MINI workshop - Brake disc change
An unpleasant metal on metal grinding noise as the brake pedal was pressed announced the fact that the brake pads no longer had any friction material, which was a bit of a surprise as Kato - our 2002 MINI Cooper S was only half way between its first and second service. Even more surprising was the fact that it was the rear brakes not the front as expected.
Just like punctures only happen on dark wet and windy nights, the pads reached the end of their life at the start of a long journey on a Sunday so there was no chance of replacing the pads and it would be some 400 miles before we would be back home. Luckily most of the braking is done by the front wheels - which is why it was a surprise for the rears to wear out before the fronts - and it was therefore possible to continue safely if rather noisily although with the certain knowledge that the disks would have to be replaced.
Later MINIs should have a low pad level sensor to signal an impending change but the 2002 model does not.
With the front wheels chocked and the wheel nuts loosened (17mm socket), it should have been a simple matter to swap the disks and insert a new set of pads, however Kato had other ideas. The rears wheels did not want to part from the hubs. The rear of the car was supported on axle stands such that the wheels were just clear of the ground and a block of wood found that reached the rims. Then by hitting the block with a mallet and rotating the wheel from time to time, the wheel was finally prised from the hub but it took a lot of effort. It is just as well that the car is fitted with run-flats as I would not liked to have tried to change a puncture at the side of the road.
The problem was that the center of the wheel was stuck on the raised centre of the hub, the aluminium/cast iron mix not being the best combination. Coppaslip was applied before the rims were replaced.
With the wheel out of the way, the next job was to remove the caliper. Start by removing the wire clip that holds the pads and sliding the pads (or what is left of them out)
The caliper has a single piston, so the body of the caliper slides on a pair of pins as it grips the disk. Prise out the two platic plugs that protect the ends of the pins.
You will the be able to undo the pins using a 7mm Allen key which will separate the caliper body from the bracket that holds it to the hub. Tie the caliper up to the suspension to avoid straining the hose.
This is the bracket that holds the caliper to the hub, and it must be removed before the disk can be taken off.
There are 4 bolts here, only remove the two that hold the bracket (13mm socket)
The disk can now be released by removing the setscrew using a Torx T50 drive.
As they say in all good manuals, assembly is the reverse of dismantling, the piston will need to be pushed into the caliper to make room for the new pads, so make sure the brake fluid does not overflow the resevoir.
Before driving, press the brake pedal until the slack is taken up.