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Thread: final drive failure data

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    Registered User f14rio's Avatar
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    final drive failure data

    "Enemy fighters at 2 o'clock!...Roger, What should i do until then?"

    2010 r1200r, 2009 harley crossbones, 2008 triumph/sidecar, 1970 norton commando 750

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    Benchwrenching PGlaves's Avatar
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    Final drive failure on a BMW. We've never heard of that. It must be an urban legend started on the internet.

    More seriously - those 328 entries (I didn't try to count same bike multiple failures of which there have been some) represent a.16% (16 hundredths of 1 percent) of the approximately 204,000 new BMW motorcycles sold in the US since 1993.
    Paul Glaves - "Big Bend", Texas U.S.A
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    Registered User mneblett's Avatar
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    Quote Originally Posted by PGlaves View Post
    Final drive failure on a BMW. We've never heard of that. It must be an urban legend started on the internet.

    More seriously - those 328 entries (I didn't try to count same bike multiple failures of which there have been some) represent a.16% (16 hundredths of 1 percent) of the approximately 204,000 new BMW motorcycles sold in the US since 1993.
    True, but 1993-on doesn't provide insight into the crush of crown bearing failures that became prominent starting ~2000.

    The significant increase in FD failures -- which, in hindsight, appear to be a problem with poor quality assembly (terrible supplier shimming of the bearings), not a fundamental inadequacy of the design -- seemed to coincide with the introduction of the K12LT. The reason I say this is that while the K12LT had the lion's share of the failures, other bikes (RT's, GS's) also started to occasionally fail in this time period.

    At one K12LT group gathering in the early 2000's, a BMW regional rep stated that the failure rate (crown gear bearings and seals (seals usually being taken out by a disintegrating bearing)) was *4%* -- a frankly stunning number for a mass-produced vehicle from a quality manufacturer (imagine the reaction to a 4% rear axle failure rate in a car line!).

    The only good news in this is that it appears the total redesign of the final drives has finally addressed this issue (as I understand it, by re-arranging the bearing layout so that shimming is no longer a critical operation). Seems that most of the relatively rare issues today are outer seal-related, and even that should go away if BMW adopts the K16's new closed outer end design across the model line.
    Mark Neblett
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    Registered User greenwald's Avatar
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    Talking

    Quote Originally Posted by f14rio View Post
    Word to the wise - before you get stoned by the corporate faithful, this is a site well known on this forum.

    Don't get me wrong - important data - in fact, I'm number 316 on a list that only started in 2001 and obviously doesn't include every FD failure. My Final Drive puked a few months ago @ less than 49,000 miles, despite exemplary maintenance. The FD issue is much bigger than many prefer to believe, and stats are constantly being disputed or creatively interpreted.

    It's just that this is a nerve that's been stepped on quite a bit lately, so be forewarned - some stone throwers are fairly accurate!!

    If you're bound and determined to liven things up, you might want to start an oil or helmet thread?!
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    Cam Killer marchyman's Avatar
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    Quote Originally Posted by mneblett View Post
    True, but 1993-on doesn't provide insight into the crush of crown bearing failures that became prominent starting ~2000.
    The FD was re-designed with new K bikes and the '04 R1200GS. The Big Hole FD doesn't seem to suffer from the crown bearing failure in nearly the numbers as the oilhead FDs. The Big Hole FD does have it's own failure modes.

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    Survivor akbeemer's Avatar
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    I put the over or under for the number of posts to this thread with in the next 72 hours at 85. That is I would if betting on line were okay.
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    Registered User mneblett's Avatar
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    Quote Originally Posted by marchyman View Post
    The Big Hole FD does have it's own failure modes.
    Agreed -- although after the initial GS issues with insufficient interference fit, and the early seal issues which have tapered off with each model year, it appears that the frequency of issues is far lower than in the past, and that BMW AG has actually been fairly successful in finally getting the bugs out of the new design. At this point the failure rates appear to have dropped back down to the rare-but-statically-impossible-to-eliminate level.

    For me, it's simple: (1) the final drive on new bikes is no longer an issue for me (I'm not concerned at all about the FD on the K16 I have a deposit on); (2) if I was buying a used early-mid 2000's RT or LT, first thing I'd do is remove the final drive and ship it to Tom Cutter to have it inspected and shimmed *right* so I could forget about the issue and enjoy the ride.
    Mark Neblett
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    Benchwrenching PGlaves's Avatar
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    Quote Originally Posted by mneblett View Post
    True, but 1993-on doesn't provide insight into the crush of crown bearing failures that became prominent starting ~2000.
    OK Mark, I'll play

    I used 1993 because that is when they introduced the R1100RS - the first Oilhead. But if you would prefer I'll use 2000 as the start year. In that case the 328 cases represent .27% (27/100 of one percent) of the approximately 120,000 new BMWs sold in the United States.

