcohol to wet the Q-tip, and liberally spray down the caliper and pistons.
7-Use the Q-tip to scrub the outside of the piston surface. Putting the alcohol in a spray bottle makes this easier, but just dipping the Q-tip in works well too.
8-With the inside and outside of the brake now clean, it’s time to lubricate the piston surface. With Shimano brakes, you should use Shimano-brand mineral oil. Just a couple of drops applied directly on the exposed piston is perfect. Never use any lubricant that’s not specified by the manufacturer for this. Shimano recommends using a few drops of their mineral oil, while other manufacturers recommend continuing to move the pistons and allowing the system to lubricate itself. Using lubricants other than those specified, such as chain lube or fork oil, will cause seal problems, pad contamination and a host of other problems.
9-Use the plastic tirelever to push the clean piston back into place. Sometimes, using the body of the caliper for leverage with the tire lever can be useful. Then, repeat with the opposite-side piston. Extract the piston using the tire lever and pumping process, then clean with a fresh isopropyl-soaked Q-tip.
10-Once cleaned and lubed, check to see that the pistons are extending equally by pumping the brakes one to two times without the pads, wheel or rotor in. If they look like this, with an equal amount of piston showing after the couple of pumps, you’re ready to re-assemble.
11-Spray a clean paper towel with isopropyl alcohol to clean the brake. Many shop rags can be contaminated with oils, even if they have been washed, so a paper towel is best for this job.
12-Use the paper towel to thoroughly clean all the surfaces of the brake. We prefer this handy “flossing” tech- nique for cleaning the inside of the brake, which is likely coated with the lubricating oil you just applied.
13-Before reinstalling your pads, measure their thickness. Anything less than a millimeter of pad material, in addition to the backing plate, and it’s time for fresh ones.
14-Double-check that all surfaces in and around the brake caliper are clean. Frames and brake adapters love to hide small pools of fluids that can instantly contaminate pads. Once everything is clean, it’s time to reinstall the pads.
15-The best method for putting the pads back in is to make a “spring sandwich.” That means you should position the H-spring between the pads and then squish everything together.
16-Once you have your brake-pad spring sandwich, slide the pads back into place.
17-Most brake manufacturers make a plastic pad spacer chip that’s designed to perfectly space the pads before the rotor is installed. These typically come with new brakes, but can also be found at the local bike shop. Ask your favorite shop mechanic for one for your model of brake and add it to your toolbox.
18-Don’t forget to reinstall the pad retention pin and torque it properly. Failure to do this can result in your pads flying out mid-ride and could cause a nasty crash.
19-Snap the brake-pad spacer into place. Most of these will stay in place on their own and are designed to help you find the correct pad spacing.
20-Loosen the brake-caliper mounting bolts. If your frame uses an adapter, you should not loosen those. Only loosen the ones that come in from the top and control the alignment of the caliper.
21-Reinstall the wheels on the bike. You should be sure that the rotor is clean before doing this. If there is any doubt, clean the rotor with isopropyl alcohol and a fresh paper towel first.
22-With the brake applied, tighten the caliper mounting bolts. It’s helpful to alternate between the two bolts as you’re tightening them. Tighten the first bolt about halfway, then the other, then finish torquing the first, then the second. This prevents the caliper from moving while the bolts are being tightened.
23-If the squeeze-and-tighten method doesn’t work, use the window on top of the brake to check the alignment of the brake and the trueness of the rotors. You should be able to see a bit of daylight between both sides of the rotor and the pads. Spin the wheel to ensure this is true all the way around the rotor.
24-If your rotor is slightly off—and most are—you can use a rotor truing tool, like this one from Wolf Tooth Components, to bring it back to true. Gently work the rotor in the direction it needs to go. This can also be done with a small crescent wrench—just be sure it’s free of contaminants before throwing it on the rotor.