Discs - Warped? Definitive answer? Any theories?

[Deleted account 211025001]

Well, my ’05 GS is now on it 4th set of replacement front discs and a rear.

The first discs were replaced at 6k due to squealing and very slight juddering felt through the bars (mostly only felt under light ‘town speed’ braking).

These were then replaced at 15k due to the re-emergence of juddering.

I then replaced these with cheap pattern ones when the same symptoms reoccurred at 28k. Pretty much from day one there was no improvement. So I replaced the rear disc with an EBC item, still no improvement.

So, at just over 34k I bit the bullet and fitted EBC discs and replaced all bobbins, washers and bolts.

After about 500 miles the pulsing was back and, now at 36k it is probably worse than I have experienced before. It is also different in so much as it now happens at high speed/hard braking but is intermittently non existent at lower speed. In fact, if I ‘very’ gently apply pressure and build braking it’s as smooth as a smooth thing. If I brake normally it’s there.

Now I know there are plenty of theories around re. the front brake issue. I’ve spoken to my dealer and he admits there is a known problem. He also says that the latest GS’s with their different mounts are not immune. He can’t suggest anything other than replace the discs.

I’ve oft wondered if it’s because the disc has no carrier and is mounted directly to the wheel – get a wheel out of tolerance and that could be the problem, who knows?

The thing is, the fact that my problem appears intermittent, going from no pulsing at all to pulsing so hard that a pillion can feel it could point to some other issue; pulsing servos/ABS? Dunno, I’m none the wiser?

I’ve checked wheel bearings and fasteners and all seem ok.

Anybody have a definitive answer as to what’s going on, any new theories?

Andres

 

[julio100]

My 05 had 4 pairs of discs on the front and 3 rear discs
no explanation for the front discs apart from a modification which seemed to cure the squeek and the warp effect
the rear disc fault was found to be the hub out of line which was replaced and then no fault
hope this helps

 

[Deleted account 211025001]

My 05 had 4 pairs of discs on the front and 3 rear discs
no explanation for the front discs apart from a modification which seemed to cure the squeek and the warp effect
the rear disc fault was found to be the hub out of line which was replaced and then no fault
hope this helps

Mmm, that sounds like the mod I had done when my discs were first replaced - different mounting washers to eliminate the squeal and help the discs 'float' better (at least, that was my understanding of what was done?).

Andres

 

[RickG]

Mine started juddering when quite new but after 10k the juddering had gone completely and has been fine for 75k. I can't see how warped disks would do this as they can't un-warp themselves? The frequency of juddering is quite low too and I never had any pulsing at the lever which would in my view indicate a warp. I've always wondered if the whole front end can set up an oscillation triggered by something to do with the brakes - a bit like the chatter old jap' bikes could produce when hard on the brakes. Perhaps a systematic measurement of disk run-out when new, old, hot and cold may show up something - at least determine if any changes are taking place? I'd be seriously tempted to check the run out of the disk carrier too (ie the front wheel casting) just for fun. Can you borrow someone else's front wheel to see if that makes any difference?

 

[Big Nick]

One guy posted that changing the front wheel solved his warping discs so that might be worth a try

 

[(RIP) Bin Ridin]

Can be caused by holding brakes on at lights after hard stop, leaving patches of brake material on the disc.
My car (durango) has given me awful brake pedal judder going down a long steep hill and using the brakes a lot, well known for the flimsy discs to warp due to uneven heating but they seem to settle back when cool.

 

[ebbo]

I wrote this up about a year ago - http://www.ebbo.org/front_brake_fix.php

But my brakes are just starting to pulse again, not bad yet but when I get around to it I’ll be checking for run-out caused by incorrectly machined disc mounts.

And I’ve heard a new front wheel can fix the issue too, further pointing to incorrect machining of the mounts...

 

[EURTRAF]

Andres
Try thoroughly cleaning both front disks with brake cleaner and see if the brakes still pulse.
My 1100S failed its MOT due to supposed warped disks (dial fluctuating by more than 3 segments) they then thoroughly cleaned both disks and suddenly no pulsing and bike passed fine.

Of all the people who have had 'warped disks' how many have actually been checked on a purfectly flat surface rather than just 'pulsing'

Steve

 

[smartrider]

I had a 1200RT in 2005 that the dealer replaced a few sets of discs before realizing it was the wheel that was not true. once the wheel was replaced no more problem.

Each time the discs were replaced they were O.K for a while, if I remember correctly they were always O.K for about 2000 miles before the problem came back.

