Archive of BMW Motorrad Club Cape (2006 - 2019)

The modification washers for the 1200 GS recall campaign was the right thing to use

Hi Alf

I have the 1150GS - does your advice still apply?  According to Shane the mount point has worn down with a raised bit where the bolt is in the middle, and the edges depressed.

If I get stuck perhaps I should bring the bike through to you?

regards

Charles

My discs sounded like a metal rubbish bin full of stones when I first got the bike.  Andy added only a few o-rings and total silence since!

It is a sure cure and more durable than o rings

I didn't know about these!  I'd also be interested in curing my problem properly without spending more thousands.  Let me know if and when you go please Charles.

This weekend I fixed the noisy rotors.  Here's how:

Neil Terry gave me some assorted thicknesses of steel sheet.  I bought some tools after seeing what the problem involved:

• 12mm steel drill bit (and a 10mm bit for backup/good measure - and yes, they are eye-wateringly expensive),
• assorted flat and round files, fine for dressing the aluminium mount points and tidying up the steel work

Take off the front wheel and put it on a milk crate to avoid damaging the rotors.

Milk crate work surface

The problem is that the loose rotors have worn away part of the hub that holds them in position.

Worn mount point

Close up

On the worse side, the raised section was 0.8mm high.  I had some steel sheet of .7mm which would fill the gap nicely.  The raised portion is where the bush between the bolt and the rotor touches the hub, but due to the oval hole in the rotor itself, and the range of movement of the floating rotor, the raised portion is not round, it is oval with a length of 16mm and width of 12mm.

Oval Rotor holes

Shane had warned me that whatever I use to fix the problem, the disk must be flush with the top of the raised bit.  With the fine flat file I very carefully removed the rough edges and burrs from each mount point and cleaned it up nicely.

Then, with the 12mm steel drill bit I drilled 5 holes in the .7mm steel sheet, and made the hole oval by drilling another overlapping hole 4mm offset.  With the round file I adjusted the size and shape of each hole so that it would fit snugly over the raised bits on the hub.  I cut each 'washer' out of the sheet with a coping saw, and then unashamedly ground each 'washer' into a more-or-less even shape with the rough end of a bench grinder and some thick leather gloves to protect my fingers from the grinder, the burrs and the heat.

Washer in place

I imagine that what Alf is talking about re 1200 GS recall washers, would be steel washers in the right shape to protect the aluminium hub from the rubbing of the steel rotor as the disc floats.  These would also help fix this problem once it occurs.

Anyway, when I reassembled the rotor and wheel, the rotor was firm and no longer rattles.  But, on the other side, the problem was harder to fix - the rotor was much less loose, which means the raised section is only 0.1mm high - too low for a washer.

So I tried to build up the gap with epoxy steel, using a big flat washer coated in copper-slip to press the epoxy into a flat of the right height.

Pressing a flat

Built up with epoxy steel

To avoid any epoxy steel getting on the flat of the raised section (which is where the bush rests), I put a thin layer of copper-slip on each raised section.  Copper-slip is important - it does not get soft and runny when hot, so won't eventually run onto the discs or brake pads.

Once the epoxy set, I put on the disc.  The five mounting bolts get blue loctite into the holes (apparently when applying loctite to a bolt going into a closed hole, one should put the loctite onto the thread in the hole, not on the bolt). 

Torque to 24Nm

24Nm is 24N at the end of a wrench that is 1m long.  Now 1N = weight of 101g, or 1kg = 10N about.  So 24N is about 2.4kg.  And 2.4kg at 1m is about 5kg at 0.5m.  So, I measure and assemble a wrench of about 50cm and put a 5kg weight on the end.  It is actually a lot looser than I would have tightened it by hand, and I can understand why - a bolt going into aluminium alloy can easily strip the threads.  Also, there is loctite involved and the forces are perpendicular to the bolts.

The Result

The brake rotors do not rattle at all.  It seems even a tensioner kit is unnecessary (saving of over R700).  My next concern was that somehow the rotors were out out alignment, but a short test drive and braking exercise showed that the wheel is quiet and the brakes are good.

Time will tell whether:

1. the new steel washers prevent the aluminium from wearing away further, and
2. the parts built up with epoxy last the distance and don't eventually crumble and leave the disc rotor wobbling or rattling.

Further investigation needs to be done around the 1200 recall washers and whether there is a permanent solution to the wearing of the rotor mount points.

After the 130 000km service at Atlantic, and with the front rotors no longer sounding like 'a rubbish bin with stones in it', Mr. Badger purrs along beautifully quietly, like a real BMW!

This problem and fixes are described on the Wild Dogs forum also