Cleaning my wife's Sport last week, I noticed a hairline crack on the rear brake disc. Rather than wait to book the car in, I decided to undertake the repair on a sunny afternoon.
Assuming that you have access to basic tools and are mechanically competent, the repair process is pretty straightforward. Having said that, I accept no responsibility for works that any of you undertake, nor the consequences, either!
I ordered a set of discs and pads from Lexus Twickenham - no discount, but the parts arrived within a day as promised (pads are a stock item anyway). On hindsight, I would have ordered anti-rattle springs as well as although they usually remain intact, I have known them to be damaged upon removal, and do not come supplied with the pad set. Always replace brake discs in pairs, unless there are exceptionally extenuating circumstances for not doing so. They are quite cheap at around £80.00 each as well - I had expected them to be double. Equally, if you are going to fit discs, do not be tempted to economise and fit the old pads - fit new every time.
Jack and support the car, having first loosened the rear wheel nuts whilst the wheels are resting on the ground. The front wheels should be chocked before jacking, the parking brake released and the transmission left in Neutral, not Park.
Remove the rear wheels, then remove the two bolts that secure the caliper assembly, gently lever this clear and place it out of the way - it will be hanging on by the brake hose and care should be taken to avoid twisting the hose unnecessarily.
Remove the two V-shaped pins that fit into the outer edge of the pads, then the pads themselves, noting their position and also anti-rattle shim positions on each one - the inner pad has a looped piece of metal attached. There should be four anti-rattle shims in all - two on each brake pad.
At this point I transferred the anti-rattle shims to the new pads, cleaning each shim and coating it with a light smear of brake grease (this is usually gold in colour). Take special care to avoid getting any grease onto the friction surface. WD40 may help too, if sprayed on a few minutes in advance.
Loosen the two bolts that are now retaining the caliper bracket and remove this - might take a tap with a hammer and bar - and use 1/4 "drive, as 3/8" is likely to be too fragile.
At this pont the disc should drop off following a tap or two to loosen it - if not, the handbrake drums, which are located to work inside the disc hub, might be sticking, or the disc hub may be slightly grooved internally.
Rotate the disc so that the fitted rubber plug sits at the bottom six o'clock position, and remove it.
Behind this is a hole in the disc, which enables you to slacken off the handbrake freeplay adjuster if necessary. Use a thin flat-bladed screwdriver to rotate the knurled adjuster from top to bottom, which will ease off the brake linings so that the disc can be removed.
Fit the new discs (assuming that the handbrake linings are not found to be badly worn - they get minimal use and should be fine, unless somebody has ben a dumb-***** and driven around with the handbrake on).
Re-adjust the handbrake adjuster, this time moving the knurled wheel from bottom to top until the disc just binds as you try to spin it, then back off a turn or two to ensure that the disc can rotate freely.
Don't forget to refit the rubber plug to the access hole....
Refit the caliper bracket with the two original bolts, then use a sizeable g-clamp to gently compress the brake piston until it is flush with the housing, enabling maximum clearence to enable the new brake pads to be fitted. Do this slowly, or you will have brake fluid spurting out of the resevoir in the engine compartment. Alternatively, I have used a large flat-bladed screwdriver to lever the caliper open whilst the old pads are fitted (better clearence).
Re-attached the caliper using the two original bolts (I usually smear a little grease on the thread to prevent any possible seizure in the future).
Refit the roadwheel, tighten the bolts and just lower the wheel enough to torque them properly before fitting the cenre cap.
Repeat the process for the other roadwheel, then check and pump the brake pedal and handbrake before attempting to drive.
Assuming that you are happy that everything feels normal, then gently roadtest, remembering that new brake components require time to bed in before they reach maximum efficiency, and also to promote longer life expectancy.
Now sit back and make a nice cup of tea - you've earnt it.
If everything went to plan, you will have completed everything in well under two hours - and do remember that effective planning is always the key to a sucessful operation.