Handbrake Adjustment
My 730i failed NZ's Warrant of Fitness test because the left rear parking brake stopped 60% better than the right. FYI, the parking brakes on all rear disk-brake bimmers consists of a tiny cable-operated drum brake inside each rear rotor. They are too small to be considered an "emergency brake," only just big enough to hold the car on a hill. The brakes have conventional manual "star" shoe adjusters at each wheel in addition to a cable adjustment at the lever for each side.
Here's what I did to check and adjust the parking brake system. Sorry, no pics, I was in a hurry.
a) Place the rear of the car on jackstands and pull the rear wheels. Or do one at a time if you wish.
b) With a 15mm socket, remove the caliper and place aside with the hydraulic hose still connected. Unplug the brake sensor on the right side.
c) Be sure the handbrake is off. Remove the single screw holding the disk to the axle hub. Pull the disks off. If it doesn't come off, check step (c) again :)
d) Check the condition of the shoes and drum. Wire brush off rust as required around the hub seating area. If the shoes need to be roughed-up, use a coarse file or sandpaper. Check the brake adjuster "star" screw and get familiar with (and write down) the direction required to spread the shoes apart.
e) Replace the disk and single screw. Tighten gently.
f) Pull the plastic bezel around the handbrake and check that the cables are slightly loose with the brake off. Adjust as needed.
g) Be sure the shifter is not in park and the handbrake is fully down. With a flat-blade screwdriver, turn the adjuster star (accessible via one of the holes in the brake disk hub) until it's tight and the disk doesn't turn. Then back off 3-4 clicks. The disk should spin free.
h) Repeat on the other side and replace the wheels. Leave the back raised.
i) Lift the handbrake normally and check that the torque required to turn each of the 10mm cable adjusting nuts is about equal. Adjust to suit, tighten or loosen keeping in mind you want 3 or 4 clicks to fully operate the handbrake. Road test and adjust the 10mm nuts further as required.
On the re-test, now the left brake was 15% higher but it passed. Oddly, or perhaps for redundancy, the two sides do not self-balance like many other cars do. Another BMW curiosity.