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!
This is the right way to do it. Beware of mechanics that will just spray brake cleaner in between the pads and rotors and say ‘fixed’. Since you will more than likely pay a couple of dollars for a mechanic to look at your brakes, make them do it right. I highly recommend to print out Jim’s article and take it with you!
I often find disc brake squeeling is related to a slight bend in the rotor. My mechanic uses a plier-like tool to make micro-adjustments in the disc which fixes the noise. I haven’t been brave enough to do this yet. How about an instructional on this?
Thanks!
If I was a mechanic and you brought an article in telling me how to do my job, I’d most likely throw you out! If your mechanic doesn’t know how to perform this simple task you either need to find a new mechanic or learn to do it your self. Do not take instructions to a mechanic!
I don’t know if this is true of all disc brake systems, but with most be careful you don’t squeeze the brake lever while the wheel is out. This can drive the brake pistons out too far and then you’ll have to carefully push them back in. Special tools are made for brake pistons but if you search online you’ll find you can use a large screwdriver or something similar if you are very careful. Rule of thumb though, if the rotor is out of the brake, don’t squeeze the lever.
Jim, a frustrating problem I have is on our road recumbent tandem I get no rub on the stand or trainer but when riding I get a rotor rub. Sometimes a quick squeeze of the brake handle makes it go away most of the time it doesn’t. Yet when I get this rub I can immediately get off the bike lift the wheel off the ground, spin it, no rub. Ideas? Thanks! – Greg
[quote=Dave Minden]I often find disc brake squeeling is related to a slight bend in the rotor. My mechanic uses a plier-like tool to make micro-adjustments in the disc which fixes the noise. I haven’t been brave enough to do this yet. How about an instructional on this?
Thanks![/quote]
Thanks for the suggestion, Dave! I’ll write a Tech Talk about truing rotors sometime soon as a follow-up. Thank you.
That’s good advise, Jeff, thanks.
I generally find that the solution is to slacken the bolts to the piston, squeeze and hold the brake on and re-tighten the bolts. Job done without any dis-assembly!
If you have mechanical disc brakes, Greg, it might be that something is changing when your weight is on the bike that’s acting to apply the brake. This can happen with all cable brakes. A common example is with rear brake cables on road bikes. When the brake adjustment is too tight and you turn the handlebars to the side, it tightens/applies the rear brake. The solution is to put a little more slack in the cable so there’s more leeway to counteract the tendency of the bike to apply the brake.
If you’re lucky that’ll work, Henry. But on a lot of disc brake bikes that won’t be enough to do the trick because the frame braze ons that the caliper is screwed into aren’t perfectly aligned with the rotor. So the business card trick is a nice one to keep up your sleeve for when you run into this. The reason it works is because it forces the spacing between the pads and rotor instead of relying on the frame’s braze ons to hold the brake in the right place. But I’m glad your bike is so cooperative.
Why not loosen the caliper nuts without removing them, remove the wheel, put the folded card over the disc and reinstall the wheel with the card? Then you don’t have to worry about pieces and parts getting out of place.
[quote=Will Haltiwanger]Why not loosen the caliper nuts without removing them, remove the wheel, put the folded card over the disc and reinstall the wheel with the card? Then you don’t have to worry about pieces and parts getting out of place.[/quote] That’s another way to do it that can work, Will. Thanks. The only thing is that it can be tricky on some bikes to get the rotor back into the brake caliper when the business card is on it – and to keep the business card in the right place on the rotor so that the card ends up exactly between all 3 things (rotor and both pads). You can do it if you’re patient and careful but if you’re not, you could get the card in the wrong place or even knock a pad loose. In comparison, when you push the caliper over the disc you can see what you’re doing, the card will stay were you put it inside the caliper and it’s less likely you will damage anything. But, your approach will work fine and can be a quicker, better way to do it, as long as you work carefully. Thanks! Jim