When Disc Brake Pads and Rotors need to be Replaced – and How to Do It!
Now that disc brakes are on all your bikes – road and mountain – the time is now to learn how to tell when your disc brake pads and rotors are worn out and how to replace them. Check out our video and get the nitty-gritty details on how it’s done below.
What You’ll Need
- Measuring Tape
- T25 Torx wrench
- 5 mm Allen wrench
- Flathead screwdriver or Disc Brake Pad Spreader
- Needle Nose Pliers
- Cassette tool (road bike rotors)
- Isopropyl Alcohol
- Clean rag or lint-free cloth
How to Check Disc Brake Pads for Wear
Eventually, the brake pads on your bike will wear out! How often will your pads need to be replaced? That will depend on how often you ride, what the terrain is like where you ride, and what conditions you ride in. Riding in wet/muddy conditions or on steep roads or trails will mean you will need to replace your brake pads more often. You should check your brake pads periodically for wear, here’s how:
- Remove your wheel from the bike. It will be easier to look at the brake pads without the rotor in between them.
- Look down into the caliper to see how much pad remains on the metal backing. Sometimes you can tell right away that your pad is worn out, or it still has enough to get you through the next few rides. If you aren’t sure, remove the brake pads. You’ll need to remove the retaining pin to get the pads out of the caliper. For basic information about parts of the disc brake, how to remove the disc brake pad, and how to remove contamination, check out our guide HERE>
- Measure each brake pad. If there is less than 1mm of pad material, those pads need to be replaced!
- Another reason for replacing disc brake pads is if the pad becomes contaminated with brake fluids, oil or grease.
How to Check Disc Brake Rotors for Wear
Rotors tend to last longer than brake pads, but still should be checked periodically for wear. Here’s how:
- Measure the thickness of an unused part of the rotor (like the center, spider area)
- Measure the thickness of the used edge of the rotor. If the difference is between .2 - .5 mm, then it is time to replace.
- You can also feel if there is significant wear in your rotor by using a paper clip or a pick and running it from the unused portion of the rotor to the used portion. If you can feel a ridge or a step in the surface, then you probably need to replace the rotor.
- Other reasons you could need to replace the rotor include: damaged or severely bent rotor, upgraded/ new size rotor.
How to Replace Disc Brake Pads
When replacing disc brake pads, the first thing to consider is what type of pads you are using. Always replace your pads with the SAME TYPE of pad material, unless you plan on replacing both the pad and the rotor. Pads can be ORGANIC (resin) or METALLIC (sintered). Metallic pads tend to last longer and are a good choice if you are riding steep roads or trails in adverse conditions. Organic pads are very responsive, but they will need to be replaced more often. If you live in an area that is flatter and you ride in mostly dry conditions, organic pads could be a good choice. Also, make sure you purchase pads that are compatible with your caliper. The make and model of your brakes should be listed on the replacement pad packaging. Here’s how to you’ll replace those pads:
- Using a pad spreader or flathead screwdriver, push the pistons back into the caliper. This will make it easier to put the new pads in and prevent them from rubbing the rotor.
- Remove the old pads. You may need a screwdriver or Allen wrench to remove the pin that holds the pads in place.
- Once the pads have been removed, clean the inside of the caliper/pistons with degreaser. This will ensure your pistons are moving properly and not stuck in place. Wipe the caliper clean. You do not want to leave excess degreaser inside the caliper, as it could contaminate the new pads.
- Place the new pads into the caliper, making sure you do not touch them with your fingers. The oils on your fingers can also contaminate the new brake pads.
- Secure the new pads with bolt/pin provided in the package.
How to Replace Disc Brake Rotors
First, check to make sure you have the right replacement rotor and tools for the job. There are two different kinds of rotors: 6-BOLT and CENTER-LOCK. Most newer mountain bikes will come with 6-bolt rotors and road bikes tend to come with center-lock rotors. Here’s how to replace your rotors:
- Remove the old rotor. Use a cassette tool for center-lock and a T-25 Torx wrench for most mountain bike 6-bolt rotors. Your new rotor will likely come with new bolts but retain the old bolts for backup.
- While the rotor is removed, use the opportunity to clean those hard to reach areas of the hub.
- Grab your new rotor. Make sure the arrow is pointing in the direction of the wheel’s rotation before you tighten.
- When tightening the bolts on a 6-bolt rotor, do so in a star pattern.
- When replacing a center-lock rotor, replace the end cap and make the first few rotations by hand to ensure the cap is properly threaded. Then, use a cassette tool to tighten.
- Always make sure you tighten bolts to torque spec indicated by the manufacturer.
- Never use grease or lube on brake rotor bolts. Heat that occurs during heavy breaking could cause grease to seep out and contaminate the rotor and pads.
- The threads of a center-lock rotor end cap and bolts of a 6-bolt rotor should come with pre-applied thread lock. If there is none, apply a single drop of thread lock to each bolt hole and wipe away excess.
- It’s always a good idea to use Isopropyl alcohol to remove any contamination from the new rotor before replacing the wheel.
- Replace the wheel and check to make sure the caliper is properly aligned (no brake rub). If there is brake rub, use our guide on how to fix squeaky disc brakes to realign your caliper!
How to Bed-In Disc Brakes
All disc brake pads and rotors need to be “bedded-in” or pre-worn before your first ride. This prevents excessive noise and will ensure even and predictable braking. Basically, your goal is to heat up the pads and rotors, depositing an even layer of pad material onto the rotor (or braking surface). Here is how to do it:
- Find a vacant parking lot or quiet neighborhood street where you can ride safely.
- While seated on your bike, accelerate to a moderate speed.
- Apply both the brakes firmly and evenly but DO NOT come to a complete stop. Let off the brakes gradually.
- Repeat this process 15-30 times until you feel the brakes biting with more power.
- Let your brakes cool down before your first ride.