Any thoughts please people.......

I had my rear discs and pads replaced a couple of weeks ago and have just noticed a slight juddering when I apply the brake - minor when braking from 30-40, slightly worse under harder braking from 70-80 (ish...!!)

Obviously first thoughts are dodgy front discs/pads......

Took it back yesterday and they are now telling me that the front discs are warped (pads are fine)

Just seems odd to me it's only happened since the back brakes were done, or is it coincidence?!

I have also been told that it may be caused by a 'film' on the pads so they might need roughing up a bit.

Last note - the juddering definately gets worse the warmer the car/brakes are.......

Cheers gents

Are they genuine discs or 'cheaper' alternatives?

Definately genuine.......

the film your refering to should have been cleaned off with some solvent before they ran it so i doubt its that.

does it only do it under breaking or is there a wobble all the time?

Disc runout? even though gen, can still happen!

Only happens under breaking....

How do you mean disc runout???

Disc run out is contact between disc and pad when your off the brakes, because the pad and disc always sit close together any distortion of the disk over a certain amount [0.10mm] will cause contact between pad and disk when off the brakes.

This can be caused by variation in the disk itself, a warped hub or the hub not being cleaned properly before the disk was fitted to it.

The run out should have been measured before the new discs were fitted.

yep...!

Also consider a sticking brake caliper, especially after you have just had new pads fitted. It is a common thing when pads are fitted as the piston is pushed out further than normal and all it needs is a bit of crap on it to cause it to stick. When you brake it sticks and this confuses the ABS which makes it feel worse. This happen to mine and after cleaning it was fine. Cheaper than replacing discs when they are not needed.

Steve.

Cheers Steve,

What do you think then, clean off the discs and the pads?? Don't really know enough about the brakes to start taking them apart if I can help it!!

......sorry for being a bit slow....... it's been a loooong week......!!

If you don't know what is what with brake then leave well alone, get someelse to do it, going out on a limb but if the discs are genuine they do they not carry a warranty from the stealer who supplied??

Who fitted them, if it's seized due to crap on piston they did a piss pour job, piston should be cleaned before being pushed back, just good practice, IMO. If they didn't do that i doubt they checked the run out.

Sporty1 wrote: Who fitted them, if it's seized due to crap on piston they did a piss pour job, piston should be cleaned before being pushed back, just good practice, IMO. If they didn't do that i doubt they checked the run out.

If the dust seal is intact then there shouldn't be any crap on the piston in the first place and if the dust seal wasn't intact then it should of been sorted there and then .

If they are saying the front discs are warped then that is more than likely the case , it sounds it from the symptoms you describe.

Does the pedal seem to push your foot back under lighter braking ?

this is usually a sign of warped discs , as when they run out of true the disc pushes the caliper piston back therefore raising the pedal slightly. (as stated under light braking so you can feel it )

If i have read the post correctly the garage replaced the rears and its the front that they are saying are warped yes ?

cheers

Andy

when the judder is evident can you feel the vibration or wobble through the steering ? if you can its definatly the fronts, if you cant it still could be fronts but not bad enough to travel through the steering, have a look at the rear discs and see if any part of the disc is discoloured part way round etc, ive also know judders come from the fitter not cleaning the hub flange where the disc sits onto, thus cousing the disc not to seat square etc. fitters fault that one....

just a couple more things to try for you there

Its not the pads and the discs that would want cleaning if the caliper is sticking it would be the piston but I agree with sporty don't mess with them if your not sure what is what. If you had not experienced this judder prior to the new pads being fitted then unless you had been on a track day, done a lot of really heavy braking or done a lot of miles with your foot on the brake then I do not think your discs are likely to have warped in such a short time. OEM discs on an M3 are made to cope with some serious use so normal driving for a couple of weeks should not warp them. If however they had been binding creating a lot of continuous heat this could warp them but the effect on performance would have been very noticable and you would have smelt the pads burning.

If you know another good local garage get a second opinion.

andyclient wrote: If i have read the post correctly the garage replaced the rears and its the front that they are saying are warped yes ? cheers Andy

Just re-read the original post, and your right, it says rears, I must have missed that this morning, so I'll just get my coat..................

hornydevil wrote: Just seems odd to me it's only happened since the back brakes were done, or is it coincidence?!

It may not be coincidence , If the person who then road tested the car employed some really aggressive bedding in techniques for the rears then this could indeed warp your front discs

(fronts do most of the braking so would get hotter than the rears being bedded in , if the pedal was then aggressively pumped  whilst the fronts were hot it could warp them )

Garages do tend to bed brakes in fairly hard as they don't want the customer roaring down the road and not stopping at the first junction Cue injury lawyers direct  !

but proving that or getting them to admit liability are two different things i'm afraid

cheers

Andy

Many thanks for all your comments......

Right then..... just to clarify.......

Steven/Andy - yes, as you've noticed, it was the BACK discs and pads replaced and i've now been told that the FRONT ones are warped.. haven't noticed the pedal pushing back as you asked Andy

Sporty - discs were fitted by my local indy, so I assume there will still be some sort of warranty

Neo - yes, I can slightly feel it through the steering SOMETIMES, so I've got to assume it is the front I suppose....

However, saying that I didn't feel it last night under heavy or light braking

Something else I've just noticed though..... the NS new rear disc is marked/discoloured already closest to the hub all the way around the disc and about a half inch wide - the OS disc is unmarked. Only done about 150 miles since they were replaced - what do you reckon to that?!

Think I'm gonna take it to someone else to have a look..........!!

Thanks again for all your feedback