LS final drive/brake question

[tvrla]

A while back I installed a taller final drive on my 83LS from an R80 - 3.36.

Recently it started leaking so I pulled the wheel today to take a look. There was a bit of aluminum grit in there and closer inspection found the brake shoes trailing edges had been rubbing on the hub. The cam end of the shoes had migrated outward.

I looked on the parts fiche and that screen is worthless! The brake cam isn't even pictured, and it took me forever to locate the seal, which was pictured in the wrong place.

Does the LS have a special brake cam due to the different brakes to prevent the shoes from migrating? Was there a washer attached to the end of the shaft?

I'm thinking the metal filings may have caused or contributed to the seal failure - if it didn't just fail from old age. But it is leaking - it's the one visible right behind the splines on the left side.

[Luca]

from MAXBMW:
R65LS: 22       35 21 1 454 836       REAR BRAKE CAM (from 09/80)      0.37       1        $85.96
R65   : 22       35 21 1 454 836       REAR BRAKE CAM (from 09/80)      0.37       1        $85.96

The LS has taller shoes, longer shoe springs, and a bigger drum.  Everything else should be the same.  The shoes shouldn't move laterally because of the way they fit around the pivot pin in the front.  The aluminium could be the backing plates for the shoes if you see no other damage.

And I think there is a washer between the business end of the cam and the inside face of the final drive.

Was your rear brake way out of adjustment?

[nhmaf]

I'd have to pull my wheel off again to check.  
I know that the brakes shoes themselves are different, but I hadn't noticed that the cam was different.

We may have to get some folks to post up pics of theirs as well for comparison.

[Luca]

But it looks like the R80s had a number of different cams in them.  Haven't found one that matched.  What year was the donor?

[tvrla]

The donor was an 81-4 - same style as the 3.56 I swapped out.

Yeah, the brake was out of adjustment, so it's possible it could have walked because of that.

The bike was pretty rough when I got it and there was something odd about the rear brakes - forget now what it was. They didn't fit right and I had to heat them up with the propane torch and massage them. So I guess it could have been due to that as well.

I cleaned everything up really well and even cleaned up the seal surface. A new seal won't arrive till late next week - Max has them for ten bucks, but everywhere else it's $20 - so you might want to snag one now. Anyway, it doesn't seem to be leaking now. I needed to ride it so put the wheel back on and after 50 miles today it's staying dry. So who knows? Maybe it's fixed. But I'll definitely be checking up on it to make sure the shoes are staying put if it's not leaking any more.

[Luca]

While you're at it you might want to replace the o-rings on the brake cam.  I ruined a $140 set of OEM LS shoes because of those three little o-rings.

Fortunately bmw2valve.com (I should be their spokesman) has aftermarket shoes for half price.  I was able to get OEM at half price from e-bay.

If the final drive housings are the same, maybe the R80 bikes had a different cam profile?  Can't seem to figure a good reason why they're not the same part  [smiley=undecided.gif]

[tvrla]

I'll bet the different cams are due to changes/upgrades made along the way. The final drives are the same. It would be nice to sleeve the hole to prevent that oil leak.