Everything you need to consider when your disc brake pads need replacing.
If your bike is not braking efficiently or making funky noises when braking, it probably means your brakes pads are worn out or contaminated and need replacing. In this blog post we're going to give you a step-by-step guide on how to replace your disc brake pads to get you back on the road as quickly as possible. And of course, Nic's your go-to guy for advice here too.
1. What you need.
In order to replace your disc brake pads, depending on the brand you will need:
- either need a 2.5 or 3mm hex hey or a flat head screw driver
- needle nose pliers for the retainer pin
- disc brake cleaner or isopropyl alcohol
- a paper towel or lint free rag
- a digital caliber or ruler to gauge the wear of the disc pads
- a piston separator (in most cases we would opt for a plastic tire lever)
- a brake fluid funnel (or syringe for SRAM riders) – not entirely necessary but great to have
- and lastly new brake pads that are compatible with your rotors and calipers. The best way to check this would be to remove the pads and then either take them to your local bike shop or look at the code on them and search for them online.
Most brake pads online will usually state with which model or series they are compatible with. Also note that brake pads are available in different materials including organic (resin), semi-metallic and metallic. They will differ in terms of braking performance, noise, heat dissipation etc. Some brake rotors are only compatible with certain materials so make sure to double check that as well.
2. When and how to remove your disc brake pads.
For most models, when the brake pad material has worn down to about 0.5 mm or if it has gotten contaminated with oils, then it is time to replace the pads. You can check this visually from above and roughly gauge how much material there is left. The best way to check is to take them out and check the thickness using a digital caliper. To remove the brakes pads, you will first need to remove the wheel. Then get out your needle nose pliers and remove the retaining clip on the one end of the retaining bolt. Make sure you don't lose it!
Then remove the retaining pin using the appropriate hex key or flat head screw driver and set the bolt aside. The new pads will usually come with a new pin and clip but in case they don't, you can reuse the old ones.
Now, from the non-rotor side you can simply slide out the old brake pads. At this point you can double check the pad wear and also find the code on the back of the brake pad. From this point on, make sure to not press the brake levers, as that will push your pistons out.
3. Cleaning and resetting the pistons.
Before we put in the new brake pads we need to clean and reset the brake caliper pistons. The pistons are what push the brake pads against the rotor. Over time, as the brake pad wears, the pistons will extend out further to compensate for the wear. Therefore they need to be pushed back in so there is enough space for the new pad.
Before you push them back in, get out your isopropyl alcohol or brake cleaner. Pour some on a paper towel and then feed it through the caliper to wipe off any grime on the pistons. This step is not always necessary, but it is good practice: When pushing the pistons back, it will force fluid up to the reservoir chamber in the lever, create pressure and potentially damage it, especially if there is too much fluid in the hydraulic line. To avoid this, go ahead and open up the lever cap bolt (make sure the lever cap is parallel to the ground so that no fluid drips out), then screw on the bleed funnel or syringe.
If you have some on hand, pour in a bit of brake fluid into the funnel. If you do not have a funnel, then just wrap a paper towel around the lever to catch any oil that might come out. Now, take out your plastic tire lever and carefully, but also firmly and evenly push back the pistons on each side, so that they are flush with the caliper wall. Don't push too quickly, because then the fluid will just spray out. Once they are fully backed up, we can move on to the next step.
4. Installing the new brake pads.
Now you can get out your new pads, making sure to only touch them from the back to avoid contamination. Place the return spring between the pads. This will help the pads to return and back off the rotor plate. Then, if they have any, pay attention to the direction indicators marked on the pads (left and right side). Push the pair together and slide them into the calliper body.
Now get out the new retaining pin and clip (or the old ones), feed it through all the holes including the return spring and thread it in using the appropriate tool. Then lastly, put the clip back on. Before you put your wheel back in, give the rotors a wipe with brake cleaner or alcohol to remove any contaminants.
5. Aligning the brakes and doing a quick bleed.
If you had the funnel on, but without fluid inside, or you did not have the funnel on at all, you can now close up the fluid cap bolt. If the funnel is still on, leave it on for now. Then we are going to loosen up the caliper mount bolts, so that we can get it aligned with the brake rotor, as 90% of time it will be out of place when you change the pads.
Now, squeeze the brake lever 5-8 times to set the pistons. If the funnel with fluid is still on, this will also give you a quick brake bleed. If you notice dirty fluid coming out, you will need a full brake bleed in the near future. On the 8th squeeze, hold the lever down and retighten the caliper mount bolts.
The rotor should now be aligned with the pads. When you spin the wheel, it should not rub. If the funnel is still on, go ahead and plug it up and remove it. If the brake lever is still feeling sluggish, this means you will need to bleed you brakes.
6. Bed in the new pads.
Lastly, before going out on a proper ride, you will need to bed in the pads to ensure that they deliver their full braking power. To do this, take your bike outside, bring it up to some speed and then brake firmly about 10 times. Brake until you’re at walking speed, making sure to not come to a full stop. This will get rid of the top layer on the pads and wear them into the the rotors.
And there you have it! Now you are ready to hit the roads and trails with your fresh brake pads. If you don’t want to replace your disc brake pads yourself, just book on of our service checks the next time you buy a bike on buycycle.com. So check out buycycle.com for your perfect bike and stay on the blog a little longer, if you want to learn more about road bikes or all things cycling. Our team's always got your back whenever a question pops up, but until then, we wish you, as always: Happy browsing, happy cycling!