How to change your brake discs

Worn discs are an MoT failure, so check yours out today

Feeling a judder? 1

A problem with your brake discs can often be felt as a judder at the brake lever, front or back, as you apply the brakes. This juddering symptom is often the result of a warped disc, caused by wear or damage. Your first step is to check the condition of the discs, so put the bike on stands so the wheels can be spun freely for a visual check.

Highlight cracks 3

Brake discs are prone to developing cracks with age and use, something which can be a particular problem for older bikes. Inspect each disc carefully, rotating the wheel in small increments and use a hand-held torch to ensure you get the best light. A crack can often be difficult to see, so take your time. It may not be as dramatic and obvious as the one here.

Remove the calipers 2

The brake caliper needs to be undone so remove the bolts that secure it to the fork leg. Gently slide the caliper off the disc and secure it to one side with a cable tie or bungee. Repeat with the other side. With the calipers out of the way, spin the wheel and make sure it rotates freely. Never allow the brake caliper to simply hang on its hose.

Feel the thickness 4

Manufacturers often stamp the disc’s minimum thickness somewhere on the disc. This measurement is taken across the pad contact area, and on a badly worn disc the outer edge will be raised like a lip. Don’t rely on feeling for a judder, because worn discs may not always not warp but could still fail in more drastic ways, such as cracking.

Wheel off and safe 5

Remove the front wheel and place it on a suitable, protective surface. At this point make a note of the wheel’s direction. On bikes with ABS there is often a sensor ring that on a twin disc setup goes on one side only. Also keep an eye out for any spacers and which side they are located.

Clean the hub 7

With all of the bolts removed, lift the disc away from the wheel hub. Before you fit the new disc, clean the mating surface thoroughly using a Scotchbrite pad. You’re aiming to remove any rust from the disc or oxidization of the alloy. Finally, use a clean cloth and wipe the surface with a brake cleaner to ensure the area is completely free from muck and grime.

Spin and clean 9

Reinstall the wheel with all the spacers in the correct position and make sure the spindle and pinch bolt tightening sequence is correct, then torque up correctly. Spin the wheel and use clean paper towel and brake cleaner to wipe the new discs, because they are often coated with a greasy anticorrosion compound which needs to be removed before use.

Crack the disc bolts 6

Undo the disc retaining bolts. Start by giving each bolt an 1/8 of a turn, then undo each one in a diagonal pattern. Quite often these bolts are stubborn, so use a good quality Allen socket or single hexagon socket to reduce the potential of slipping. Flip the wheel over and repeat the process.

Get locked in 8

Read any instructions on the packaging relating to new disc installation. Check that the new discs are the same type and diameter as the old and that the bolt holes line up. Fit the disc, then apply a small amount of threadlock to each of the bolts and tighten up evenly in a diagonal pattern. Torque all bolts up to specification.

Refit the calipers and test 10

To give your discs the best possible start, it’s good practice to fit new brake pads at the same time. Make sure pads are the correct type for the model, and that retaining clips and pins are secure. Refit the calipers and torque the bolts up to the recommended spec. Spin the wheel and pump the front brake lever several times until it feels firm.