Our final brake pad replacement guide: disc brakes. Due to their effectiveness in wet conditions disc brakes are finding their way on to more and more bikes, particularly those used for commuting. They are great in London traffic when you have no idea who or what will walk out in front of you next. These kind of brakes will be on many more bikes in the future now the UCI has allowed them on competition bikes as well.
The pads usually need replacing when they reach 1mm of thickness (new pads are usually 3-4mm). It’s tough to judge the remaining thickness of the pads without removing them for a closer look. So this repair will talk you through removing the pads and, if needs be, replacing them.
When performing this repair it is important not to touch the pads or disc rotor because the oils from your fingertips will increase the probability of the brakes making squeaking noises, as well as possibly reducing the stopping power of the brake system. The steps below will indicate what you should do if you do happen to touch either the pad or disc rotor surfaces. You’ll need an Allen key, small flat head screwdriver, small needle nosed pliers, rubbing alcohol and cotton swabs.
First, remove the front or back wheel depending on which pads you will work to replace first. Although not strictly necessary, it is often easier to replace the pads if the caliper is removed from frame of the bike. The caliper is typically held on by two Allen bolts. Removing these bolts allows you to hold the caliper in your hand.
As shown in the graphic above the two pads have a small handle extending up from the caliper. Take note of the orientation of the pads in your caliper, as you’ll want to insure you insert the new ones the same way. Depending on the model of caliper and its overall condition, you may be able to grasp the handle of the inner pad (the one with the bend in the handle) and push it laterally back while pulling up in order to remove the pad. If it proves too difficult for your fingers, try using needle nosed pliers, taking care not to bend the handle or use excessive force.
If needle nosed pliers fail, I find that taking a small flat head screw driver and carefully inserting it behind the pad, into one of the small circular openings (as shown above), and gently prying up, the pad will pop free of the keeper. Note that there is typically a very thin, metal retaining clip (shown below) that you should take care not to lose.
At this point examine the pads to see how much braking material remains. It may be that you can simply clean the pads and reuse them depending on their condition. To clean the pads, use cotton swabs dipped in rubbing alcohol and swab across the face of the pads until the cotton swabs come away clean. You may also want to use the cotton swabs, or a dry rag, to clean the inside of the caliper as well, as mud and dirt can collect there.
Now it is time to reassemble the pads in the retaining clip. Place the outside pad (straight handled) on a flat surface, and lay the retaining clip on it as shown in the picture above. Note how the bend in the retaining clip is between the two clips on the pad. Next slide the inside pad into position in the retaining clip, making sure the bottom clips on the pad align with the outside pad.
Now carefully slide the pad assembly back into the caliper as shown, making sure the pads are oriented as they were when you initially removed them. Push the assembly down into the calliper until it snaps firmly in place.
Now reattach the caliper to the fork or frame of the bike, making sure the connecting bolts are firmly (but not over) tightened. At this point, you may want to clean the rotor with rubbing alcohol and cotton swaps to remove any debris or oils from your hands or the road. Once the caliper is reattached, replace the appropriate wheel.
With the wheel reattached, it is time to adjust the caliper for optimum braking action. Reach through the spokes and loosen (normally counter-clockwise rotation) the inside caliper adjusting knob which has the effect of moving the inside pad further from the rotor. Now, turn it clockwise a turn at a time until the wheel no longer freely rotates without the pad rubbing on the rotor. Now loosen the knob again, by quarter turns until the wheel rotates freely without any rubbing sound from the pad on the rotor. Check your brake handle action and be sure the brake quickly stops the wheel.
Start by removing the wheel. The design of your disc brakes will depend on how the brake pads are held in place. In most designs, this involves a split pin. You should locate the end of the split pin (or two split pins) and pull them out using pliers. It may take a few turns to free to split pins. On other designs the pins are held in place using a bolt. In which case, you’ll need to loosen the bolt to free them. With the spring clip or bolt removed, you can gently pull out the retaining pin.
It should then be possible to push out the pads using a screwdriver. Potentially, you may have a design where the pads are removed from the top instead of dropping from the bottom. Occasionally, the pads will come with a spring retainer. If in doubt, look up the exact model of brakes.
This is again a good opportunity to wipe clean the brake caliper. You should also check to ensure that no fluid has leaked. An old toothbrush or cotton swab can also be very useful for scrubbing away dirt. If there is a spring retainer then it’s worth inspecting to see if it is still springy enough to retract the pads. This is also a good opportunity to inspect the rotor surface. You should only use rubbing alcohol or disk brake cleaner on the rotors.
To refit the pads place them in the spring retainer (if there is one) and push them firmly back into place in the caliper. Some will click into place and others will simply sit in position.
With new pads you may well find there is not a lot of room to manoeuvre the brakes into the caliper. If this is the case carefully use a flathead screwdriver or ideally a pad separator to pry the pistons back into the caliper so there is once again room for the new, thicker pads. Finally, fit the retaining pin and split pin. If you are having difficulty getting the retaining pin back through then the pads are possibly not pushed all the way in or the holes are not lined up.
Re-install your wheel and test the brakes before riding off. Some pads need bedding in more than others, the packaging will advise how to do it – often they need a few sharp stops. It is worth doing this regardless, after some gentle pulls, just to make sure everything is in working order.
Don’t forget to check out our Bike Doctor app if you want more maintenance tips.
What are your tips for replacing disc brake pads?
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As seen on The Guardian, BBC and The Independent.