Eclass brake tramping

[Gangley]

I have changed the discs and pads 3 years ago with original parts on my 1997 merc due to tramping. It is starting again despite being light on the brakes. The vibration does not seem to affect/transmit to the steering feel, or the maximum braking effort. It is definitely associated with road/tyre speed.
I have just taken both front brakes apart and checked the discs for sign of uneven wear but they seem fine- as new. The pads are not even half worn and parallel surfaces and everything is fee and servicable. Has anyone any ideas?

I am told the car only applies the front brakes under light braking and I can feel the tramping then. Would this isolate the problem to the front discs being warped AGAIN? What a useless car for a quality model.

 

[wireman]

I have found that the rear disks on 124s are much more likely to cause this sort of problem, especialy on cars which dont get their brakes used regularly with some deliberation.

The rears are operated proprtionaly with the fronts but at a reduced pressure (~30%ish)which is often insufficient to wear off any rust that forms on the disk edges when never called upon to do any hard work.

Take out the rear pads and inspect the back side of the rear disks, expect to find a poor suface where the rusty periphery of the disk is speading inwards across the working surface of the disks. In my experience on the 124 this is a common cause of both a slighly poor pedal feel and roughness and lumpiness of the ride during braking.

The cure is to replace the back disks, its a repeat of the front job but with a drum brake in the hub to make it a bit more interesting, replace that as well whilst its in bits.

An occasional full stregnth stop from high speed can help obviate this trouble, or removal of the pads and scrubbing of the disk with abrasive paper at normal service intervals.