Brake judder

[idlerider]

Front judder on braking started a couple of weeks ago - slight but noticeable through the pedal...
95 Aero estate - 2003 - 90k. Any thoughts on most likely cause, anyone? Discs? - bushes?
(BTW: don't know what a pair of discs for this would be - but if you think Saab spares are expensive, front disks for my Beemer 635 were £412 each! - and that was 10 years ago.)

[sgould]

Likely to be uneven deposits of brake pad material on the disc. Have you driven hard and then sat at the lights with your foot on the pedal?  Pressing the pad against a hot disc?

Warped discs are largely a myth, especially the thick vented ones. 

Have you checked the thickness of the discs?  Minimum is 22mm, as far as I remember. 

[Max Headroom]

Warped discs are largely a myth, especially the thick vented ones. 

Not on my Pug they weren't! I had to replace a string of them for warps possibly caused by a worn hub. Each time this was a run-out problem and not one of any deposits build-up. But if SAABs are different I can take that on board 

[Norfolk Jim]

Disks aren't bad for that aero. I replaced mine with a set from GSF which were Brembo originals and including pads came out to about £168 the whole set + 45 mins fitting time.

That got rid of my brake judder at 130k

[TomPaine]

Is the judder under hard braking at speed, or soft braking at low speed? If it's the latter and you're getting pedal judder it'll be the ABS cutting in due to a perished ABS ring/gaiter thing - common.

[idlerider]

Is the judder under hard braking at speed, or soft braking at low speed? If it's the latter and you're getting pedal judder it'll be the ABS cutting in due to a perished ABS ring/gaiter thing - common.

You may be right, Tom - certainly happens at low speed - just doesn't feel like the abs, though - more like slack somewhere. Last car that had this, turned out to have corrugated disks being amplified by worn suspension bushes.

[TomPaine]

You may be right, Tom - certainly happens at low speed - just doesn't feel like the abs, though - more like slack somewhere. Last car that had this, turned out to have corrugated disks being amplified by worn suspension bushes.

I know what you mean - it didn't feel like the ABS to me when it happened on my old 9-5 (hence the needlessly replaced front discs, doh!). Certainly have those rings/gaiters checked out before you shell out for anything more extensive.

[davidjay]

Worst case scenario - steering rack.

[idlerider]

Thanks, all. It's in for a big service next week, so I'll report back (probably wiser but poorer!).

[sgould]

Found the link about the warping myth

[idlerider]

Likely to be uneven deposits of brake pad material on the disc. Have you driven hard and then sat at the lights with your foot on the pedal?  Pressing the pad against a hot disc?

Know what you mean, but we have no fast roads here, little traffic - and no traffic lights in the entire county! I read the warped disc article though - fascinating; thanks for that.

[Norfolk Jim]

That link is fascinating Will.

SO what it says also is that a car used mainly in and around a city where brakes are used more often, in particular with sections of dual road that there is more tendency to get brake judder due to frequency of stops with brake pedal being kept down like at lights.............................whereas those in the countryside stand less chance of this happening.............. Makes sense as my last car never had it but this current one did and it was used a lot in and around London.

[Audax]

I'd say the opposite, brakes in London won't get used hard and will never get hot as you never go more than about 2mph, in the countryside you're far more likely to use the brakes hard and more often.

[sgould]

I agree.  I never had brake judder in London.  But I did when I worked in the home counties.  If you have driven around some twisty roads and had a bit of fun, got the brakes hot and then come down to the uphill halt sign on the main road and had to wait with your foot on the brake.

I could get sticky brakes on the run down to J19 of the M25.  It's a downhill spur.  It was a 70 mph road and it came to a give way at a busy roundabout.  Ditto J17.  17 to 19 was the original Watford and Rickmansworth by-pass.  The two ends were not used for the M25 itself.

[jmblack]

I'm having a problem with corroding discs due to lack of use. I'm doing roughly 80 mile round trip daily, mainly on motorway, so actually hardly ever use the brakes. They never really get shiny! I've a 95 estate diesel so with one passenger and little braking I'm never close to using capacity of brakes and do little more than tickle them. I need to make myself drive BMW style, charging up behind people and slamming on brakes.....