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Once more my FD bearing failed

2K views 42 replies 14 participants last post by  Voyager 
#1 ·
I don't know how to start this. I don't know if I should repair the d@mned FD once again or set the LT on fire and sit further away and enjoy the spectacle.
I had rebuilt this FD twice. Once used the same shims and it failed 1100 Km later, the next time I saw the video with the shims calculation, used the 0.04 of a mm as it resulted and the LT did 38000 Km without any problem. It even did a 3400 Km trip from Greece to Dalmatian coast, Venice, Napoli, Pisa, Florence, Rome, Pompei, Bari and then back home loaded at the limit. My buddy's LT did not feel anything on this trip. It was also carrying the same load.
I opened it today and found that the *** bearing is still rotating well but the balls cage failed. Tomorrow probably I will remove the bearing from the crown and cut it half way to find out where the balls were running. I will send photos.
Now see below my findings till today.
 

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#2 ·
Man sorry about your horrible luck...

riding oildheds since 1995, broke everything that can be broken, still zero failures on any of my final drives (five of them at the moment all from 11GS (11/33)

I hope somebody figure out the issues, nothing more bottresome that a bike you can not trust..
 
#3 ·
I am not one of the FD gurus on this site but if it failed in 1100km the first time, it had to be way over shimmed. I think you got closer to what it needs the second time but still not quite right. It is a difficult measurement to take and get right as I have done 3 myself with 2 different measuring methods. So far, so good but I haven't checked it this season yet but I am hopeful for nothing but fuzz on the magnet again. I would recommend you do it again and repeat that measurement several times. Do you remember if your shim pack put you on the high side, middle or low side of your calculation? Are you using the required C3 spec 19 ball bearing and not the less expensive C1 spec which is not accurate enough to be used in that application? I couldn't tell if the taper bearing had any pits from the ball cage bits or not but it looked like it made its way in that bearing.
 
#4 ·
Don't lose heart, I believe it all comes down to the correct shim adjustment. A single row ball bearing shouldn't have too much positive loading in any one direction. I suspect that you just didn't get it quite right. I have rebuilt some pretty big gear boxes on large steel cutting band saws. These boxes are more like a big final drive with just a worm and crown gear. Most of them have tapered roller bearings that have to be actually torqued up to specification. In the case of a single row ball bearing you need to make sure that the balls run central to the inner and outer races while eliminating slop in the action. My advice would be to go to your local bearing supply store and talk to them about the required specification for the specific bearing that has failed.
Another important thing to check is that the outer race of the bearing is being held snuggly in it's housing and not able to spin or have any side to side movement because this will cause the bearing to be unevenly loaded.
 
#5 ·
That first bearing must have really been over shimmed to fail in only 1100 KM! You are getting closer now though.

You might check the diameter of the other end of the shaft where the tapered roller bearing should have its bore tight on the shaft. There have been some terrible engineering and workmanship issues when these were manufactured and assembled.:(
 
#6 ·
I will reply to all of you here.

when I did the 1st repair I asked a trained BMW mechanic in a dealership in Athens Greece. He told me by word, "whatever you do, DO NOT CHANGE THE SHIMS THICKNESS". He sounded very positive and shouted as well. I followed his advice and felt it running bad at 1100 km, opened it again and cut the bearing in half. I saw that the balls were running on the side of the U. Then followed the youtube video and calculated the shims to 0.04 instead of 0.08 mm it was initially. After this repair I did 38000 km. I believe I did good. After I remove this one I will cut it again and update you on where the balls run.
Throughout this 38K run I had put a temp sensor on the FD oil filler plug. The maximum temp I noticed when I was driving two up + loaded in Italy with 39 degC Amb was 60 degC. Even if the sensor had a 10 degC failure it was at 70. I wouldn't say it suffered much at this temp.

Yes, the bearing was a ***, C3, made in Germany. Printed on the outer ring.

Here are the two cage pieces that broke off the bearing. The mechanic that did the repair 38K ago said it is probably a part quality failure and not the shimming calc.
 

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#7 ·
To say that the mechanic in Athens is incompetent is being kind. The second mechanic is almost certainly wrong as well. I’d say this is most likely still a case of too much preload.
 
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#12 ·
I have a freshly rebuilt Final Drive from a 2002 LT , professionally built by Rubber Chicken Racing (Tom Cutter). PM me if interested. Had as a spare, sold the bike.
 
