Opinions please...

[DavidR]

I have fitted a new set of OEM front brake discs and EBC green pads in the last few weeks. After the whistle, screech and burning smell of bedding in everything seems fine until now, under fast braking 90-100mph plus there is judder through the car, similar to that with the old pads / discs. Slow braking from 70-80mph is v. effective, and v. smooth.

I would hope that the OEM discs have not deformed already (and the surface is clean and not obviously scarred) but am concerned as I have EBC grooved ones on order and am worried that the problem may lie in the hub or somewhere else.

Any thoughts on causes and or things to check?

Cheers

David

[Andiroo]

How many miles on the new disc & pads David? Take it fluid was changed also? Any maintenance on caliper pistons?

Just trying to get a feel as to what could be wrong [img]images/graemlins/wink.gif[/img]

Andiroo

[DavidR]

About 700, mixed MWay and heavy stuff.

Fluid changed at last service (approx 1000miles b4 brakes)

Caliper as was, 40k total miles, not obviously siezed when dismantling to swap disk and pads.

[Andiroo]

Well bedded in then [img]images/graemlins/wink.gif[/img]

Apart from the obvious warped disc (shouldn't be so soon), I would try deglazing the pad surface. I have found with abrasive pads that the heat generated is greater than OEM and tends to reflect back into the pad surface and create a glaze effect. Solution is to take them out, fairly easy to do, and take a dremel or hard sander, and take off all the sharp edges and a the glazing off the surface. Put them back on, bed gently in for about 10 miles - then give her some stick [img]images/graemlins/tongue.gif[/img]

Either all will be OK, or your disc(s) could be warped [img]images/graemlins/frown.gif[/img]

Cant see it being anything to do with the caliper pistons as you would have the same vibration at 70mph.

Good luck mate [img]images/graemlins/wink.gif[/img]

Andiroo

[DavidR]

Would glazing of the pad surface affect the retardation? I ask this as it still stops with tremendous effect even from high speeds, and if anything braking force has increased through the bedding in period.

Thanks for your replies...

[Andiroo]

It's all I can think of re the vibration you are getting at very high speed (apart form the bad news of warped discs [img]images/graemlins/frown.gif[/img]) - I had a similar problem with Pagid Yellows and it worked for me [img]images/graemlins/laugh.gif[/img]

Andiroo

[DavidR]

Cheers, i'll give it a try although i think it is a caliper off job as there is not enough room to remove pads with caliper in situ even with pistons all the way in [img]images/graemlins/smile.gif[/img]

[DavidT]

Any progress on this David ?

Are you on original discs ? Audi told me mine needed replacement when I had it serviced at 40k miles, but when I looked at them, they were fine.

[DavidR]

Pads deglazed with no difference. New discs were fitted at the time of pad change so I now have 2 options. Firstly I'll take the disc off and get a wire brush drill attachment and clean the hub (again) in case there is dirt there causing run out. If that fails, I'll take the discs (which have done only 900miles) to a local machinist and get them checked with a dial guage. One thought is that one or both of the discs have a manufacturing defect?? [img]images/graemlins/24430-audibash.gif[/img]

I am having difficulty getting anyone to check the condition of the hub (as I guess that could be a source of runout also). Waiting for decent discs to be made (i.e. EBC ones)....

[SJS]

Just a thought, but have you trying pulling the fuse on the ABS system.

I had a similar problem a while ago when the ABS kept kicking in at higher speed braking.

On my FWD A4 i had 2 slightly smaller tyres on the front for a track day and these were causing the problem. Obviously when i braked the computer was seeing the front of the car supposedly going quicker than the back and crapped itself.

Pull the fuse and try it. Quick way to rule a few things out if nothing else.

[DavidR]

Thanks, but its definately not the ABS. ABS judder is confined in my car to the pedal and the pressure in the pedal changes as ABS / EBD works. This is something more mechanical as it comes through the steering wheel too.

[Simon]

sounds to me most like warped discs.

distance is not a factor more of how they have been used, you mentioned whistle screech and burning while bedding in? I thought the general rule was gentle braking for the first 2-300 miles or so while gradually bringing the dics/pads up to temp. and then letting them cool to condition them.

If you are getting the pads hot enough to be burning while bedding in I'd say you are giving them to much stick to early.

Simon

[Nige_RS4]

I fitted EBC greenstuff some 1k miles ago on new'ish (5k miles) OEM discs. Brakes have been transformed - no fade on the road (yet), better fell, less brake dust BUT I do get a grinding type of noise and a very, very small amount of vibration though the pedal and wondered if this is what you are experiencing. Spoke to someone in the know and this is apparently quite common with EBC and other uprated pads ??

Nige.

[wazza]

I went to EBC greenstuff last october. Much better stopping power [img]images/graemlins/laugh.gif[/img]
I now get the same vibration, but really quite bad once they are very hot. Once I eventually get the Castle Combe video downloaded you will hear what I mean [img]images/graemlins/shocked.gif[/img]

[DavidR]

Yeah, the vibration is there and is just that the pads keep biting whereas the old ones would fade - and this only happens when the brakes are fairly hot.

My latest theory re this problem is that the OEM discs are poor quality , and as they heat up, the bell deforms causing vibrations and the warped disc feel.

COME ON EBC, MAKE THOSE DISCS FOR ME SOON [img]images/graemlins/thumbs.gif[/img]