Front brake mystery

[Roadcaptain]

I notice my offside front brake disc was loose last week so ordered new bolts, washers and bobbins, all fitted and disc was good again, also changed pads while I was playing. today disc is loose again and some of the washers seemed to have either disappeared or flattened out. I will get some more washers on Monday but any ideas why this might have happened?

 

[Slipperyeel]

Presumably you're referring to the wave washers? If yes, then either they were duff or there's something not right with the assembly and/or components. When the disc is mounted properly there should be some free play. The wave washers take up the slack and keep the disc central. If you're assembling it and the disc is rock solid then something is amiss. Got any photos of the parts you're describing?


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[Roadcaptain]

no photos as I am at work, I assembled as I took them apart, i.e washer, bobbin, bolt, bought all parts from motorworks. I will have a better idea when I take it apart again, but need to get some washers first.

 

[Slipperyeel]

But you got all new bobbins and washers. Have you offered them up to the old ones to compare and check they're identical? Just a thought.


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[Kenny Rodkiss]

Look and see if the mounting posts on the wheel are not worn.
The disc can wear away the alloy so make sure part 5 is fitted, can be retro fitted to wheels that did not originally have them.
Bolt, Bobbin, Wavy washer, flat washer, disc, flat washer and wheel.

 

[Grizzly]

Confusion?

Kenny,
Your illustration above is confusing me
It shows items 1, 2, and 3 in the correct position and as fitted as original parts - item 5 is the "new" part fitted to rectify hub boss wear, it is 8mm bore and around 20mm outside diam. and 1.0 thick.
Item 4 - I do not understand, never seen this item fitted, don't understand it's function?

Maybe I'm missing something- but if not then this illustration will cause problems.


Cheers..................Grizzly

 

[mspenz]

I'm with you on this one Grizzly and I should have added those 20mm washers when I changed my discs recently , will do so when I fit my TKC70s soon though..
I'm sure that M/Works were doing them but you can probably source them elsewhere?
Part No.4 doesn't make sense to me either, where did this diagram come from?

Mike.

 

[Kenny Rodkiss]

I had a rubberised washer on each side of the disc.
See this old post, http://www.ukgser.com/forums/showthread.php/268295-Rattling-front-discs
You would have to have part 4 or the wavy washer would be damaged by the sharp edges of the disc mounting slot??

 

[Roadcaptain]

Update
the caliber pistons were sticking making the disc compress the washers on every revolution of the wheel this must have made them brake and fall out, callipers now freed up I hope washers fitted waiting for tomorrow to test her out.

 

[Steptoe]

When the disc is mounted properly there should be some free play. The wave washers take up the slack and keep the disc central. If you're assembling it and the disc is rock solid then something is amiss. Got any photos of the parts you're describing?


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The above info is wrong.
You should feel no discernible play.

There will be play, but you shouldn't be able to feel it at all by hand.

 

[Grizzly]

Kenny,
Never seen anything with the rubberised washers or item4 between disc and wavy washers
I've just checked old (original) bits from my 2001GS:-

Disc......................................................................5.00 mm thick
Bobbin length from under head to mounting face...........6.00 mm thick
Wavy washer..........................................................0.30 mm

So, disc + wavy washer = 5.30 mm, leaving 0.70 mm "float" possible on a bobbin - which sounds about right?
So can't see how you can fit another washer in this 0.70 mm and still have a "floating" disc?
You parts must have been "specials" or modified Kenny?

Cheers..................Grizzly

 

[Pekkavee]

A picture from Max BMW Parts Fiche

Pekka

 

[Slipperyeel]

The above info is wrong.
You should feel no discernible play.

There will be play, but you shouldn't be able to feel it at all by hand.

Steptoe, this doesn't match what i have on my bike right now (and they're working perfectly) nor my old GS on which i replaced all the washers, bobbins etc.

If you pull the disc sideways then there is exactly that, discernable movement and they are not rock solid onto the wheel hub. What are the wave washers for of there isn't supposed to be some movement of the disc? Can you explain?





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[Grizzly]

Hey Pekkavee, your just making things worse - because the Max BMW fiche shows the wavy washer on the outside of the bobbin rather than under the bobbin flange against the disc!!!

Cheers.............Grizzly

 

[Kenny Rodkiss]

Had to go and check to make sure I wasn't cracking up,

Bobbin is 5.5mm and discs were 4.5mm new with a minimum of 4mm.
Wavy is 0.30mm and part 4 is 0.45mm so
Disc 4.5 + 0.30+0.45=5.25 leaving 0.25 of possible sideways movement.
These were all standard fittings on my 2001 1150gs except for number 5 which I added later to protect the disc mount posts.
This part does not alter the amount of float or clearance available to the disc.

There are longer bobbins from the rt which uses a thicker disc than the GS, 5mm instead of 4.5mm.
But the parts here are the standard parts from my bike

 

[Grizzly]

Very Interesting

Well Kenny, well done for digging your old bits out AND taking photies. We seem to have another mystery of BMW production then?

My 1150GS - which I still have - was registered 1st Sept 2001
The original discs, as measured today, were 5.00 mm thick and stamped Min 4.5 mm, It has "Bremb0" calipers and is non-abs. I didn't realise BMW mixed up the spec so much? How does anybody know they're fitting the right parts

Cheers....................Grizzly

 

[mspenz]

It seems that there are so many variants fitted to different models / different years

My 04' servo with linked brakes has 5mm discs so a 1mm washer would flush off any worn alloy and keep things inline but adding anymore would be too much.
Kenny, you say that the RT uses longer bobbins for the thicker 5mm discs but any other GSs I've seen also use a 5mm disc , as long as we all know our own bikes then all we can do is offer impartial advice

Roadcaptain, what bike are you working on?

Mike.

 

[Kenny Rodkiss]

Well Kenny, well done for digging your old bits out AND taking photies. We seem to have another mystery of BMW production then?

My 1150GS - which I still have - was registered 1st Sept 2001
The original discs, as measured today, were 5.00 mm thick and stamped Min 4.5 mm, It has "Bremb0" calipers and is non-abs. I didn't realise BMW mixed up the spec so much? How does anybody know they're fitting the right parts

Cheers....................Grizzly

Well I dinnae ken, mines was an eary 2001 blue and white GS no abs.
I do remember trying out some galfer discs but they were 5mm thick and obviously would not fit with my 5.5mm bobbins, that's how I found out that the rt had thicker discs and longer bobbins.
Never knew the GS came with a thicker disc as standard?
Looking on parts list there seems to be a change in brake discs Nov 2001?
Dunno.
I would imagine Steptoe will have seen every combination that is going and can maybe confirm??

 

[Roadcaptain]

mine is a late 2003 with servo abs, definitely just bobbins and wavy washers. look her for a 70 mile test ride today and seems ok now.

 

[Steptoe]

Steptoe, this doesn't match what i have on my bike right now (and they're working perfectly) nor my old GS on which i replaced all the washers, bobbins etc.

If you pull the disc sideways then there is exactly that, discernable movement and they are not rock solid onto the wheel hub. What are the wave washers for of there isn't supposed to be some movement of the disc? Can you explain?





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I have explained.. You shouldn't be able to feel any play. The discs aren't fixed absolutely solid but you shouldn't be able to feel any play by hand. Just because both your bikes had discernable play doesn't mean that's how they should be.
They aren't like that from new so why should they be like it later in life.
The same applies to the 1100/1150 and 1200 models.