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Damn! Another final drive bearing failure!


JayJay

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The good news is: the problem wasn't the driveshaft (a $1000+ part, non-rebuildable without extraordinary effort).

 

The bad news is - Yup, another final drive crown bearing failure.

 

Background: I have just over 70K miles on my '09 RT. Good miles, overall dead reliable on the road. Have never had a second thought about heading out.

 

I have a trip coming up late May, and I want to get the scheduled 72K service out of the way before I head out. It's a major major - all the 6K, 12K and 24K scheduled items are in grand alignment. So with the alternative working on honey-do projects, I thought I'd check the brake pads and rotors to see if they were ready for replacement too. While I had the rear pads out to check the pad thickness and clean up the caliper, I rotated the rear wheel. Got a gritchy sound and feel, and some clunks while rotating it. Ruh-roh.

 

The first thing that came to my mind was crown bearing failure, as after the outer seal that's been the most common mode, with driveshaft (universal joints) second. I have a dial indicator and the proper fittings, so I did the wheel perimeter deflection test that the RepROM outlines. Permissible is 1.0 mm deflection, mine measured out at 0.33-0.43 mm, well within tolerance. Hmmm.

 

So I dropped the final drive off the driveshaft as if I was going to lube the splines. Driveshaft felt good and tight, but the gritchiness (highly technical term, if you have to ask you won't recognize it when it happens) was still there in the final drive. Given that the perimeter deflection was within spec, and the roughness was inside the final drive, I wasn't willing to preclude pinion or ring gear failure. I didn't want to expend the effort and time to look into it myself. So, call to the dealer for an appointment.

 

In the meantime I had to continue to ride - after my bicycle, my motorcycle is my primary transportation. I normally wear earplugs and as such hadn't heard anything unusual, but I decided to not wear them a couple of times. Sure enough, once I listened for it I could hear the pulsating. And I could feel the roughness as well (with the clutch pulled in on a smooth street).

 

Got it back from the dealer yesterday (had a 2007 R12GS as a loaner, their newest one - my shop refers to their loaner fleet as "vintage"). Turns out that it was indeed a crown bearing in early failure. Others have reported that their failed crown bearing came out in pieces, often in the drained lube. Mine didn't, it looks perfectly normal but upon rotating it you can definitely feel the roughness. And the bike now rides nice and smooth.

 

The pocketbook damage wasn't unreasonable: three hours and parts, home for ~$550, which isn't too bad for a major repair. First major failure I've had (I don't count fuel strips, those are kind of pesky like black flies).

 

Path forward: I think the pass-on from this story is to be sensitive to what your bike is telling you. In hindsight I think I was feeling the vibrations for quite a while but thought it was just needing a tuneup (my bike is very sensitive to TB sync for smoothness). Wrong, again 20-20 hindsight.

 

So the next time you have your bike up on the center stand, take a moment to rotate the rear wheel. You may hear only brake pad drag, but if you hear some thunking or feel something that is the slightest bit rough, you may be in early failure. Especially if your bike is "middle age", like mine is. Not too difficult to pull the pads, or pull the caliper off (not such a bad idea anyhow, to check whether the sliding pins are free), and that will remove the sound and drag of the brakes so you can isolate the final drive. It should be smooth.

 

Should this have happened? Considering that this generation of final drives was originally touted to be "maintenance free", not only no but hell no. I have never had a differential or axle bearing failure on any automobile I've ever owned, and some of them have been real POSs. And frankly, I expect better from BMW. But history has shown us that the crown bearings on the final drives of BMW 1100-1200 series of several iterations may be prone to early failure. I don't think the hex/camheads are failing like the 1100/1150s, LTs or early K-bikes, to be sure, but not zero. I'm glad I caught this one early so I didn't have to return home on a tow truck from the middle of nowhere. And I do feel better for having looked closely at the driveshaft, it's reported that those universal joint failures sneak up on you slowly.

 

And after all that, the brake pads and discs are fine, plenty of life left. And there's an added benefit I discovered this morning while riding in to work: the driveline backlash is noticeably reduced (checking and adjusting pinion-to-ring gear clearance is part of the renewal procedure), leading to smoother shifting.

 

JayJay

 

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Afternoon Jay Jay

 

On your 1200 final drive, the crown bearing runs in it's own (separate) sealed chamber so the bearing parts never show up in the drained gear oil. (this is different than the older 1100/1150 final drives)

 

You are correct in that there are a lot less 1200 final drive failures so there was some progress made there.

 

From what I have (personally) seen on the 1200 final drives is while there are less total failures, the ones that do fail seem to fail again in a lot of instances.

 

Now that you have a new crown bearing check the "cold" rear wheel play again & if no play found there is a good chance you will see another failure at a later time. (on the 1200 you actually want to see a bit of wheel movement cold)

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Afternoon JayJay

 

No hurry, if you went 72K on the original then you have a good chance of at least going close to that on the 2nd bearing.

 

It's the 12K to 25K early failures that are the bad ones as the chance of another 12K to 25K failure is a real possibility.

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Afternoon JayJay

 

No hurry, if you went 72K on the original then you have a good chance of at least going close to that on the 2nd bearing.

Yeah, that was kind of my thinking, but thanks for reinforcing it. But it would be good to have the play measurement anyhow as a baseline to watch as time progresses. The bad bearing still feels good and tight, it's just rough, like maybe only a few of the balls failed, or that there's a surface failure at only a small portion of the race.

 

Like I said, I'm just glad I caught it early and could deal with it on my schedule rather than having it fail on me on the road. To get from California to most anywhere except north I need to cross Nevada, and there's an awful lot of nowhere out there. Pretty (I really like the desert), but lonely.

 

JayJay

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Guest Kakugo

Vibrations is what saved me from getting stranded.

I am always blown away from how much you people pay for FD bearing replacement (I paid mine 240€ including taxes, BMW dealership, genuine parts) but, hey, at least sometimes it's good to live here. :rofl:

 

Mine was replaced at 60000km. At 90000km I had a very similar vibration coming back again so I had the bike checked: I simply lack the sensitivity to check clearances myself. :P

Turned out it was the front wheel bearings. Given the roads I often travel upon, they lasted too long. Curious how the vibration felt so similar.

 

And about the bearing itself... mine had some clear signs of corrosion. I should have taken pictures, but as usual forgot.

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