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Discussion Starter #1
I have 82K miles on my '02 LT and changed the rear crown bearing at 48K before I went on my Alaska/Arctic Circle trip. I can now notice slightly more rear wheel rock when checking per the factory shop manual during my 12K services. It's only a hair looser than my '02 K1200RS which only has 16K miles on it. I can't seem to find the tolerance listed in the manual anywhere? The check is described, but the acceptance limit is not indicated. Anybody know the tolerance at the outer rim edge?
 

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old1951 said:
I have 82K miles on my '02 LT and changed the rear crown bearing at 48K before I went on my Alaska/Arctic Circle trip. I can now notice slightly more rear wheel rock when checking per the factory shop manual during my 12K services. It's only a hair looser than my '02 K1200RS which only has 16K miles on it. I can't seem to find the tolerance listed in the manual anywhere? The check is described, but the acceptance limit is not indicated. Anybody know the tolerance at the outer rim edge?
Is the play in the wheel bearing or the final drive pivot bearings.

I may stand corrected but there should be no play in the wheel bearings since they are preloaded to prevent side-play.

Now lets see what the experts say....

Roy
 

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Zero is correct, but make sure it is not the entire drive that is moving. With that many miles I would suspect the drive pivot bearings have worn. They have a tendency to beat notches in the races and that allows side to side movement.
 

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Discussion Starter #4
Interesting?

I quote from the BMW repair manual "maintenance" section, Group 00, page 00.67; "Checking rear wheel bearing play by tilting wheel (Inspection III). Tilt the rear wheel to and fro across its axle." No tolerance is given and yet they do not say there should be zero lash. At 600 miles my bike had a very slight rock, this has grown slightly since then. I teach friends how to service their K1200LT's and I've never seen an LT (20+)with zero lash. I'm using the terminology defined by BMW. Others may use other terms. Considering that an LT uses a 17" wheel, the amount of play felt at the outside circumference of the tire would be very, very small at the bearing itself. I just thought someone would know for fact?

There is separate check for swing arm bearing wear, this is determined by a different method (not wheel rocking) and this can be adjusted per Group 33 instructions. My bike has no detectible swing arm play to date. I religously change my drive oil on a 6K mile interval and it's looked the same on every change after the first 6K service. At the initial 6K it looked awful! My rear drive fears got the best of me prior to my Alaska trip in 06 so I changed the bearing at 48K.

My intent is to not be too concerned. With 82K on the clock the bike performs absolutely great (especially since changing my suspension to Ohlins). Personally, I believe the first visible sign of a drive failure problem would be an oil weep from the rear main seal. It doesn't take very much out of alignment to make a large seal like that leak. I've never seen the slighest indication of oil in this area.

If anyone has "for fact" data on this wheel tilt tolerance, I'd appreciate the info.

Happy riding to all.

I'm headed off for a 2-week Canadian Rockies trip, two-up with Unigo in tow in late June. I don't intend to make any mods to the rear drive prior to the trip.

Just thought I'd ask the collective. There are lots of opinions out in the ciber vapor. I've never had a rear drive failure, but I have replaced the crown bearing once. My plan has always been to change the crown bearing on a 50K mile interval.
 

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Discussion Starter #5
My apologies to John et al!

After playing with my rear drive rock a little more I discovered the if I rock the rear wheel to and fro as BMW states (the manual does not define where on the wheel to grab) from the front and rear along the driveshaft line I get a very small amount of play. If I rock it top to bottom (which is difficult because its hard to get your hands up on top under the rear seat) I have no play. A worn Crown bearing or taper bearing in the rear drive would show movement regardless where you rocked the wheel. The front to rear rock infers that the entire drive assembly is moving ever so slightly indicating some slight wear in the floating needle bearing races as John stated. After reading John's it make all the sense in the world!

As always, we can learn from others. I should have realized that the tech writer who wrote the manual verbage probably missed the key tilting location point that the engineer was explaining.

Thanks to all.
 

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I don't think this is complicated... unless you make the mistake of making it complicated. ;)

There is a spec for axial and radial runout limits for the rear wheel. This spec isn't about the bearing, it is about the wheel. If you have ever rebuilt a spoke wheel, you understand this pretty well. WRT to a cast wheel, the spec basically relates to whether the wheel is servicable after damage.

With respect to play at the rear wheel with the wheel properly mounted to the final drive, there should be no play detectable by feel with the hands. Putting a micrometer on this assembly makes no sense.

If there is detectable movememt of the wheel when it is mounted to the final drive, the source of that movement needs to be identified. I could be the final dive, but if it is the final drive, you are likely to be experiencing roughness in the ride, and oil leakage. A more likely source of looseness is the pivot bearing which have a history of developing play. If this is the source of looseness, the bearing should be replaced IMO. I have read many reports of looseness at this point being "fixed" by re-torquing" the pivot bearings. That will eliminate the play for a while, but will fail to identify the original cause of the play which is probably degradation of the pivot bearings (a common finding). Play at the pivot bearing is best repaired by removing the wheel, the final drive, and inspecting the pivot bearings. At this point you can anticipate replacing the pivot bearings.
Another source of play at the rear wheel could be the swing arm mount, but I haven't read reports of this and consider it an unlikely source of play at the rear wheel.
In summary, ANY axial or radial play detectable by hand at the rear wheel is an indication of a problem and the source needs to be identified.

Addendum: In a subsequent post, the term "lash" is used. Just to make sure we are talking about the same thing, all bikes (all vehicles for that matter) have some driveline lash. This is a consequence of spacing and wear between gear teeth.
Axial play, as detected by grabbing the wheel at the 12 and 6, or 3 and 9 o:clock positions and feeling for movement, would not be described as "lash" IMO. This would simply be axial play and the limit is zero detectable by hand. You would be able to measure some with a micrometer, but I don't know that there is a spec ( I don't think so), and the spec would be pretty meaningless since that play would be the sum of several sources.

2nd addendum:
Quote "My rear drive fears got the best of me prior to my Alaska trip in 06 so I changed the bearing at 48K."
Was the preload for the new bearing checked prior to assembly, or was a new bearing just installed with the original shims?
I am currently rebuilding another final drive that has indications that the drive is on its second failure. Replacing a bearing without checking for preload and just using the original shims is asking for trouble IMO. However, a preemptive rebuild done this way probably has better odds of long term survival than does a rebuild of a failed final drive without doing preload measurement. Again just an opinion.
 

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Discussion Starter #7
The movement has been identified and it's in the pivot bearings. I may play with this once my summer trip is behind me.

None of my concerns had anything to do with the radial runout tolerances of the rear wheel (spoke or cast).

As far as getting into the final drive shim issue, I'll pass on that debate because there are way to many folks who claim to be experts out there.

82K miles on the clock and my original drive is humming along nicely with a new bearing at 48K (just for insurance) which was probably not really necessary. Many harp the shim issue. Been through too many rear ends of all kinds to count, including VW's which are so similar its scary.

I'm fine with being called lucky. Then again maybe I know something about drive setups too? My original question was what was the tolerance? Sure be nice if BMW simply stated "zero" based on shim preload.

Ride safe
 
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