P1020560

This workguide is to demonstrate changing the brake pads on a HR disc brake front end. Pictured above is a set of brake pads ready to go on, these are second-hand but are barely used.

P1020561

The first thing to do before anything else is to loosen the nuts on both front wheels, in the image I have added some numbers to demonstrate the correct order to loosening wheel nuts, you do them in a circular star pattern so that they are released evenly and no one stud/nut is taking all the pressure of holding the wheel. The same goes for re-tightening the wheel, so that the pressure is equal on each stud and the wheel is tightened up evenly.

P1020562

I'll be doing one side at a time so I am putting the jack directly under the shock absorber and lifting there, if you want the whole front end up (to do both sides without having to rejack the car) then you should jack under the center but remember to put a block of wood between the jack and the metal to avoid damaging your car.

P1020563

With the car off the ground make sure to use either some solid wood or jack stands to support the weight of the car, a jack is a lifting tool not a holding tool, they are not safe to hold the whole weight of the car off the ground, especially when your head is underneath it.

P1020564

With the car supported I can now take the wheel off which allows me to get to the caliper and the pads that I need to change.

P1020565

As can be seen in this image the pads are worn well down, the car started to make a slight grinding noise if I braked hard, this was the metal of the pad on the drivers side actually rubbing on the disc rotor, if you keep driving like that it will make a mess of your rotor and you'll be up for a bigger job replacing the rotor as well as the pads.

P1020566

My next step is to take the cap off the brake master cylinder, when putting new pads in you have to push the pistons back into the caliper so if there is less pressure in the master cylinder it will help to push them back, another reason is that since the pads are so low when I push the pistons back for the new pads the fluid level will rise drastically. It'd therefore be a good idea to put a cup or bucket of some sort (or even a rag) under the master cylinder to catch any brake fluid that overflows during pushing the pistons back.

P1020567

The brake pads are very simply held in by two pegs which are in turn held by two split pins or spring wires, to remove the pegs you have to remove the split pin from the peg and then you can slide the peg out, the peg slides through two guide holes in the caliper and through a hole in each of the pads. Once both the pegs are removed there is nothing else holding the pads physically from being removed.

P1020568

Originally these brakes come with a type of spring wire but they are commonly replaced with a standard split pin, when doing this job it is recommended to replace any worn pins like mine pictured above with new ones.

P1020569

This is the peg removed, the peg has a lug at one end to stop it sliding right through one way and a small hole for the split pin to hold it in position, if you should ever need to replace a peg you can simply get a bolt of similar length and diameter and drill a hole in it to do the same job.

P1020570

Pictured I am sliding the pad out of the caliper, sometimes they will stick and you may need to lever some pressure onto the caliper pistons to push them back and give you some room to move the pads.

P1020571

Here I am showing the difference between a set of badly worn pads and a new set, as you can see from the difference between them they originals definitely needed to be replaced. You can also see that from the size of the new pads I will need to lever the pistons back into the calipers to fit them, this is why I removed the brake master cylinder cap earlier.

P1020572

Here again you can see the difference between a new pad and the distance the pistons were pushed out to apply the old pads.

P1020573

Jamming a big screwdriver in there to move the piston back into its bore isn’t the best method of doing it, for one I am putting pressure against the rotor which I don’t really want to do for fear of damaging it, cracking it or even just knocking it out of alignment. The proper tool for the job looks like a large set of pliers, you put it in there and when you push the arms together it pushes the pistons apart. For me though the screwdriver I had laying on the floor of the shed will do, I just take care doing it.

P1020574

As you can see here I have now pushed the pistons back flush with the lip of the bore and they are ready for the new pads to be inserted.

P1020575

Back at the master cylinder we can see how much the fluid level has risen when I pushed the pistons back, there will definitely be a slight overflow when I do the other side, so I will put something to catch it there soon. Pictured in the bottom right is the original fluid level.

P1020576

Not willing to take any chances I have shoved a rag under the master cylinder now before I forget to do it later.

P1020577

I can now slide the new pads into the calipers, make sure you put them the correct way, their steel backing should go to towards the pistons and the padded side toward the rotor, if you get any of the pads wrong the brakes will grind when you apply them (steel on steel grinding) and that can make a hell of a mess of your rotor.

P1020578

With the pads sitting roughly in place I can now push the holding pegs back into position, making sure they go through the calipers and both of the pads.

P1020579

With the pads and pegs in position I have now put the split pins in and the brakes are completely back together and ready to go.

P1020580

While the car is still jacked up is the perfect time to put the wheel back on, if you drop the car on the ground it can become very difficult to add the wheel later. So throw the wheel back on and tighten the nuts up, pictured I have shown how to tighten the wheel nuts in a Star of David pattern which will make sure the wheel comes up evenly and that no one stud is doing all the work. I first bring each of the nuts up lightly, and then go over them again to make them firm and then again to make sure they are tight.

P1020581

Another thing to do before letting the jack down is remove your safety blocks or jack stands; it’s always embarrassing to let the jack down and left to wonder why the car didn’t come down too. I just tell the wife I was making sure the stands are still working properly.

P1020582

After the jack stands are out you can let the car down and get your jack out, if you’ve still got to do the other side then you can now throw you jack under that side and repeat the setup of the first side.

P1020584

With the second side up and disassembled I can now see that this was the side that was causing the problems, if you look closely at the image you can see the lip of the rotor has taken a slight hiding from the metal of the pad that was worn down.

P1020585

This is the pad that was worn, as you can see it was down to the metal.

P1020586

This is the difference between the new pads and the pads that had worn down to the metal; a change was definitely in order.

You can tell when your pads badly need a change by a grating sound from the brakes, this can be the pads worn down to the metal and that metal rubbing on the rotor when you brake.

P1020587

As you can see when I pushed the pistons back on the second set of calipers the brake fluid started to overflow from the master cylinder, the rag caught it all and none flowed over onto any paintwork.