Vibrating rear brake

We are all used to tales of noisy brakes but my rear actually vibrates so you can feel it all the way to the seat. It is a Guide RE on a Vitus E Sentier. I was told reducing disc size would help so I went from 200mm to 180 both Centreline with no effect. I have changed pads, wheel bearings and have run out of ideas. Any suggestions?

Stupid suggestion probably, but have you checked the brake is actually bolted on tight? Ditto is rear wheel tight?

I had this with SRAM Level brakes on my Trek Superfly.

Nothing cured it until I taped a lead wheel balancing weight to the seatstay which calmed it down somewhat, but replacing the brakes with Deore ultimately solved it.

sounds lke something not aligned properly. Have the brake moutns been faced correctly, is the caliper properly fitted?

I had this issue with some old SRAM brakes – it started with a rotor with a ‘sticky’ spot, and became a whole of frame vibration. What the cause was I have no idea as I sold the brakes and rotors and went Shimano new everything – and that solved the issue….

Just came to to add bout facing mounts and ensuring spacers are allowing correct alignment

As far as I can see everything is aligned properly and tightened. I might just have to give up and buy some Shimanos. Pity because the REs actually stop very well, it’s just the teeth rattling vibrations