got a problem on the brakes on my bmw come about recently. steering's getting shakey again, and when i touch the brakes the judder is pretty
intense!
when the car slows down though, and i just touch the brakes to come to a nice gentle stop, i can feel the brake pedal move up and down, and this
coincides with the speed of the car, seems like it goes up and down with every turn of the wheels.
this was posted a few days ago
http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml#
which suggests there is no such thing as warped brake discs, so thats my thoughts out the window. so what could it be? i can't beleive i can feel
the pedal move up and down, something would have to be REALLY out of shape for that!
Real or perceived, I changed the discs on the wife's Alfa the other week for exactly the same symptoms - touch wood she's not felt it since?
Well if you read that article through it'll tell you what exactly it is, how to stop it in the future and also how to remove the build up on the discs.
Although I think once it gets to moving the pedal is going to be quicker to put a few set of discs and pads on anyway. Then read the article on how to stop it in future
Had it on an old car once, and changing the discs (Under warranty) solved the problem.
Don't believe everything you read on the web. There is a whole lot of pee written about brakes disks and brakes in general.
(1) You can get brake vibrations from discs without the disk being warped. This caused by the surface of the discs --- Fords were very prone to
this in the 1970s to the extend that Girling made special replacement brake pads with an abrasive top layer to clean up the discs.
(2) Warped discs (and oval brake drums) really do happen, and this is the most common cause.
From your description it sounds like warped disc as being able to sense the pedal going up and down at slow speed is a definite pointer to the disc
being physically warped.
BMW use old fashioned fixed opposed piston calipers rather than floating calipers.
With a a warped disk this type of caliper will tend to give a more pronunced kick back through the hydraulic system at slow speed than a floating
caliper.
However be aware your description of the symptoms also fit a split ABS ring --- not all ABS faults trigger the ABS warning light.
A visual check on the ABS rings would be easy enough to do when replacing the discs.
[Edited on 21/9/10 by britishtrident]
I know on the string of Audis I've had the rear discs don't see enough braking force and can start to cause issues if not attended to...
Most often from not getting a thorough workout they can build up material from the pads.
It sounds strange but I've also had an issue with worn front wishbone bushes causing brake judder. Check those out while your under there.
Also (as you probably know) it's essential to ensure that the mating surfaces behind the disc are as clean as possible to ensure the runout is
within limits. You'd probably notice this from the start however.
[Edited on 21/9/10 by SeaBass]
quote:
Originally posted by SeaBass
I know on the string of Audis I've had the rear discs don't see enough braking force and can start to cause issues if not attended to... Most often from not getting a thorough workout they can build up material from the pads.
It sounds strange but I've also had an issue with worn front wishbone bushes causing brake judder. Check those out while your under there.
Also (as you probably know) it's essential to ensure that the mating surfaces behind the disc are as clean as possible to ensure the runout is within limits. You'd probably notice this from the start however.
[Edited on 21/9/10 by SeaBass]
One thing - don't skim the disks, just buy new.
I had a skoda once (don't laught) and the disks vibrated from when i bought it second hand. Took it back, they skimmed up the disks and within 50
to 100 miles it was warped again. New set of disks cured the problem.
quote:
Originally posted by britishtrident
quote:
Originally posted by SeaBass
Check those out while your under there.
[Edited on 21/9/10 by SeaBass]
Yeah worn suspension bushes can magnify brake vibrations