Ed Evans of LRO Magazine continues his article on how to change the discs on your Defender……..
Rear disc brakes have been fitted to all Defenders (except military models) since 1994.
1. The rear brakes have a smaller single-piston caliper with split pad-retaining pins, and plate springs. Flatten the pin ends and withdraw them.
2. Otherwise, the job is the same as for the fronts, except the caliper lifts straight off with no brake pipe plate to be released.
The Britpart Performance Discs fitted here are uprated by being grooved and drilled (110 and 130 Defenders are built with ventilated front discs).
The grooves in the face of the disc help dispel water, grit and dust, aid cooling and increase braking efficiency. Holes drilled around the disc also assist cooling and provide another escape route for dirt.
The grooves are angled – as you can see on the photograph below – to benefit from the disc rotation in ejecting debris, so the discs are handed (as marked on the packaging).
We fitted standard pads to the new discs. Alternatively, EBC produces a range of uprated brake pads. Included among them are the well-known EBC Green Stuff pads, which are claimed to be longer-lasting, quiet and quick to bed in. These are suitable for general road and off-road use.
WHILE THE DISCS ARE OFF…..
Check that hub bearings are smooth and free, and look for signs of leakage. If needed, now is a good time to renew the hubs’ bearings and oil seals. However, this will normally involve measuring the hub end float with the new bearings and selecting a new spacer to suit.
Grooving is easy to see: it renders the disc inefficient, especially when new pads are fitted. Watch for the first signs of rust pitting, which will rapidly deepen, destroying the pad faces.
Front discs can warp, causing a shimmy at the steering wheel or pedal pulses when slowing. This is often caused by holding the brakes on at a junction after heavy braking, when slight misalignment of pads or caliper pistons can distort the hot disc permanently. To confirm, a dial test indicator (see Workshop Tips below) needs to be used to measure run-out.
Damaged discs can be machined to create a new face on each side, providing they
still have a minimum remaining thickness stamped on the edge of the disc. The relatively low cost of new discs means renewal is the best option, especially as a thinner disc is more likely to warp. Discs can wear too thin if they’ve had heavy use, or if high-friction performance pads are fitted.
Brake squeal can be caused by corrosion or dust building up on the pad seats in the caliper, or on the caliper pistons’ working edges. The caliper pistons may also be sticking, or the pads’ seats could be worn on a high-mileage Defender. Genuine pads are chamfered slightly on their leading and trailing edges, and it may help to do this on aftermarket pads that aren’t chamfered.
Use a 12-point socket to avoid rounding the heads of the caliper bolts. If the bolts are corroded, try tapping an undersize 12mm socket on to get a vice-like grip. Before releasing, wire-brush and wash off the top swivel bolts and brake plate to prevent dirt falling through the bolt holes into the swivel. The hub nut will be damaged during removal when the peened section breaks away, so always fit a new nut. The part number is RFD100000. If nut removal damages the thread on the stub shaft, clean it up carefully with a fine triangular file – or, better still, a thread file. If you have a dial test indicator, check the run-out of the new disc when the hub is mounted on the axle. If run-out exceeds
0.15mm, unbolt the disc and check the mating faces are flat. Remove any dirt or burrs and refit. If the faces are good, try rotating the disc 90º and rebolting. When refitting the drive flange, temporarily screw a flange bolt in the shaft centre to hold the shaft outward while tapping the drive flange home. Ensure caliper pistons are pushed back before refitting the caliper. Clean the edges of pistons, and the caliper’s upper and lower pad seats.
The above content originally appeared in LRO magazine and is reproduced here with their kind permission. Any advice or opinions are those of LRO magazine and its writers.