Brake pedal goes up and down when pressed/wobble

[Johnmed]

Hi all.

I replaced my discs and pads a few thousand miles back. The discs were past their best and I was experiencing some wobble/pedal moving up and down and some groaning like Whales mating when braking.

Took my time changing discs and pads, cleaned and copper slipped everything. Drove really gently for a good few hundred miles. All seemed ok. Since then the groan has returned at slow speeds and now the wobble/pulsating/pedal moving up and down under my foot noticeable at M’way speeds and grabby brakes at low speeds.

I didn’t replace slider bolts or shims as they all seemed ok. The brakes are not binding, and the car doesn’t pull to either side.

Does anyone have any theories as to what I’ve done wrong or how to rectify?

Thanks in advance.

[Mechcanico Lee]

What make of discs and pads did you use ?
Did you get any rust build up off your the hub face ?
Did you check hub run out with a dial test indicator ?

Very often with new discs that re warp it’s because the hub face is not flat and square , you fit the new parts and all seems ok until a few heat cycles and the discs starts to take the shape of the warped hub .

Another one .....do you ever coming flying off a motorway and do mega braking to the end of the slip road ,then sit there at the junction or lights or whatever with your foot still on the brake pedal .....this can put massive localised heat into the area of disc where the pads are clamping it ....this can set off a warp issue .

Another one .....DTV.... disc thickness variation , on bedding in new discs and pads they normally have a bedding in surface , in some cases if not done properly the cementite in the pads can bond to the disc causing DTV ....it gives same symptoms as warped discs ...pumping of pedal

It’s said that your not supposed to use copper slip between the disc and hub face it should just be clean and grease free , if anything don’t use copper grease where you have metal and aluminium together e.g aluminium wheel , aluminium calipers and so on..... copper between diss similar metals can cause galvanic corrosion , there are non metallic greases for these purposes like Ceratec , copperslip is ok where it’s metal on metal .

[Johnmed]

Hi Lee.

Thanks for that. Discs and pads are Brembo. I wire brushed the hub surface before fitting the discs and used copper slip sparingly on the caliper where it meets the shim and brake pad metal.

Previously I’ve bed pads in slowing from 50-40 mph without stopping etc, but this time I just drove very gingerly for a good few hundred miles.

I’m not heavy on the brakes and don’t use them when stopped, preferring the EPB.

[Mechcanico Lee]

Was the Brembo stuff off Euro car parts ?

[Johnmed]

Originally Posted by Mechcanico Lee

Was the Brembo stuff off Euro car parts ?

Yes mate. Why?

[tc4332]

Waiting for Lee's educated response with bated breath.
Have Europarts dropped another clanger?
Oh dear, hope that it is a quick and easy fix John.
You know where I am if you need some assistance with the loud swear words