Brake juddering

[marv]

Hi all,

The last few weeks I've noticed slight juddering under heavy braking.

I assume this will be down to worn front brakes? I've had the car for nearly 18 months/10000 miles and haven't changed them in that time, so I have no idea how old they are.

Given the judders, would I be right to assume it's more likely a problem with the discs than the pads, or could it be either?

Will it be a case of replacing the discs AND pads either way?

Cheers

[nihc]

Hi,

It depends on whqt the judder is like.
A lot of people mistake warped disks with pad deposition on the disk.
I've had this on the S4 and it felt like I had badly warped disks for a week.

When the disks get very hot the pad composition can embed in the surface of the brake disk in an uneven way and you end up with areas of the disk that have a lot more friction ( grip) than others and it feels like your disks are badly warped.
That could be your problem - it will go away in a few days with a bit of heavy braking.
How worn are your pads - what's left on them?
Did this just suddenly happen?

Regards, Chris.

[marv]

Thanks for the advice.

I'm not sure what's left on the pads at the moment, I'll have a look tonight if I can find a torch!

It does seem worse at the end of a long-ish drive, so heat could be a factor.

It did seem to come on without warning, and apart from the difference between the start of a trip & the end, it hasn't got much worse over the last few weeks.

[cfoster]

I get something very similar on mine when the brakes are warm, I put it down to knackered/warped discs as they have a big lip on them already!

[marv]

Do these cars have low brake warning sensors?

[BlingBling]

The pads have sensors inside them. The discs not.

[xyber]

Get a vernier gauge on the discs and see how thick they are. Mine juddered when I got the car because it needed new discs and pads

Check you hav'nt lost a balancing weight and that the wheel studs are tight as well

[wolf02]

Had the same problem on mine, I replaced the disc (needed doing anyway "probably" as I tell myself).
What it turned out to be was the new pads i fitted had left some residue on the surface of the disc (in multiple places).
Only spotted it when I replaced the pads, on the inside of the pad on both sides there were black lines of brake residue, causing the pad to skip when it hit these points.
This made it feel like the disc was warped. Im sure if i had done a bit of heavy braking it would have worn away and been fine but as I had the replacements in my hand i fitted them anyway.

[marv]

I'm getting this looked at next week by RCMR - a local specialist, very good I'm told - so I've bought a new set of discs & pads which I'll get fitted at the time, irrespective of whether they're the cause of the judder, as I haven't had them changed since I've had the car.

I haven't got a vernier gauge, but from what I've read of the disc specs, the start thickness is 30mm and the minimum thickness is 28mm, and I'm pretty sure the lip on the visible side of my disc is 1-2mm. So I'm assuming the lip on the other side of the disc is a similar size, and therefore the discs would be at or beyond min. thickness.