I’ve been working on quite a few disc brake-equipped road bikes in our Praxis workshop lately. One of the problems that keeps coming up is a rubbing or dragging brake.
The type of rubbing I’m seeing can be missed when riding because it’s slight. But if you lift the wheel that’s rubbing off the ground and give it a spin, you’ll realize straight away that the rotor (the metal disc attached to the wheel) is slightly rubbing, because the wheel will stop spinning much more quickly than the other wheel (unless it’s rubbing, too).
I’m not talking about the type of rubbing caused by a bent rotor. That creates a major rub that’s easy to see because the rotor wobbles when the wheel is spinning. A bent rotor will also often make enough noise that you can clearly hear it. To fix rubbing caused by a bent rotor requires straightening the rotor – or replacing it if it is too badly bent to be straightened. A great tool for straightening rotors is Park's Rotor Truing Fork: http://amzn.to/2xPZxpQ.
The type of rubbing I’m explaining how to fix here happens on straight rotors. It’s highly annoying because, while it’s only slightly dragging, it’s constantly slowing you down and wasting your energy. You can try squeezing and releasing the brake lever repeatedly, removing the wheel and reinserting it, gently flexing the rotor to try to push the rubbing pad away – but the brake will usually still rub as soon as you brake again.
Fortunately, there’s a fix for this problem that almost anyone can do. All you need is the right wrench to remove the brake caliper from the frame and an ordinary business card. Don’t worry. You do NOT need to disconnect the brake hose/cable from the brake caliper or change any brake adjustments.
Tip: When working on disc brakes keep all oils (even from your hands), greases, lubes, etc. away from the brake pads and rotors. Lubes can contaminate and ruin the braking. If you make this mistake, to fix it, you’ll probably need to replace the brake pads and super clean the rotors.
To fix the rubbing, follow these 5 easy steps.
- Remove the rubbing caliper from the frame by loosening and removing the two bolts holding the caliper in place (turn the bolts counterclockwise). Before taking the bolts all the way out, be sure to note (take a photo) which one goes where and the order of any parts between the bolt head and the brake caliper. There may be washers or locking washers and one bolt may be different than the other. Be 100% sure you know exactly how the bolts and any parts go back on so you can get it right when you reinstall the caliper.
- Now, hold the removed caliper in your hand. It’s still attached to the brake hose/cable, but there’s room to work on it. Next, fold an ordinary business card in half and slip it inside the caliper as shown in the photo. Then wiggle and push the caliper back over the rotor so that the business card is in between the rotor on both sides and the brake pads, too (they’re tucked inside the brake caliper).
- While keeping the caliper on the rotor, turn the wheel so that the caliper lines up to the bolt holes in the frame. Then, put the bolts back through the caliper, using care to put the bolts in the right place and any washers or tension devices in the right place, too. Refer to your photo. Screw the bolts clockwise until the caliper is loosely mounted back on the frame with the business card still in place inside the caliper.
- Now, squeeze the brake lever and keep it squeezed while tightening both brake caliper bolts fully. If you're working on the rear brake, you might not be able to reach the bolts while holding the brake on. So, ask a friend to help, or wrap something around the brake lever that keeps it firmly squeezed, like a toe strap or strong elastic band. (Tip: Considering buying a Bike Brake for each of your bikes – click to read our review from a few years ago. They're great little rubber band-like devices that you can keep on your handlebar just for instances like this, and use to park your bike almost anywhere just by leaning it against something.)
- Now that the caliper is back on the frame and tight, release the brake lever and squeeze it a couple of times as if braking. Now, turn the wheel while holding onto the edge of the business card and the card will rotate with the rotor and come out. Once the card is out, you should find that your brake works nicely again with no more annoying rubbing!
Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.