How to change your rear brake discs & pads

[Parrot of Doom]

Tools required:

2 new discs
Trolley jack or Mercedes jack, 2 tonne axle stands
Wheel brace
16mm ring spanner and 16mm ratchet
Big lump hammer
Pair of adjustable grips/pliers with at least 2 inches clearance
Wire brush and sharp chisel
Copperslip grease
Degreaser
Paper towel
Swear filter

If you've ever changed a wheel, this job isn't that much more difficult than that. Its a pretty simple job, and just requires a bit of brute physical strength.


1) Park the car on level ground, apply the handbrake, put the car in P, turn off the ignition

2) Get your wheel brace out and loosen the bolts to finger-tight levels.

3) Jack the rear of the car up on one side, and put your axle-stand underneath the large rubber jacking point. Let the jack down slightly, and let the axle stand take the strain.

4) Remove the 5 bolts from the wheel, and put the wheel to one side.

5) The next thing we have to do now is remove the calipers.

I is better to retract the pistons at this stage, otherwise the pads may jam on the ridge on the outer edge of the disc. The calipers hold the brake pads in position, and are bolted onto the rear of the wheel hub. It is only possible to remove the pads when the caliper is off, with the exception of cars like the 211 where they have the same double pins as on the front. With this type of caliper you must remove the pads first, by knocking out the 2 pins, then withdraw the pads. To retract the pistons into the body of the caliper, the best way is to undo the bleed nipple, and using a large flat screwdriver between the pad and the disc force the piston back - and then tighten the bleed nipple. It is possible to do this without adjusting the bleed nipple, but its easier not to. Do keep a check on the fluid reservoir under the bonnet so that the brake fluid does not over flow. Don't worry about damaging the disc or the pad as you'll be throwing them away.

At this point, just double check the car is securely raised, since from now on your head is going to be under the vehicle.

Here are the bolts, on the inside of the disc. Some calipers have a different design with 2x 7mm allen bolts behind a rubber plug.

There isn't a lot of room in there, so you'll either need a short socket, or a ring spanner. Either way, the bolts are 16mm. What I do is get my ratchet on the bolts and use that to remove most of the tension. Once they're coming loose, I change over to the spanner as my sockets are too long to unscrew the bolt all the way out. If you have calipers with allen bolts, you may need a bit of pipe or something to extend it to get leverage - a ring spanner is good for this.

You might find it easier with a 11/16ths spanner once the bolt is loose, it makes it easier locating the bolt and helping free it. After a few turns you should be able to unscrew it with your finger and thumb.

Now to remove the caliper from the disc. The bolts are out, but the caliper is stuck fast to the disc.

Just a few light taps to help it free if necessary. Once it moves a little, grab hold of the caliper and work it free. Tap it a few more times if necessary. The pads should be loose now, pull them out.

When the caliper is free of the disc, wedge it somewhere in the suspension behind the hub, or if you can't find a place, just get a tin of paint or something tall, and rest it on that. Try not to let it hang via the brake line. You could also hang it from a piece of wire, or twine.

6) Now to remove the disc.

In normal use, the disc is held on the hub by the wheel bolts. Theres a little allen screw that stops the disc from falling off and breaking your foot. Thats all its there to do, it doesn't have any other function. It won't be tight, so unscrew it and put it to one side.

 

[Parrot of Doom]

At this stage, please be wary of errant cats exploring and scratching your bodywork

Once that screw is off, you'd expect the disc to fall off. Except it won't. It'll be hanging for dear life, and this is where Mr Hammer comes back into play.

At this stage, take the parking brake off and the gear shift out of P making sure that the car cannot move forward or backwards. Next you need back off the parking shoes otherwise the disc may not come off owing to the wear ridge inside the disc (caused by repeated use of the parking brake). Rotate the disc so that the parking brake adjuster is visible through one of the wheel bolt holes (see picture below parking brake adjuster) By putting a thin flat blade screw driver though the wheel bolt hole and rotating the toothed wheel several clicks. ( If it goes tight you are going the wrong way)

I had to belt hell out of mine to get them off, they were stuck fast. You might want ear defenders for this bit. There is a gap in the backing plate where the caliper was, hit the disc here with the hammer, rotating the disc as you go otherwise it can jam. Seriously, you may have to whack the hell out of disc before it will shift, once it starts to move it comes off easily. Be prepared to spend a good few minutes doing this.

7) Once the disc is off, this is what you'll see:

Thats the parking brake mechanism. You can clearly see the shoes, they press against the inside of the disc to hold the car while applied.

Before we put the new disc on, we need to clean all the crap off the surface of the hub:

Give it a right good going over, use the chisel on the stubborn bits near the hub centre. Get every last bit of grime off the surface, and you'll end up with this:

Now is a good time to check and lubricate the parking brake mechanism. The components outside on the rear of the backing plate can be oiled so that they swivel and move easily. Use oil very sparingly inside on the drum components.

 

[Parrot of Doom]

Get your copperslip out, and spray/smear a thin layer on the surface:

This will help prevent the disc from sticking to the hub, and will help make it easier to remove the next time you have to do this job.

8) Now to put the new disc on. The new discs will arrive with a thin layer of either paint, or grease. This is to stop them corroding when on the shelves. We need to remove this.

If its paint, just use the wire brush to scrub it off. If, like mine, its grease, get some degreaser (I used Isopropyl Alcohol spray), and wipe the grease off.

9) Now the new disc is on, we need to set up the parking brake, to do this locate the adjuster again and turn it so that the disc will not rotate, and then apply the parking brake (ensure the gearbox is not in P) now release the parking brake again and turn the disc. If it is tight back off a few notches on the adjuster so that the disc turns freely - a faint rubbing is OK. The parking brake is self adjusting from now on.

Get the allen bolt, and find the smaller hole with the thread (there are 2 small holes, only one is threaded). Then put the new disc onto the hub, line up the holes, and tighten the allen bolt into place. Not too tight, its only to hold the disc in place while the calipers and wheel bolts are off.

Take the new pads and apply a coating of brake pad grease to the back side of the new pads including any metal shims and a little over the face of the piston, and place the pads into the caliper. Slide the caliper complete with pads over the disc an re fit the bolts (the bolt should be replaced with new ones, but its ok to put a little dab of red locking compound on the ends instead).

For bolt tightness I just make sure they're very tight. I usually check them after a few weeks to make doubly sure they aren't coming loose, they never have yet.

Now the disc is on, the calipers are on, all you need to do now is apply a thin layer of copperslip grease to the surface of the disc (not the braking surface).

And thats it. Job done, pop the wheel back on, take the car off the jack, tighten the wheel bolts diagonally (bolt 1, bolt 3, bolt 5, bolt 2, bolt 4), and do the other side.

Once you've done both sides, put your tools away and take it for a drive to test. You'll have to pump the brake pedal a few times when you start the car, but otherwise it should be fine.

The parking brake may feel slightly tighter as well, as the inside of the disc is less worn.

 

[Parrot of Doom]

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