#14 ·
Welcome to the forum Ryan. I am always interested in peoples research on the FD bearing failures so where did you read that? It is not a shielded bearing so it should have no issue with oil penetration in cold starts as the lower 1/4 of the bearing is sitting in the oil and should carry the oil with it as soon as it starts to turn.
 
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#18 ·
You mean this one? From the MaxBMW parts fiche. Always had better luck here than at realoem. You can find the seal at the same place.
 

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#21 ·
All, finally we removed the failed bearing and it seems it suffered from operation and load. Maybe I loaded the gal too much but I believe you do the same too. I have a wife that rides with me. This can't be changed. From what I found is that our shimming was very correct as the bearing balls were running in the channel center. The rest looks that the inner ring suffered from wear. How would you justify this?
See my findings below and also the bearing printed data.

My humble opinion is that when BMW designed this bike they thought: "and what about the FD? what do we do?"
Someone replied: "Herren(in German) we have too many FD's on the shelf from smaller bikes to get rid off, why don't we just bolt them on the LT?"
>:):laugh::laugh::laugh:
 

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#22 ·
That is ugly. Dug up some specs on load. Do you know how much load you are placing on the bike and if over the limit, by how much?

Unladen Weight with Full Tank 378.5 Kg / 833 lb
Dry Weight 345 Kg / 759 lb
Permitted Total Weight 600 Kg / 1321 lb

Available capacity 221 Kg / 488 lb
 
#28 ·
Sorry for the troubles you have encountered with this final drive. I'm totally unqualified to give you advice since I don't own a "K" bike, haven't even ridden one. However, I'm an incurable "tinkerer," with enormous curiosity and have taken the time to read your posts and what I believe is sincere attempts to help from others on this forum. However, to this point, it seems that everyone is concentrating on the bearing, and other perishable components, installation methods, etc.

I'm wondering about the final drive housing itself? Is it possible that the housing and bearing "seat" machining is out of spec? I've sold and serviced some of the most expensive name brand industrial tooling in existence. Pumps, conveyors, robots, powder coating systems, tooling, etc. Try as they might...sometimes things get by Quality Control Patrol.

Perhaps it would be good to get your hands on another housing and have a good machinist (not me) do a thorough micrometer comparison check on your housing? Although I spent years selling precision measuring tools, I use them so sparingly myself, I would have to refer to a manual every time I pull one out of my tool chest. Someone who uses them daily, could save you a lot of trouble by confirming the housing is worth rebuilding and not the problem. I hope you solve the issue as I'm sure we could all learn from the solution.:bmw:
 
#37 ·
The below links are some interesting reading for those concerned about your final drives. Most of the numbers were gathered by CharlieVT (Curtis). The last two links shows the numbers. Just remember, most of these surveys were done before 2007.


https://www.bmwlt.com/forums/k1200lt/68639-should-i-fix-final-drive-isnt-broken.html

From April 2006:
If you look at the rear drive survey the numbers would tend to point towards the fact that it helped. There were 30 failures reported in 02, 3 in 03, 1 in 04 & none so far in 05 or 06 models.

Complete thread here:
https://www.bmwlt.com/forums/k1200lt/7929-17-ball-rear-bearing.html

From November 2006:
Actually, our statistics say differently. Pre'03 LTs had the most failures. Pre'05s had less than the previous group. And now, '05 and '06 LTs have less than 5 reported failures. BMW has done SOMEthing...even if they've never admitted to the issue.

Complete thread here:
https://www.bmwlt.com/forums/k1200lt/16417-report-final-drive-failures-nhtsa.html

Survey Numbers from October 2005:
https://www.bmwlt.com/forums/k1200lt/523-rear-drive-survey-results.html

Read post 12 $ 13 here:
https://www.bmwlt.com/forums/k1200lt/59708-one-year-more-prone-final-drive-failure.html
 
#38 ·
It sure would be great to see an update of this, but that likely is a lot of work. Also, the last comment in the thread said the survey had no answer for “FD has not failed” so I am not sure what the percentages of failure are referenced to, unless the comment is incorrect in regards to the survey. Given the mileage dependence of the failures, it is not surprisingly that the older bikes had had much higher failure rates. It would be interesting to see failure rates by both year and mileage, but again a lot fo work for little gain at this point in time.
 
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