BMW E39 steering wheel shakes when braking
E39 steering wheel shakes when braking - what usually causes it?
The cause is often play in the front axle: worn thrust arm and lower control arm bushings or joints. A sticking brake caliper and a warped disc or hub can also cause shaking, but on the E39 they are less common.
How do I check the thrust arm bushings and joints?
Lift the wheel off the ground. One person turns the tyre, another holds the joint and feels for play. When replacing, the thrust arm bushings must be fitted the right way round, and tightening and alignment are done with the car standing on its wheels.
What do I do about the brake caliper if the discs and pads are new but the shaking remains?
Check that the caliper pistons are not rusted or stuck, and that the slide pins and pads move freely. The pistons are carefully cleaned and lubricated with a suitable grease, and the slide bolts and rubber bushings are renewed if needed.
How is disc runout measured?
Runout is measured with a dial gauge on a magnetic stand. Without a dial gauge you can do a simple marker-pen check on the disc. The contact surfaces of the disc and hub are cleaned shiny when fitting a new disc.