Brake judder after a week of no use....
Discussion
I've put this in GG rather than a marque specific forum, as I've heard of another motorist, with a different car who has the same symptoms.
Following battling through the snow and ice in the lead up to christmas my car was then left on the driveway for 7 days, unused. On my first drive after this short period I noticed the brakes with juddering quite severely.
The effect after a few drives is less pronounced, but definately still there. I would discribe the feeling as if the discs are warped, or uneven friction - noticed that they had got very rusty, but that seems to have cleared almost completely (on the visible parts anyway). I can feel the judder through the steering wheel, especially if I loosen my grip, when the steering wheel rim visibly shakes.
Any ideas what has happened here and why?
Following battling through the snow and ice in the lead up to christmas my car was then left on the driveway for 7 days, unused. On my first drive after this short period I noticed the brakes with juddering quite severely.
The effect after a few drives is less pronounced, but definately still there. I would discribe the feeling as if the discs are warped, or uneven friction - noticed that they had got very rusty, but that seems to have cleared almost completely (on the visible parts anyway). I can feel the judder through the steering wheel, especially if I loosen my grip, when the steering wheel rim visibly shakes.
Any ideas what has happened here and why?
Surface rust after a car is stood is normal, normally resulting in that grinding sound which should wear off after gentle use. Even drive along and gently apply handbrake to clean up the rears.
Sounds like you have used the car a fair bit though and they do sound warped with them juddering.
Sounds like you have used the car a fair bit though and they do sound warped with them juddering.
Definetley corrosion under wear the pads been sat on the disc if you've got open spoked alloys normally makes it worse. Should clean up after some use but if not will need new discs. Merc's were quite bad for this if they were washed on the forcourt and left for a couple of weeks would allways end up like this.
They do rust but what you have is hard lumps where the brake pads have been touching the disc while it's not been used. Easy fix if it doesn't clear itself after a couple of days, jack it up, take wheel off, get some coarse abrasive paper (not sand paper). Look at the disc & you'll either see or feel the hard lumps, normally the same outline/shape as the pad, rub them off with the abrasive paper.
RacerMDR said:
i have exactly this problem on my BMW. I only left it for 2 days but it had severly been salted.
I'm hoping it is the pads being damaged from the rust on the discs - and eventually it'll settle down
if not it is going to be an expensive service
Mine's a BM too, so am really hoping it isn't the common wishbone bushes. Cannot believe it is though, as it started suddenly and after a period of no use, rather than developing over time. Also I don't get any knocking or lateral movement when on rough surfaces or over speed bumps, etc.I'm hoping it is the pads being damaged from the rust on the discs - and eventually it'll settle down
if not it is going to be an expensive service
Your discs have Pad imprint which is an area where the salt has eaten into the disc causing a rough patch. In some cases this area will wear off with no problems. In your case it sounds like the pad imprint area has changed the surface hardness and is now wearing at a different rate to the rest of the disc, causing DTV (disc thickness variation) this will cause major judder when braking. The best way to sort this is to find a garage with a PROCUT ON-CAR BRAKE LATHE. This machine will minimum skim your discs whilst still on the vehicle removing the pad imprint area and eliminating DTV. Cost should be about £40 - £50. It is advisable to replace the pads, but if pads are reasonably new you can remove them and clean up by rubbing them on emery paper on a flat surface. A quick search on the internet will soon find a garage near you with this equipment.
TOPHOOKER said:
Your discs have Pad imprint which is an area where the salt has eaten into the disc causing a rough patch. In some cases this area will wear off with no problems. In your case it sounds like the pad imprint area has changed the surface hardness and is now wearing at a different rate to the rest of the disc, causing DTV (disc thickness variation) this will cause major judder when braking. The best way to sort this is to find a garage with a PROCUT ON-CAR BRAKE LATHE. This machine will minimum skim your discs whilst still on the vehicle removing the pad imprint area and eliminating DTV. Cost should be about £40 - £50. It is advisable to replace the pads, but if pads are reasonably new you can remove them and clean up by rubbing them on emery paper on a flat surface. A quick search on the internet will soon find a garage near you with this equipment.