 

[ebbo]

Andres
Try thoroughly cleaning both front disks with brake cleaner and see if the brakes still pulse.
My 1100S failed its MOT due to supposed warped disks (dial fluctuating by more than 3 segments) they then thoroughly cleaned both disks and suddenly no pulsing and bike passed fine.

Of all the people who have had 'warped disks' how many have actually been checked on a purfectly flat surface rather than just 'pulsing'

Steve

Hmm, I'll give the discs a real good clean up and see how it is,

 

[cookie]

Mine started juddering when quite new but after 10k the juddering had gone completely and has been fine for 75k. I can't see how warped disks would do this as they can't un-warp themselves? The frequency of juddering is quite low too and I never had any pulsing at the lever which would in my view indicate a warp. I've always wondered if the whole front end can set up an oscillation triggered by something to do with the brakes - a bit like the chatter old jap' bikes could produce when hard on the brakes. Perhaps a systematic measurement of disk run-out when new, old, hot and cold may show up something - at least determine if any changes are taking place? I'd be seriously tempted to check the run out of the disk carrier too (ie the front wheel casting) just for fun. Can you borrow someone else's front wheel to see if that makes any difference?

that sounds like loose headraces on a normal front end. dunno if telelever bikes do the same, and i certainly don't know how it fixed itself. adjusted during a service perhaps?

 

[rick]

My front discs were changed due to warping at 6976 miles, again at 15452 miles and a third time at 21498 miles. At this third set the front wheel was also changed under warranty and I've had no problems since (well not with the discs anyway). Mines an 05 GS with over 51K on it now.

I believe the wheel manufacturer at this time went bust.

I'd be having a word with my dealer and arguimg that for this to keep happenning there must be an underlying fault causing it, which was there from new and that BMW should give you a front wheel as goodwill.

 

[RickG]

that sounds like loose headraces on a normal front end. dunno if telelever bikes do the same, and i certainly don't know how it fixed itself. adjusted during a service perhaps?

Funnily enough a slight judder was picked up on the 600 mile service, though I'd already noticed it myself and thought 'here we go' as the demo bike I'd test driven was exactly the same. The stealer said see if it got worse and if so they'd fix it on the next service. Thankfully it sorted itself out over the next 3000 miles or so and I've never looked back.

It would make sense if, like car disks that have been parked up so long they develop a rust patch where the pads are in contact, the judder is caused by a patch of contamination which eventually wears off as the disk cleans up. However, nothing like this was apparent on my bike which is constantly used.

I've once had exactly the same problem on a car which was due to a 'bad' tyre which only became out of balance when hard on the brakes when it would shake like crazy even though it was balanced OK by a tyre shop. Swapping it to the rear 'fixed' the problem straight away, presumably because it never saw the same loads as when on the front

Bizarre.

 

[theop]

from all the opinions above, I d be tempted to go for the "wheel not running true" one... Change the wheel and see..

btw, my front discs squeal in town since the beginning 12k miles ago, but no warping/pulsing...

Another point, your problems have occurred at 6k miles, 15k, 24k, 32k.... These seem decent mileage gaps esp for a rear disc, no? My rear brake at 12k miles is on its 3rd pad set and the disc abt to fail its MOT.... Oh, and I rarely use the rear brake pedal, well, never actually....

 

[Deleted account 211025001]

Another point, your problems have occurred at 6k miles, 15k, 24k, 32k.... These seem decent mileage gaps esp for a rear disc, no? ....

Yer kidding.

Not unheard of on some 1200's but hardly 'decent mileage gaps'


Looks like another chat with my dealer and see if they can look at the front wheel as I've pretty much exhausted all other routes

Andres

 

[Deleted account 211025001]

Just a thought - anybody has this on spoked wheels or is it just happening to cast wheels?

Andres

 

[skywalker]

Come on then when's the poll going to start? Ooh whose had discs or whose not had discs.
I think it all went wrong when Nestle bought the "Yorkie" formula and they tasted different

 

[rick]

Just a thought - anybody has this on spoked wheels or is it just happening to cast wheels?

Andres

My wheels are cast.

 

[dxwalt]

I have excactly the same problem and still have no solution. Surely BMW must have some idea what the issue is. Has anyone had the problem with the new style disc mountings, I believe they give more float.

 

[jontym]

Just had mine (05 27,000 miles)m.o.t'd today,advisory note ,slight judder from front discs.Thats the 3rd bloody set!!!!!