Persistent brake judder

Shoshannah · 18 June 2017 at 1:56AM

I run a 1992 Ford Sierra 1.8 CVH with front discs and rear drums. This model has 240mm discs as standard, but I've run mine with 260mm discs for the past 7-8 years. No other modifications except TCA polybushes.

For the last twelve months, I've had issues with recurrent brake judder. Since Christmas 2016 both calipers have been replaced, a worn wheelbearing was replaced and it's been through three sets of discs and pads.

Within 1000 miles of changing the discs and pads, the judder returns every time. It's worst under hard braking at higher speeds, and is barely detectable below 30mph. The whole dashboard rattles. The judder is transmitted through the steering wheel, but not that noticeably through the pedal.

I've performed the Zeckhausen racing bedding-in procedure twice now, which improves the situation temporarily - presumably because it burns off the uneven deposit accumulation - but this problem isn't going away and obviously something else isn't right around the front end.

I never sit in traffic with my foot on the brake pedal - I'm an avid handbrake user!

My garage, who are generally excellent, seem stumped and I don't want to take it in anywhere if all they're going to do is replace the discs and pads again without looking further into it. What next? A different garage? Back to my usual place? What else could be causing this that they need to look at? Any bushes or hub issues to investigate?

I generally get on well with my garages, and I realise they're very busy, but I'm female and sometimes I do feel like they are less likely to engage in a conversation with me compared to my husband... I do try to open a dialogue when I take the car in, but they always just want to get the car in ASAP with a hurried 'don't worry, we'll have a look at it' and I can't get much of a word in edgeways!

I do a lot of mileage and not only is this problem very irritating but I'm concerned there is something not right with the car that may potentially be hazardous and/or damaging.

Thanks for any insight.

mrmot · 18 June 2017 at 7:12AM

I've had this on mine, luckily at work we have a brake disc skimming machine, as it goes through a calibration process during set up it adjusts to compensate for any hub inaccuracies, the results so far have been judderless braking.

Strider590 · 18 June 2017 at 9:54AM

Some cars are very sensitive to the quality of the pads/discs fitted.
Running larger discs is pointless if the callipers are standard AND with only a part of the disc surface being used, will create hotspots on the disc, I won't say this causes warping, but it will causes uneven build up of deposits from the brake pads.

If your running larger disc with some sort of modified calliper mount/extension, then that is almost certainly your problem.

Putting pads/discs/callipers aside for a minute........

If driven hard, you need to look at the brake fluid, standard stuff isn't going to cut it, you want to make sure the flexi hoses are not bulging (this would apply uneven braking force), consider replacing with braided hoses.
The master cylinder itself is responsible for ensuring even braking force to each wheel, if this is worn you may get uneven braking, which would gradually get worse, but this would fail the MOT roller test.

There are MANY factors to consider and I feel your pain, most garages will just keep replacing the discs/pads.

Poor quality wheels/tyres can be an issue too, if the braking forces aren't being transferred through the wheels strongest point, then the wheel could flex, cause uneven braking and then this escalates.
If the wheels have spacers fitted for aesthetic reasons, these may be warped.

Old cars like this are rarely in standard format, any combination of bad modifications can cause major issues.

Shoshannah · 18 June 2017 at 10:03AM

Sorry, I should have said in my first post that the calipers aren't standard either - or at least they weren't when I initially upgraded. I'm *assuming* the garage have stuck to that when replacing them, but maybe I'm assuming wrong.

I'm just going to have to bite the bullet and try and get them to talk to me properly when I next take it in. It's hard, I know they're very busy people.

Thank you both for the info - I'll ask about the hoses, master cylinder etc. I was under the impression that skimming the discs isn't recommended if there is an underlying issue causing the uneven braking in the first place - is that not the case?

I don't drive hard - quite the opposite, lol.

Thanks again!

Gloomendoom · 18 June 2017 at 10:39AM

Are the poly bushes worn out? Is there any slop in the suspension joints at all?

wgl2014 · 18 June 2017 at 10:53AM

Shoshannah wrote: »

I don't drive hard - quite the opposite, lol.

Thanks again!

That could be part of the problem if the pads become glazed, could be worth doing a few controlled stops from increasing speeds to get a clean braking surface.

Otherwise could also be worth taking the discs off and thoroughly cleaning any rust from the hub facing, any small deposits here can cause the disc not to sit flat and manifest in brake judder.

JP1978 · 18 June 2017 at 10:53AM

If the calipers have been replaced, how would the garage know to replace them with the upgraded size? Wouldnt they have just ordered the ones that would be tagged to the car from their electronic ordering system?

Im not a mechanic but depending on the timeline, is it possible that there was a genuine issue with the discs warping and in a an attempt to fix it the calipers were changed to the factory supplied size, thus now been too small for the larger discs?

Has the same happened with the discs? Were the upgraded size ordered?

The garage unless told otherwise, wont measure the discs or get a part number from them, they will just order what the computer tells them based on VIN

AdrianC · 18 June 2017 at 11:02AM

You simply won't be able to use the larger discs with calipers or pads intended for the smaller ones. They wouldn't fit. You've got 10mm more radius of disc, and there's not that much clearance between disc and caliper.

BUT... if the larger calipers/pads were used with the smaller discs, it's entirely possible that you could have problems, because the pads would be hanging over the edge of the discs.

Shoshannah · 18 June 2017 at 11:05AM

wgl2014 wrote: »

That could be part of the problem if the pads become glazed, could be worth doing a few controlled stops from increasing speeds to get a clean braking surface.

Otherwise could also be worth taking the discs off and thoroughly cleaning any rust from the hub facing, any small deposits here can cause the disc not to sit flat and manifest in brake judder.

I've done that twice now - the braking thing - it improves the problem temporarily (a week or so).

Shoshannah · 18 June 2017 at 11:09AM

JP1978 wrote: »

If the calipers have been replaced, how would the garage know to replace them with the upgraded size?

I tell them.

Whether they listen/remember or not is a different matter! I used one garage some years ago who said: "it's got different discs to standard you know, we had to order twice!" when I went to collect the car.

I said: "I know it has, I told you when I dropped it off".

In answer to your question, I don't know if they've swapped sizes around again. If they have, they haven't told me.

This is a communication issue I think!

System · 18 June 2017 at 11:41AM

On my Ford Capri that "warped disc brake judder" was actually caused by worn bushes in the bottom track control arm. It felt exactly the same as a warped brake disc and was a common fault on old Capris and Escorts often mis-diagnosed as being the discs. Given how cheap they are, I would suggest replacing them especially if they've not been done for a long time. I know you've polybushed them but those bushes don't last forever.

Persistent brake judder

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