Rear Brakes getting oily

[MichaelSydney]

I have progressively lost rear brake efficiency on my '83 R65. On removing the rear wheel I find the shoes and drum are both oily, though not dripping, just enough to prevent friction!

This happened before a few weeks back and at the time I thought it was because I had over-greased the splines. There does not seem to be oil streaks radiating from the splines so I don't think it likely the source is that main oil seal. Now I suspect the O rings on the brake actuator shaft allowing the escape of final drive lube.

I have looked but cannot find a specification for these O rings. Can anyone suggest a suitable size and type please?

[montmil]

Two possible sources for the gear oil that's contaminating the brake drum and shoes:

Your examination of the brake shaft o-rings is the primary failure point. Yhe small o-rings are the only thing retaining the final drive gear oil. Withdraw the shaft and you see a gaping space directing opening into the final drive crown and pinion gears. This design was supposed to be an improvement by BMW engineers.

Second suspect is the large oil seal within the Cardan cover. The seal's thin 'lip' rides on the smooth portion of the spline gear shaft and is subject to wear.

I'll have to review my records from my o-ring purchases and see if there is a size listed. Stand by...

[D Mann]

Bobs BMW has them listed as 10x2 at $0.51 each. I did mine last year and they work fine.

[montmil]

Bobs BMW has them listed as 10x2 at $0.51 each. I did mine last year and they work fine.

Yeppers. I checked with Bench Mark Works in Sturgis... the other Sturgis in Mississippi and 1981> use the 10x2 brake can o-rings.

Use caution when installing the little boogers. The shaft enters a bore that has a very sharp edge. Lube the o-rings and carefully work them into the bore. If they get cut, they are worthless. Cheap bits so order an extra or two. I call that anger management.

[Bob_Roller]

Get a few extra seals, in case you cut one during installation .

Also when you remove the brake cam shaft, you will see a few extra grooves cut into the shaft, they  don't any seals, just the deep square bottom grooves at each end of the shaft are for seal installation .

[suecanada]

Second Bob's caution of putting the o-rings in the deeper square grooves.
Not those shallow rounded ones. Just for interest sake..how many shallow rounded grooves does the shaft have on your bike? And how many square grooves??

[montmil]

There will be two square-bottomed grooves for the o-rings -both as the last machine groove on either end. The shallow grooves, how ever many you may have, are there to catch gear oil splash from the final drive case and lubricate the steel shaft to aluminum bore.  

Earlier Airheads had a tubular bushing for the brake shaft that needed to be greased regularly. This chore was often neglected and lead to excessive wear and gear oil leaks into the brake drum/shoe area. Mottorad's attempt to save us from ourownselves.

[MichaelSydney]

Thanks everyone,  really appreciate the info and cautions.

I have a few little jobs to do around the back of the bike so will get some O rings and sort this out..

[Luca]

Mine takes 3 o-rings and they only lasted about a year.  I don't think I nicked anything, as they did work for a full season.  I heard rumors that there were some machining errors with some of the brake cams in the early 80's that led to insufficient pressure being put on the o-rings:  True story?

Either way, I removed both brass brake cam bushings and had a one piece stainless bushing made that goes between the "cardan" cover and final drive.  BMW later went (back) to this design.  Unfortunately, the later BMW bushing didn't fit my final drive.  It was too small on the outside to press fit.

[Burt]

Michael,

You will have to toss the two brakes shoes and buy new ones after they become oil contaminated as they will put oil back on the inside of the drum, leading to the same problem with the brakes.  

It is best to clean everything with white spirits as it does not leave an oily film on cleaned components.  All the brake shoe contact surface areas must be 101% dry but you probably already know this.  It would not hurt to run some say 400 grit aluminium oxide sandpaper around the inside of the drum to clean up any irregularities.

Cheers, Dave.

[Kookaburra]

Burt says you will have to throw oiled brake shoes away to avoid recontamination.  I saw a thread earlier where someone suggested you could boil the brake shoes up and skim the oil off the top. Anyone tried this and with what result?

[Tony Smith]

Burt says you will have to throw oiled brake shoes away to avoid recontamination.  I saw a thread earlier where someone suggested you could boil the brake shoes up and skim the oil off the top. Anyone tried this and with what result?

You should throw them away, but they are back brakes..........I would clean them with white spirit (or brake cleaner, or petrol, or shellite, or kero) and re-use them. In fact the brakes in my R65 were condemned units from my wife's bike for that very reason.

[Bob_Roller]

Gave the cleaning method a try a few years ago, used a parts washer at work, hot soapy water , after 6 hours of washing, one of the friction linings disbonded from the shoe .

[suecanada]

I had good luck with the boiling method (my kitchen!) then Rob Valdez suggested going over the shoes with 60 grit (sandpaper only) and 220 grit sandpaper for the linings. Never the greatest of brakes on my bike but as good as probably possible. At least locking up the rear wheel is not a huge concern!! But can be done....when it's raining for instance a skid could result.

[Luca]

I also suffer from slightly oil permeated shoes.  The feel isn't as good as it should be, but I can still lock up the rear wheel on dry pavement.

I had bought a new set of shoes after my o-rings failed.  Decided to de-grease as best I could when the second batch of o-rings failed.  LS shoes run about twice as much as the already-expensive regular variants.  One of these days when I get around to it, I'll see if the local truck spring and brake company can re-line my shoes.  Still kicking myself for tossing my first set of shoes... that's valuable aluminum if it can indeed be re-lined.