How to maintain AP callipers

Well, the LE front brakes have been causing problems again.

The symptoms to look out for are squealing when driving (goes away when braking or turning), pulling to one side, brakes feel partly on and uneven disk/pad wear.

Look for a wear pattern on the disk that shows the pads aren’t making full contact, like this:





In this case, as the last, it was a build-up of brake dust that was causing the brake pads to seize in the brake callipers.

This isn’t a problem that can be put down to the LE, as it is the same brakes as the rest of the AP shod cars.

You might want to include this as part of your annual service and you shouldn’t have any problems.

First, jack the car up, place on axle stands and remove the wheels



While the calliper is still in place, knock the pins out using a suitable punch and a heavy hammer.



The bottom pin is usually the worst and may need a heavier hammer.

Remove the spring plate, noting that the arrow points downwards in the direction of rotation.



If the pads are free they can slide out at this point. If they are seized then they will have to come out complete with the calliper.

Undo the 2 x 15mm calliper bolts.





And support the calliper on something to take the strain off the flexible hose. You can remove the hose and work on the calliper elsewhere, but you will have to bleed the brakes afterwards if you do this.

Now you can remove the pads. I had to lever them out with a large screw driver, even then it took some doing. Be careful not to damage the rubber boots of the pistons which are behind the pads.



Once removed, you can see the build-up of brake dust around the plates at the end. This is what the pads slide on, so any build-up of dust, dirt or corrosion here will affect the efficiency of your brakes.





Now we need to break up and remove these deposits. I sprayed the area with WD40 as it works well in this situation. Some people may feel uncomfortable using WD40 around brake components, but as long as you avoid getting it on the friction surfaces or rubber boots it won’t cause any problems.



Now use something to agitate the area. I started with a wire brush, but I was concerned that it might damage the rubber boots, so I ended up using a washing up brush and the flat blade of a large screwdriver. Brush and scrape as much dust and corrosion as possible.



Once you have cleaned as much of the deposits off as possible, clean the area with brake cleaner to degrease and remove any remaining WD40.



Now we can turn our attention to the pads. It is easier just to fit new ones, but these have done very few miles so I thought I would just clean up the edges with a file





and added a very thin coat of coppercrest.



Now, push the pistons back as far as they will go (remember the displaced fluid will travel back up to the reservoir and may cause it to overfill), refit the calliper and refit the pads



The pad retaining pins get pretty dirty and corroded too



So either replace them or clean them up with a file or emery paper.



apply a thin smear of coppercrest and refit the pins



remembering to fit the spring plate (with the arrow pointing down).



and hammer the pins all the way in so that the collettes lock into place.

Torque the 15mm calliper bolts up and check the spin of the disk. It should now move more freely. Remember to pump the brake pedal a few times when you have finished both wheels to move the pistons back out (Never do this with the calliper or pads removed). The wheel should still rotate more freely than it did.

Here is a video showing the difference it makes. The first half of the video is after the cleanup and then round to the one I haven’t done yet. They were both seized like this.



Now all you need to do is refit the wheels, take the car off the axle stands and take it for a test drive.

Good luck