Brake judder - opinons please
Discussion
M-SportMatt said:
Warped discs are not that rare.
Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-mythsHeavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
M-SportMatt said:
Warped discs are not that rare.
Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
That sounds like the exact circumstance where transfer of friction material from the pad to the disc is most likely.Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
james_gt3rs said:
M-SportMatt said:
Warped discs are not that rare.
Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-mythsHeavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
He is of course looking at race cars ( in 40 years of professional racing ) with top notch braking equipment designed for racing temperatures on adequately cooled cars......and theres no junctions or traffic lights. Apart from that his points hold up well.......for race cars.
Whereas I am looking at reality....
Take a shed value mondeo...add some cheap motor factor chinese discs and some rock hard 'performance' brake pads et voila, bake at 300 degrees for two minutes for warpage.
I've seen it with my own eyes and had it skimmed.
General Fluff said:
I have significant brake judder, noticeable at speeds of 60+.
My Merc did that - discs looked OK on the outer face, but the inner was horrible. Seems odd to me, as the piston is on the inside, but apparently it's pretty normal.Once rust has set in it rubs away the pad so that part of the pad doesn't touch the disc - so no amount of heavy braking will clean them up. My brakes started to feel very "dead" as well, so I got them all changed.
M-SportMatt said:
Warped discs are not that rare.
Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
Absolutely not! The amount of heat required to warp a disc is well outside the realms of road car usage.Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
r11co said:
KevinCamaroSS said:
The LEAST likely is warped discs because this is as rare as hens teeth.
Not true. It's quite common on certain makes/models of cars where the brakes are on the limit of spec for a vehicle of that weight/performance.Mostly, in my experience, you are looking at cause and effect with the run-out being the effect mainly as said by others due to uneven distribution of pad material. The heat required to warp a disc will generally not be seen in everyday road use, and usually only on very cheap aftermarket brands/quality.
If an OE or OE quality disc was warped it would be warped on first press of the pedal (which they never are as they are manufactured beyond the tolerance required).
Usual culprits are improper fitting / cleaning of the hub face or worn components not restricted to: Suspension bushes/joints, calipers, bearings, top mounts. Even the wheels themselves and/or balancing (loss of weights) can produce the same 'feeling' on braking.
Confirming run-out with a DTI gauge and replacing discs and pads often just buys you time before the same happens again. What has caused the run-out is what you need to find out.
If an OE or OE quality disc was warped it would be warped on first press of the pedal (which they never are as they are manufactured beyond the tolerance required).
Usual culprits are improper fitting / cleaning of the hub face or worn components not restricted to: Suspension bushes/joints, calipers, bearings, top mounts. Even the wheels themselves and/or balancing (loss of weights) can produce the same 'feeling' on braking.
Confirming run-out with a DTI gauge and replacing discs and pads often just buys you time before the same happens again. What has caused the run-out is what you need to find out.
KevinCamaroSS said:
M-SportMatt said:
Warped discs are not that rare.
Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
Absolutely not! The amount of heat required to warp a disc is well outside the realms of road car usage.Heavyish car. with load and passengers ...prolonged downhill braking to a junction......sit there with foot on brake for 2 mins at traffic lights.
Warped
As the last post says though warping can just be the effect of another problem such as hub run out, sticking calipers etc etc..where the disc WILL be warped but not due to any normal heat cycle
You can argue long and hard but i've seen numerous warped discs over the last 20 years.
KevinCamaroSS said:
The LEAST likely is warped discs because this is as rare as hens teeth, most cases of 'warped discs' diagnoses is actually brake pad deposit. To warp a disc would require temperatures far higher than that possible on road cars.
Not that rare - I've had warped discs on a brand new car. Confirmed as warped discs and replaced under warranty.... It happens.r11co said:
General Fluff said:
It's a 335i if it helps.
Check the caliper piston isn't sticking. I had a similar problem (330i) after rear pads were changed and it turned out to be dirt having crept into the piston bore when it was wound back to fit the new pads. Leads to all sorts of weird brake behaviour because of the 'self drying' feature that automatically applies the brakes gently periodically.If the piston is sticking don't bother faffing about trying to clean it. Good quality re-furbed calipers are cheap if you source them properly.
Fore Left said:
I had the same on my 330i. Horrendous vibration at 50mph+. Turned out to be a sticking rear caliper. Take the car for a good run, stop and flick water on the disks. If any boils, that's the culprit.
A constant vibration or only under braking? I don't understand why a sticking caliper would cause a vibration but what to I know? I don't think that's the problem anyway as they turn freely on the drive.Thanks for all the comments, though I'm none the wiser currently. I'll either replace or skim and report back. Probably skim as they still look like new on the rear.
General Fluff said:
Fore Left said:
I had the same on my 330i. Horrendous vibration at 50mph+. Turned out to be a sticking rear caliper. Take the car for a good run, stop and flick water on the disks. If any boils, that's the culprit.
A constant vibration or only under braking? I don't understand why a sticking caliper would cause a vibration but what to I know? I don't think that's the problem anyway as they turn freely on the drive.Thanks for all the comments, though I'm none the wiser currently. I'll either replace or skim and report back. Probably skim as they still look like new on the rear.
If the caliper isn't moving freely it drags on the disc and gets very hot, when the disc, piston, pad backing etc etc gets hot it expands which causes the brake to drag more, this causes it to get hotter.... and then you leave the motorway and stop at the lights, the pad welds itself onto the now stationary disc leaving a nice patch of friction material on the disc, rinse and repeat...
General Fluff said:
A constant vibration or only under braking? I don't understand why a sticking caliper would cause a vibration but what to I know? I don't think that's the problem anyway as they turn freely on the drive.
Thanks for all the comments, though I'm none the wiser currently. I'll either replace or skim and report back. Probably skim as they still look like new on the rear.
Before you do.... Have a go at the re-bedding in.... 10 HARD applications of the brakes (60mph down to 5mph, straight back up and do it again)...Thanks for all the comments, though I'm none the wiser currently. I'll either replace or skim and report back. Probably skim as they still look like new on the rear.
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