Sorry to be skeptical but "changed the surface hardness" - now I'm no metallurgist but I believe this to be nonsense.Contrary to most opinions here I believe the problem isn't rusting - its more likely to be some of the pad material has effectively broken off the surface of the pad and welded itself to the face of the disc - this can actually prevent corrosion in the spot where the pad has been sitting (as its not as exposed to the elements as the rest of the disc surface), but can leave a "high spot" on the disc which is a combination of pad material still stuck to the disc and/or a spot which didn't corrode as much as the rest of the disc.
In either case if there is an effective height difference at one point in the disc then it will need to be levelled - you could try sandpaper, but could create as many problems as you solve, most likely an extended period of driving and hard braking will sort the issue and if not then as above getting the discs skimmed is a cheaper option than new discs (assuming there is a safe enough amount of disc material remaining - check manufacturer specs and ask the skimmer how much they will remove). There are other brands and methods of skimming available than the one obviously being advertised above.
I thought that I had this on the Lexus - before the bad winter by the way - and carried on regardless. Turns out that I had screwed the disks, the pads were badly worn and the calipers were cream crackered too! Covered under warranty and the difference now is like light and day - but if you have an issue, might be worth getting it checked anyway, I managed to ignore things and screw them up!
GreigM said:
TOPHOOKER said:
Your discs have Pad imprint which is an area where the salt has eaten into the disc causing a rough patch. In some cases this area will wear off with no problems. In your case it sounds like the pad imprint area has changed the surface hardness and is now wearing at a different rate to the rest of the disc, causing DTV (disc thickness variation) this will cause major judder when braking. The best way to sort this is to find a garage with a PROCUT ON-CAR BRAKE LATHE. This machine will minimum skim your discs whilst still on the vehicle removing the pad imprint area and eliminating DTV. Cost should be about £40 - £50. It is advisable to replace the pads, but if pads are reasonably new you can remove them and clean up by rubbing them on emery paper on a flat surface. A quick search on the internet will soon find a garage near you with this equipment.
Sorry to be skeptical but "changed the surface hardness" - now I'm no metallurgist but I believe this to be nonsense.It will also explain why there is no such thing as a "warped" brake disc.
jonnynine11 said:
Definetley corrosion under wear the pads been sat on the disc if you've got open spoked alloys normally makes it worse. Should clean up after some use but if not will need new discs. Merc's were quite bad for this if they were washed on the forcourt and left for a couple of weeks would allways end up like this.
Sill are I fear 
Electric Beaver said:
GreigM said:
TOPHOOKER said:
Your discs have Pad imprint which is an area where the salt has eaten into the disc causing a rough patch. In some cases this area will wear off with no problems. In your case it sounds like the pad imprint area has changed the surface hardness and is now wearing at a different rate to the rest of the disc, causing DTV (disc thickness variation) this will cause major judder when braking. The best way to sort this is to find a garage with a PROCUT ON-CAR BRAKE LATHE. This machine will minimum skim your discs whilst still on the vehicle removing the pad imprint area and eliminating DTV. Cost should be about £40 - £50. It is advisable to replace the pads, but if pads are reasonably new you can remove them and clean up by rubbing them on emery paper on a flat surface. A quick search on the internet will soon find a garage near you with this equipment.
Sorry to be skeptical but "changed the surface hardness" - now I'm no metallurgist but I believe this to be nonsense.It will also explain why there is no such thing as a "warped" brake disc.
I'm no expert & I don't know what causes the lumps under the pads sometimes after a vehicle hasn't been moved in a while, but if I were to hazard a guess I'd say rust between the pad & disc causes a little bit of pad, normally around the edges, to stick to the disc. These are easily removed with course abrasive paper which I have personally done in the past.
There's always the possibility that I could be wrong & salt has eaten into the disc, but a couple of pound for a bit of emery paper & having a look first before getting your disc skimmed/new discs would seem the easy option to me.
I will explain the surface hardness factor. When you have pad imprint the moisture trapped against the disc by the pad forms a small pocket of corrosion which has eaten into the disc surface. viewed with a magnifying glass this will appear as lots of little black dots. The CORROSION is harder than the material than the disc is made of which is why you get a different wear rate.
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