Rubbing disc brakes can be a real drag when you're out on the bike. They feel annoying, they sound annoying, and your riding buddies will probably get fed up and tell you to sort it out. Thankfully Michael has a few tips to share to help make your brakes drag-free again.
There are a few things that might cause your brakes to rub. The issue could be from any one of these or a combination of all of them. In this post we're going to take you through the steps to:
- Reset the pistons in your brake caliper
- Align the brake caliper
- Straighten the wobble out of your brake rotor
Things You'll Need:
- Piston Press Tool or a Screwdriver
- Rotor Alignment Tool or a Shifting Spanner
- Allen Keys
- Mobile Phone
- Isopropyl Alcohol
- Clean rag
Reset the Pistons
The pistons in MTB brake calipers normally do a pretty good job at centering themselves as they extend over time to compensate for pad wear. However, on some brakes one or more of the pistons can be a little over active and end up sticking out further than the others, causing the pad to rub or come in unevenly as you pull the lever. You might be able to feel this as you apply the brake, or see that the rotor gets pushed to the side slightly as the pads come in.
If this is happening you can reset the pistons by gently pressing them back in with a piston press tool or a large screwdriver. This can be done with the pads in or out, but if you do it with the pads in, make sure you only use gentle pressure and that your tools are spotlessly clean so that you don't damage or contaminate your brake pads.
Isopropyl alcohol is the best for this as it’s effective at removing oils and grease and evaporates cleanly without leaving any residue behind. Give your tools a good spray and wipe with it before you begin!
If you press the pistons in with the pads out and don’t have a piston press tool it's a good idea to wrap the screwdriver in a rag first so you don't accidentally damage the pistons. A sturdy plastic tyre lever also works well for this.
Once you've pressed the pistons back in, reinstall the pads and the wheel and give the lever a few squeezes. As you do this the pistons will extend back out and should hopefully clamp the brake rotor evenly on both sides without one piston coming out further than the others.
You might need to repeat this process a couple of times. If one side keeps coming out further than the other the pistons might be dirty and in need of a good clean and lube to get them moving smoothly again.
Park Tool recommends that you clean and lube your brake pistons each time you replace your pads and they have a great video on Youtube that runs through the process in detail.
Align the brake caliper
If the brake caliper isn't set up straight you're pretty much guaranteed to get some degree of brake rub. Thankfully, aligning your caliper can be pretty straightforward if you know a few tricks.
The first thing I like to do is to carefully apply a bit of grease under the heads of the bolts. There is nothing worse than getting everything perfect, only to have it all go wrong and start rubbing again when you go to crank down the bolts at the end.
The grease allows the bolts to torque up smoothly without making the caliper twist or move out of alignment when you snug them up. This will save you a lot of anguish later on!
For starters, let's undo the bolts enough so that the caliper is free to move around slightly, then grab the brake lever, and give it a good squeeze. Hold the lever in while tightening up the bolts ever so gently, alternating between them until they engage just enough to hold the caliper in place.
Sometimes all the stars align at this point and your brakes will be wonderfully drag free when you spin the wheel. If that’s the case you can just torque them up to spec (gently alternating between the two bolts again) and be merrily on your way.
Unfortunately, reality doesn't always work like that so the rest of us have probably still got some work to do!
If the rotor is still rubbing we'll need to visually align the caliper by looking down through the gap between the brake pads and make small adjustments until there is an equal amount of free space showing on either side of the brake rotor.
A white screen on your phone or a piece of white paper can be helpful if you position them on the opposite side of the brake so that you have a bright background to work against.
Loosen one bolt at a time, pinch the brake mount between your fingers, and make really small tweaks to the position of the caliper until you can see even free space on each side of the rotor, or notice that the wheel starts to spin freely. Gently tighten the bolt up again and do the same on the other end of the caliper.
It might take a couple of goes but if you manage to get the wheel spinning freely at this point you can proceed to high-fives and be on your way.
If there is still a bit of rub in one spot or a wobble in the brake rotor it's time to crack out the tools to straighten out any bent sections of your brake rotor.
Straighten the wobble
A rotor alignment tool is perfect for this task but a small shifting spanner also works well. Just be sure to make it squeaky clean with the isopropyl alcohol before it goes anywhere near your brakes!
You'll need a nice quiet environment for this so that you can hear what's going on.
- Slowly spin the wheel and watch the rotor as it goes into the caliper.
- Listen out for any telltale rubbing noises.
- When you notice the rub, stop the wheel and take note of which section of the rotor is next to the brake pads
- Can you tell which way the wobble is going?
You might need to gently rotate the wheel back and forth a few times to hone in on the section that needs attention and work out which way you'll need to tweak it.
Grab your tool, attach it to the rotor and gently apply a bit of pressure in the opposite direction to the wobble. Softly softly is the name of the game here as it's really easy to go too far one way or the other if you're too heavy-handed. You're much better off having to bend it one direction 2-3 times before you nail it rather than having to go back and forth multiple times because you've gone too far.
Hopefully, by this point, you have fully functioning pistons, a perfectly aligned brake caliper, a nice straight rotor, and totally drag free brakes. Your sanity has returned, there’s hero dirt on the trails, and you're free to ride off into the sunset on your blissfully silent bike!
Is your rotor warped beyond repair? Grab yourself a fresh one HERE