Front disc probs

[newbuild100]

Apologies if this has all been heard before on here !
Bike is a 2008 standard GS12 with 20k on the clock.
Symptons . .at low speeds,(when braking with front brake) im getting what feels like a warped front disc thru' the brake lever and the very slight "too-ing and fro-ing" of the bike itself.
Normally, id say this was a warped disc. But, Ive quickly checked each disc with a DTI and they are perfect (Besides which, they are "floaters" anyway).

I think Ive read/heard that the rear disc is somehow connected to one of the front discs. Whatever, im not getting the above when applying just the rear brake.

There is definite play with both front disc "bobbins". I can to and fro both discs around the axle, if that makes sense.
My local dealer says thats normal. It does seem excessive to me but i cant find any "limits" that BMW may have set.
I have however compared this play to a brand new GS (and even that had a very small amount of slap in both discs) Mine is far worse though.

The dealer also suggests that one or more of the brake pads could be not moving too freely (now this one I dont believe)

Im suspecting the worn bobbins but any more clues/opinions anyone ?

Thanks all

 

[G5RJO]

Try and run the bike down from 30 - 35 ish on the overrun only. NO BRAKES.

Do you fee the oscillation through the bars? Try a loose grip on the bars as well. It may not be the brakes at all.

I had exactly the same symptoms. It was the front tyre..... Conti trail attacks.

I had about 5 or 6 sets as they were on offer (I do big miles). Had to send all bar one front back. Conti' know there's a problem.

Roger.

 

[newbuild100]

No, tried all the above. No other symptoms really. Tourances fitted very recently but bikes always been the same, even before new rubber.

 

[Beemerman59]

If you're able to, go out for a ride but don't use the front brakes fot a few miles - just rely on ghe rear. Then stop and feel the disks to see if either are warm. If they are you might have sticking pistons in the caliper. I had similar wigh one side of one caliper - they weren't seized, I just had to take a little fluid out of the m/c.

 

[wust588]

Wheel bearings?

 

[comberjohn]

I've had a similar problem on a few bikes.
Worth checking for a sticky pad. Had a K1600GT last year with knackered wheel bearings and it just had a slight weave when slowing down.
My problem was that I don't use the brakes hard enough. I tend to anticipate more than most riders and brake pads last a long time. Ok, I'm a driving instructor.
My theory is that you get a residue on the disc that feels like a high spot if you don't get the brakes hot enough.
I found the cure is to take a few higher speed runs and give the brakes a good workout. Get them hot.
In my experience, always use BMW or Brembo pads. Not from eBay. Been there...

 

[Wilsdorf]

On some of the BM's the pistons are a type of plastic material that degrades or disintegrates if damaged. I had a new kit fitted on my R1200 that had a similar feeling.

 

[tanneman]

The R1200GS does benefit from a brake calliper clean every now and then. Sounds like a sticky piston in the calliper. As already been mentioned.

 

[Bendy toy]

Dirt and clag gets under the seals a strip down early enough lets you refit the old seals. Wise move because BMW only sell seal & piston kits at £60 a caliper.

 

[Slipperyeel]

On some of the BM's the pistons are a type of plastic material...

Plastic? Or do you mean they have a 'plastic' coating? The latter sounds more feasible!




Sent from my SM-N910F using Tapatalk

 

[boatman]

I used to get this on this age(ish) of Gsa. On a few occasions.
Turned out to be the front brake pads seizing partially
Solution turned out to be, remove pads ,grind about 10 thou off the ends ,then put on a wee chamfer. A slight smear of coppaslip n Bobs yer proverbial

 

[Bendy toy]

Some brakes have phenol resin pistons

 

[Wilsdorf]

Plastic? Or do you mean they have a 'plastic' coating? The latter sounds more feasible!




Sent from my SM-N910F using Tapatalk

The Pistons on my R1200S had started to disintegrate - they were replaced with a standard kit, which fixed the problem - I was amazed to see the holes, and then be able to chip further bits off with a screwdriver!

 

[Slipperyeel]

Some brakes have phenol resin pistons

Interesting. I can guess the benefits, just surprised they'd use it on mass production bikes/cars (instead of an exotic/high cost vehicles).

Thanks for the info


Sent from my SM-N910F using Tapatalk

 

[Bendy toy]

I don't know 100% if BMW use resin caliper pistons. But piston & seal kits at £60 per side suggests they do. Rear brake (two rather than four piston) costs £20 for seals only.
Hope cycle disc brakes now use phenolic resin. A good downhiller can hammer the brakes.
https://my.cardone.com/English/Club/Products/Brakes/Protech/FAQ/caliperq.asp

 

[Duall]

My bike of the same year did the same thing when I first bought it (used with 10k on the clock). Thinking it was the discs and then checking the price of them I didn't bother with it and kept riding it like that. That was a few years and about 20k's ago and it slowly got better. I still have the same brakes even the pads and go figure, it works great with no vibrations...