Fitting new rear discs

When you replace or adjust anything to do with the brakes, always work on the front or rear brakes as a pair. Never change the pads or disc on just one wheel, and when you fit new discs always fit new pads at the same time. Remember too that dust from the brakes is harmful. Avoid breathing it!

And ALWAYS support the car on axle stands. Do NOT rely simply on your car jack!

Click to enlarge Click to enlarge A common problem is uneven wear on the pads, especially the inner ones. This leads to a similar effect of the discs as can be seen in these two photos. The inner face of the disc is badly rusted with only a relatively small area being effective.

Click to enlarge The effect on the pads can also be severe. These shown here are not too bad but the uneven wear on the inner pad can be clearly seen. The problem tends to be caused by the caliper not adjusting properly as the pads wear. The design is such that as the pads wear down, the caliper, which holds the pads, is supposed to slide or self-adjust on the guide pins, but invariably this does not always happen.

Disc thickness NEW = 10.00 mm
Disc thickness MIN = 8.00 mm
Thickness variation = 0.015 mm
Run-out limit at 6mm from disc outer edge = 0.05mm

  • Sometimes it can be very difficult to undo the wheel nuts, even more so once the wheels are off the ground. So, while the car is still on the ground, just crack undone the wheel nuts on both wheels.

    Click to enlarge Raise the rear of the car and support it on axle stands. These should be sited under the sub frame members. A piece of solid wood on the top of the stand can help to prevent damage to any underseal. Do NOT be tempted to work under the car while it is only supported on the car jack!

    Click to enlarge Remove cap from Brake Fluid Reservoir and surround it with rags to soak up any excess spillage.

    Click to enlarge Click to enlarge Remove the road wheels, undo and remove the two guide pin bolts that hold the caliper to the carrier.

    Click to enlarge Release the caliper from the disk and tie it up clear of the disk, ensuring that the weight of the caliper is supported and that the hose is not under stress.
    Remove the brake pads from the carrier, making a note as to which side the pad with the bracket fits.

    Click to enlarge Click to enlarge Remove the two bolts that secure the brake carrier to the hub.

    Click to enlarge Click to enlarge Remove the two screws that hold the disc to the drive flange. You may need to use an impact driver to undo these.

    Click to enlarge The brake disc is usually a close fit to the hub, and may need some gentle persuasion to get it to come off. If the disc is to be skimmed, then use a hide or copper mallet, otherwise a hammer will suffice. Tap the disc from behind, rotate it 45 - 60 degrees, and tap it again. Repeat this process until the disc slowly comes off the hub, trying to keep it as square to the axle as possible.


    Click to enlarge Ensure the drive flange is clean, by wire brushing to remove rust, etc. Wipe the flange and new disc clean, removing any dust, oil or grease. Do not use a petroleum based cleaner to clean the disc since this can affect you new pads - use methylated spirits.

  • Fit the disc to the flange, and tighten the two screws to 7 Nm. Ensure the disc runs true. Rotate the disc and if you can see a wobble on the outer rim of the disc, there is either something wrong with the disc or the way it has been fitted.

  • Fit the carrier to the hub, fit the 2 bolts and tighten to 85 Nm.

    Click to enlarge Click to enlarge Using (ideally) a piston windback tool, screw the piston back into the caliper until it is fully retracted. This may cause the Brake Fluid Reservoir to overflow, so clear up any spillage immediately.

    Click to enlarge Fit new brake pads.

  • Fit the caliper to the carrier, fit the two guide pin bolts and tighten to 45 Nm.

    Click to enlarge Grease the inside face of the wheel where it mates with outer face of the disc. This will make it so much easier to remove the wheel next time. Fit the road wheel and tighten the wheel nuts, remembering that you will have to torque them up fully once you have dropped the car back onto the ground.

  • Repeat for opposite wheel.

  • Remove axle stands and lower vehicle.

  • Torque wheel nuts to correct torque of 70 Nm.

  • Check the level of brake fluid and if necessary top up to the 'MAX' level mark.

  • Now operate the brake pedal several time in order to adjust the brake pads and the handbrake.

  • Now remove the stands and lower the car.