1150 GS FD bearing removal questions

br30205

Generally speaking from experience rarely does the shimming change between bearings (both sides) but you never know and checking is very important IMO.

The 18 different shims are more for compensating for machining tolerances of the FD case. Bearings themselves are built to extreme close tolerances (unless you buy Chinese no name)

In my experience, back when I worked as a BMW mechanic, transmissions and final drives all required shimming. Every one of them. Some from brand new. This was well back in the day of /5, /6, /7 motorcycles.
The large ring gear and needle combination of bearings on the output side is shimmed to control the thrust loads on the large bearing. The shimming of the pinion side is primarily to adjust the gear engagement.

This may be helpful

http://www.advrider.com/forums/showthread.php?t=905243

Remember there was a bearing PN change a couple years ago.

The bearing I replaced in my FD was from prior to the change and failed at ~100k miles, it had .6mm of shim in the cavity. I'm assuming it was shimmed properly because it went so long without trouble. I did not determine what the preload would have been with that bearing and shim combination.

Its replacement is the new PN and took only .25mm of shim to set the preload at .071mm, as measured with a dial indicator, this bearing has gone ~30k miles without issue. The housing obviously hasn't changed, but there appears to be a huge difference in the bearings between designs.

This is a place I'm a bit confused. I thought shim 4 in the attached set the pinion clearance and shim 2, working through the large bearing, set the tapered bearing preload when the cover is bolted in place. With that understanding I'd select a different shim 2 if I found the preload incorrect.

Would I be doing wrong? Besides maybe crushing the outer race, how does shimming affect a roller bearing?

I just rebuilt my FD at 40,000. The steal was leaking but no other issues. I figured that I would check the factory shim job. Original bearing measured at .40mm, and preload of .05-.1mm and you get .45mm shim. BMW had a .70mm shim! After cleaning the big bearing, you could feel the wear sso I decided to replace and ordered a .45mm shim. After installing the new bearing from BMW(14yrs newer bearing so if there was a update, i'm sure I got it) and rechecked endplay. Exactly the same as factory at .40mm so out it all together and crossed fingers. So far I've clocked 2600mi and it's perfect. Good luck with yours and definitely check and reshim! If I every have to replace the bearing again, if bearing thickness measures the same, I'll just throw and go!

The large bearing has (for a bearing) a pretty loose lateral tolerance. I suspect that unless you grossly overshim the large bearing, the small bearing won't be loaded to any real degree.

Ball bearings don't handle thrust loads well and wear the edges of the race. Therefore the reason for proper preload adjustment. Shim number 2is the one you change!

This is correct if the crown wheel ball bearing (#3) is the only part replaced.

If you change the roller bearing (#5) on the RH side, the backlash must be measured and the shim washer (#4) may need to change.

I would change the RH roller bearing only if it shows signs of wear.

I would (and this is what I always do) change both bearings and re-shim, so that you only get your hands dirty once :)

The roller bearing can be supplied from bearing shops for ~ 15$ around here.

Dan.

I've measured the assembled thickness of the old tapered and compared to the new and found the dim. to be identical. Never had to mess with the small shim.
Shiiming was checked on the FD and found to be the same as original and in spec.


I've

+1

All the rolllers in the #5 bearing and the cup are pitted/spalled so it will be replaced. I haven't removed the crown gear from the cover to inspect the ball bearing but it rolls fine and there doesn't appear to be any looseness.

Look closely at the outer race where the balls ride. Beginning signs of failure is erosion and pitting of the surface. The bearing will spin nicely with this condition only to fail later.

It's off! All this shimming talk has me scarred so I'm taking it to a trusted shop to service the FD. I don't have micrometers to do it right. $180 plus parts seems like a good price so I don't have to mess with it for a while. I drained the FD and found lots of sparkly bits, but no chunks. The pivot bolts were a b*tch to get off. I heated the crap out of them and they would not budge. They eventually gave way but they were tight!

That's a lot of debris in the oil. I would be tempted to at least split the FD case and have a look before turning it over to a shop for repair.

Curiosity is killing me. I just might have to crack it open!

How much of that is magnetic?

I can't think of any source for yellow metal in the final drive, and it definitely looks like brass in that photo.