Maintenance Monday: How to Straighten Disc Brake Rotors

Written by: Rémy Rossi | December 23, 2024 | Time to read 3 min

Disc brake rotors can get bent all out of whack, but it’s fixable at home. Learn the simple steps below— we’ve even got a how-to video for some hands-on e-Bike help.

More about the Author: Remy Rossi

Rémy Rossi is a bike writer, mechanic, and educator who got his start in community-based bike shops and co-ops. With a decade in the industry, he still wrenches on bikes when he can and plays bike polo on a fixie.

Disc brakes rubbing? Hearing a squeak or a squeal? You may have a bent disc brake rotor (it’s that circular piece of metal at the center of your wheel). Straightening the rotor will likely solve the problem and get you back to riding noise-free. This maintenance task is doable at home if you have an adjustable wrench and follow these straightforward steps.

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Table of Contents

Introduction

Step 1: Don't panic

Step 2: Diagnose the issue

Step 3: Straighten the rotor

Step 4: Am I done yet?

Key Takeaways

Step 1: Don’t panic

Take it from Colin, our Senior Mechanic at Upway, that rubbing disc brakes is no need to stress. A bit of noise coming from the brake area is quite normal, especially when the disc brake pads or rotors are new. The brake system works via very tight tolerances (we’re talking fractions of a millimeter) and sometimes it just requires some riding to set things into their proper places. If it’s a new e-Bike or newer brakes, continue riding it for a week or two and the slight noise will likely disappear on its own.

If you know you’ve got a bigger problem, however, hop on down to Step 2.

Step 2: Diagnose the issue

First, put your bike in a stand or lift up the wheel so it can spin freely. Give the wheel a spin and listen for a scraping noise (that’s the rotor touching the brake pad) or watch to see if the wheel comes to a stop too quickly. You’re testing to see if the rotor is “true”, or straight enough so it doesn’t bend toward the brake pads. If there’s just a light ding or soft noise, that will probably go away after some more riding as the parts settle in and a bit of brake pad material wears away.

Bike wheels should spin freely for quite a long time before coming to a natural stop. But if you notice that the brake rubbing is severe, you may have a bent disc rotor that’s out of true. The rotor may be making contact with the pad almost the entire time. Or you’ll notice that the rotor hits the pads at a single point in the wheel rotation— that’s where the rotor is most bent.

Focus shot on bike carbon fork and hydraulic disc brakes

Rotor material

One thing to keep in mind is that some disc brake rotors are easier to work on than others. Some rotors are made entirely out of steel (they’ll be completely silver in color) which are easier to work with and a bit more forgiving for home mechanics.

There are also rotors with an aluminum center core and a steel outside which is more flexible and trickier to work with— these are typically installed on performance-oriented bikes or road e-Bikes. My gravel e-Bike, for example, has these nice yet finicky rotors and it took me some time to straighten my rotor out. It’s quite easy to end up creating more problems than you started with working on these types of lightweight rotors.

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Step 3: Straighten the rotor

If you’re up to the task, you can straighten the rotor by using an adjustable wrench. There is also a dedicated disc rotor tool (called a truing fork), but we bike mechanics are normally the only gear geeks who have them. The adjustable wrench is much better than pliers, for example, because of its long straight sides that will leverage or bend the rotor without chewing into it.

Take a look at the pad and rotor from above to see which way the rotor is bent. If there’s no space between the rotor and pad, you’re going to want to bend the rotor away from where it’s touching. Grab the rotor when the wrench is at the point where it’s most bent toward to pad and bend the rotor. Give the wheel another spin and see how you did— this process typically takes a bit of repeating as you gradually straighten out the rotor. Keep making tiny adjustments until the wheel spins freely and isn’t rubbing.

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Step 4: Am I done yet?

If you’ve achieved a freely spinning, noise-free wheel, you’re all set! You’ve successfully trued the disc rotor and it’s sufficiently straight. If there are still slight noises, those will probably go away after a bit more riding. If the issue doesn’t improve, however, come on into a bike shop and the mechanics will take care of you. I’m here to motivate you to do some do-it-yourself electric bike maintenance, but you don’t need to overdo it if you’re out of your depth— your local shop’s mechanics will be happy to see you!

Luckily for you, there’s a hands-on tutorial from Upway’s very own Colin, our Senior Mechanic! He’ll show you exactly how it’s done. Learn expert tips and tricks to quickly fix warped rotors and get your e-Bike back to smooth and safe braking in no time:

And if you need help tightening the brakes on your used electric bike, I’ve got this guide on how to adjust e-Bike brakes. A bit of maintenance know-how and elbow grease builds in a bit of e-Bike insurance when mechanical issues arise so you can get back to riding in no time.

Key Takeaways

Diagnose the Issue: Check for scraping sounds or uneven wheel spinning to confirm a bent rotor.
DIY Fix: Use an adjustable wrench to carefully straighten the rotor until the wheel spins freely.
Know Your Rotor: Steel rotors are easier to fix; performance rotors may need professional help.

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Maintenance Monday: How to Straighten Disc Brake Rotors

Step 1: Don’t panic