Brake vibration

[tapkaJohnD]

This is on my Citroen C5 2014.

There is a marked vibration on ordinary braking, felt through the pedal and the car. LESS noticeable on harsh braking, but still present.
Inspection of the calipers shows correctly installed pads with adequate thickness, and normal discs.

Could this be a fault with the antilock system, pulsing the brake pressure under lower pressures than it would normally?

John

[GreenV8S]

Hard to guess, but the symptoms don't really point to an ABS problem.

I'd suspect that either there's a problem on one of the brake rotors (dirt trapped behind the disk, uneven pad deposits and heating causing uneven wear and 'warped disc' symptoms etc) or a loose/worn suspension bush/joint allowing things to flex where they shouldn't. Heavy braking might take out the play and reduce the symptoms.

[Scrump]

Have you checked both faces of the discs?
Some cars have a tendency for the inner face of the discs to corrode whilst the outer faces appear okay.

[6times7]

Try rebedding the pads, 5 vigorous stops from 70-10mph followed by driving Mrs Daisy for enough miles to let things cool down

I'd be surprised if that sorts it unless you've had a spirited run out and parked hot recently (you did say Citreon C5), but its a lot cheaper first step than getting into ABS faults etc.

[Smint]

Possible caliper piston or slider(s) sticking, did you remove the pads check for free movement of all moving parts clean and lube correctly before refitting, that would be my first job.

[Dave Brand]

6times7 said:

Try rebedding the pads, 5 vigorous stops from 70-10mph followed by driving Mrs Daisy for enough miles to let things cool down

That's what I'd suggest. Worked on my Alfa 147!

[ninjag]

Smint said:

Possible caliper piston or slider(s) sticking, did you remove the pads check for free movement of all moving parts clean and lube correctly before refitting, that would be my first job.

This ^

And also check that the slide pin boots haven't swollen, just in case someone previously used copper grease to lube the slide pins.

[tapkaJohnD]

I tried the "Re-bedding" procedure (simple things first) and it has had a good effect.
Vibration much diminished, although still present.

Thanks, I'll keep the other suggestions in reserve.
John

[neenoy]

That suggests that the disc surfaces are not even - corrosion and or pad deposits. As discs are cheap and I would change them myself, I usually get fed up of rough braking and just replace the discs if they appear to not be completely recoverable.

An interesting phenomenon that I previously thought very plausible; I watched the brake values of our 2016 Tucson deteriorate every year (our dealer does a brake test at each service) until I replaced the discs and pads, when they bounced straight back. The surface of cast iron discs goes harder/less friction with corrosion cycles. With affordable disc, it isn't such a bad idea to change them out every few years even if they aren't totally worn down if performance drops off and they don't brake smoothly any more.