Published on May 30th, 2016 | by Greg O'Keeffe
Ask a Mechanic: Eliminating Brake Rub
Lindsey asks, “I’ve been having brake rub on both my road and mountain bikes. Can you show me how to fix the problem for both caliper and disc brakes?”
There are few things that will frustrate a rider more than brake rub. Whether it’s on the road or the trail, the constant tick or scrape is bound to drive you crazy. Luckily, no matter where the issue stems from, it’s usually a quick fix.
Eliminating a brake rub on your road bike is usually quite simple. Assuming your wheel is true, most brake rubs can be fixed in one of two ways. The first way to eliminate a rub is to loosen the brake completely and re-center it. This only needs to be done if the brake is way out of alignment. The easiest way to get it re-centered is to loosen the brake-fastening bolt until the brake moves freely. Once the brake is moving freely, pull the corresponding lever to the brake you’re working on until the pads are in contact with the rim. Once the pads are touching the rim, re-tighten the brake bolt to secure the brake back in place. Be sure to follow the manufacturer’s torque spec when tightening the bolt. Once the brake is secure, release the brake lever and check to make sure that the brake is centered correctly.
The second method of eliminating a rub on a road bike can be used when tolerances are very tight between the pads and the rim. This is more of a fine-tuning adjustment that should get rid of brake rub and make sure that the pads are contacting both sides of the rim at the same time. Most rim brakes have a small screw on top of one of the pivoting arms that can be used to make side-to-side adjustments brake adjustments. Simply rotate the screw using the proper sized Allen wrench to move the brake in the correct direction. The newer SRAM Aero Link brakes require a thin 13mm wrench or cone wrench to center the brake. Then adjust the spring tension on either arm to calibrate when the arms come in contact with the rim. Moving the caliper side-to-side can effect where the pads contact the rim, so you should always check to see if the pads are still contacting the rim on the braking surface after making any adjustments.
When it comes to disc brakes, the initial set up and process for eliminating a rub is very similar to the road brake method. You’ll want to start by loosening the caliper bolts until the caliper moves freely. Once again, you’ll want to pull the lever for the corresponding brake and then tighten the bolts evenly to the manufacturer’s recommended torque values. Doing this will usually work to center the rotor in the caliper and eliminate the rub. If that doesn’t do it, you may have to visually inspect the rotor as it moves through the caliper and make adjustments to one side or the other, manually moving the caliper by hand.
However this doesn’t always do the trick. With disc brakes, the most common cause of a rub is a bent rotor. I can almost guarantee that at some point your rotors will bend and cause a rub. If that’s the case, the only way to fix the problem is to bend it back. Manufacturers recommend using a dedicated rotor-bending tool, but you can use an adjustable crescent wrench in a pinch. Just make sure the tool is free of contaminants by cleaning it with rubbing alcohol before using it. Adjust the wrench down to the thickness of the rotor and you’re ready to start bending it back. To do this you’ll want to spin the wheel while looking at the rotor as it goes through the caliper. As it moves through the caliper, pay attention to where the brake the rotor is making contact with the brake pads.
If it’s a small rub, you may have to put your ear close to the caliper and listen for the rotor to make contact with one of the pads. Once the location of the rub has been identified, rotate the wheel until that section of the rotor is in a spot where you can bend it in the opposite direction of the rub. Work in small increments so you don’t just create a rub on the other side of the brake. This requires a bit of time and patience, depending on how badly the rotor is bent. It may be bent in several places, so eliminate the big bends first and then go after the smaller ones. You might have to mess around with re-aligning the caliper a few times after bending the rotor back to true, as the process may have thrown your caliper off-center.
Follow these procedures and you’ll be back to spinning in silent bliss in no time. Don’t forget to check out artscyclery.com for all your bike maintenance needs.