BMW E34 brake judder and sticking caliper
What causes the vibration when braking in the E34?
The most common causes are a warped front brake disc and a sticking brake piston. Also the radius arm bushings or ball joints can cause vibration, and tyres or wheels vibrate at certain speeds. The cause cannot be known without an inspection: replacing the disc fixes the fault only sometimes.
How does a seized brake piston show up and how can it be fixed?
A seized piston can shake the car violently and heat the disc and caliper. The caliper is taken apart, and the seals and brake fluid can be replaced. Brakes are a safety matter, so if you are not sure, have a workshop do the job.
What causes rattling and play when braking?
The cause can be worn radius arm bushings, the control arm ("dog bone") or the upper control arm bushings. Loose bolts on the tie rod tube can also rattle, and tightening them removes the play. A worn suspension can wear the tyres on the inner edge and shake under hard braking.