Vibration under braking.....sometimes

[DWH]

Hi.
I had a hard noise when braking from high speeds and when then car was MOTed, there was imbalance between the front brakes.
I decided to replace the front discs and pads and did this last week together with the slider pins which were worn on the nearside caliper. I used Mintex discs and pads. All seemed well whilst driving locally where you don't get the chance to go over 60mph and the roads are reasonably smooth, at least in areas where you need to brake.
I've just had a run to York and back up the A1 covering just over 400miles and when braking at motorway speeds sometimes the brakes were silent and smooth and other times very juddery making the whole car vibrate. It seems that on smooth road surfaces all is fine but on bumpy surfaces where the car is already a bit "unsettled" any touch of the brake pedal results in a very nasty and concerning vibration.
Braking on any road surface at slower speeds (below 45 - 50 mph) is smooth.
Any ideas ?
Cheers
David
2003 1.8T Cabriolet

 

[pauldazzle]

Sticking caliper would be my guess.

 

[vr6gordy]

this happened to me and it turned out to be the pad of the break pad had come away from its backing

 

[desertstorm]

The times when they were juddery was it after you had applied the brakes 2 or 3 times so they had time to heat up ?.
Sounds like pad pick up to me had the same issues with my car but really only when braking hard from high speed . This is pad pick up and could be due to the pads not being run in properly or as above if a caliper is sticking the pad is always rubbing the disc so gets hot. When you have taken the car for a bit of a normal drive, when you stop the car feel the centre of the wheels and see if they are the same on the front.
New Pads and discs always run hotter till they have bedded in.
The fronts will always be hotter than the rears but should be the same both sides.
I cured my problems by switching from Mintex to some Redstuff pads.

 

[john777w]

I agree check brake temps, be careful they get hotter than you expect!

 

[vr6gordy]

It's all well and good having a guess at the problem .. Best way is to take wheel off and have a good look

 

[ruffrida]

Could be a sticking pad in the caliper. Seen this enough times.

 

[vr6gordy]

Take calipers off and clean the sliders and then grease the sliders up .They are easy to undo only held on by 2 7mm Allen key bolts

 

[Jimmy TDI]

He says he replaced the sliders for new ones.

If it's only happening on rough roads it could be that you have worn bushes in your control arms/ARB, and the braking is exagerating the vibrations.
I had a similar issue on my Mk4 and it was the rear lower arm bush that had failed causing judder under braking.

 

[Mike_B]

x 2 on control arms - new rear lower arms has produced a considerably better ride / braking, despite them seeming to be ok both at MoT and a subsequent investigatory inspection.

 

[Greeny233]

I had a similar problem with mine, i would only get judder when braking hard from higher speeds but they were fine everywhere else, the discs and pads were new. I haven't had a problem since upgrading to the S4 345mm conversion. Perhaps its a very small imperfection in the disc which only shows when braking harder for longer.

 

[Mike_B]

One additional thought - might be worth getting your garage to put the car on the brake tester again - I replaced the front discs and it turned out one was faulty, resulting in the higher-speed vibration you've described. So far, touch wood, the replacements are fine.

 

[DWH]

Thanks for everyone's responses.
I'll take the wheels off and check the pads are seated properly, then see if anything looks amiss.
Breaks feel totally fine again today on normal A roads up to 60mph.
Thanks again

 

[john777w]

When you drive at speed can you feel any vibration through the car?

 

[DWH]

None whatsoever, steady as a rock and the brakes are feel perfect (good feel and even braking with no pulling to either side) all the time below 60mph but above that at motorway speeds, it's a fifty fifty gamble whether its smooth or whether the car feels as if its falling apart.

 

[john777w]

Just asked as I had a rear wheel balance problem, that amplified a brake judder on the rear!

 

[DWH]

The problem has gone. I haven't done anything at all except take the wheels off to check everything was fitted correctly and tight, which it was. After driving the car for 2 weeks including some very wet weather, the judder has never reappeared. I can only think there was something on either the discs or the pads that has now been rubbed off.
Thanks for everyone's responses.
Cheers !