    Even that understates the case though because BMW at the highest levels has admitted it might be as high as 2% failure - meaning 98% don't fail at all.

    Believe me I understand those final drives and their failures. If only it were so simple as being shimmed improperly. While that may account for many or even most of the cases it fails to account for those caused by improper machining the diameter of the hub, overloading the motorcycle, use of out of spec. improper lubricants, serious road hazard impacts, etc.

    I sent a couple of failing but not yet failed bearings off for forensic testing. The results both times: "bearing fatique". So I asked, "What is bearing fatigue". And the answer I got was that the bearings had gone metal-to-metal (balls physically contacting the races with insufficient oil molecules between the two) too hard, too often, or for too long a period of time.

    There are several factors that can cause this - some listed above.

    p.s. What year did BMW start selling and dealers and owners start installing 75W140 synthetic lubricant in final drives even though that viscosity doesn't meet BMW spec's for final drives - just for transmissions?
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
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  9. #9
    Registered User mneblett's Avatar
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    The K12LT group did something similar, and got back reports of Brinnelling of the races and spauling from excessive preload -- I agree that there are *several* potential causal agents here.

    I believe we're on the same page Paul -- I'm not one of the "oh my Dog, every BMW is a timebomb waiting to explode" camp. The number of failures in 2000-on drives was disturbingly high as a matter of industrial statistics, but far from the end of the world. I personally lived through two failures far from home, but I still did not believe it to be a "BMW's are inherently unreliable" issue.

    The *only* real discomfort I had across the last decade was BMWNA's and BMWAG's stunning silence on the issue -- they blew an *enormous* good will opportunity, and in the process made even me, a die-hard supporter, hesitate when asked "how good are BMW's?"

    BTW, when I say lost a terrific good will opportunity, I don't mean spending totally unreasonable amounts of money replacing the 96-98% of the non-failing drives -- I mean that if they had responded to the literally hundreds (thousands?) of cries for answers to the "why are they failing?" question -- even if it was just to say "we don't know, but we're working on it," then provided periodic updates and spent a relatively small amount to extend the warranty in a very public way to, say 100k miles, coupled with a "we know it's only x% of the drives, a service program doesn't make sense, but we will take care of you if there is a problem," maybe coupled with a stockpile of ready overnight VOR FDs to take care of actually down bikes, their reputation would be sterling today. But by simply not responding to the *massive* unease/fear of the unknown in the customer body, they absolutely blew an opportunity.

    If the response was along this line, instead of the absolute stone-wall we received (and are still receiving), BMW could have some of the most loyal fans/buyers/word-of-mouth promoters in the market (i.e., "hey, I love these guys because I have confidence that they will take care of me when such an important part of their product fails in a way it shouldn't, even if I'm past 3/36"). I'm well aware that BMWNA is actually one of the *best* in the industry for quietly doing "customer good will" coverage items, but the silence was deafening -- so much so that their good "they do the right thing" reputation was completely forgotten in the face of so much unnecessarily discomfort/uncertainty. There are so many former BMW owners over this issue, and so much non-BMW owner belief that the FD issue is actually a real problem, that I can't help but believe that BMW's conquest sales efforts are taking a serious hit in the U.S. (the singlar exception of the S1000RR not being a proof to the contrary).

    The ironic part is that it likely would not have been *that* much money, assuming the supplier contracts are written like most of the auto suppler contracts, where warranty repair costs are typically passed through to the supplier in the case of supplier-caused failures.

    As a BMW fan, I have to say I was ashamed of their response on this one.
    Last edited by mneblett; 11-02-2010 at 05:14 PM.
    Mark Neblett
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    I have to agree 100% with Mark

    I can't tell you how many times while on the road i have had people come up to me and say, "what a beautiful bike; but don't BMW's have a problem with the rear-end?".

    As an Accountant (don't flame me, it puts food on the table ); i understand how difficult a pill that would have been to swallow. But as a BMW owner, and long time rider, it sure would have been an incredibly smart marketing play on their part!
    Somers, NY

    Just enjoying the ride.......

  11. #11
    Enjoy The Ride saddleman's Avatar
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    Of the several final drives that I have rebuilt on the LT's the only ones with any bearing wear had to much pre-load from the factory. My personal FD that I rebuilt at 80,000 miles had no wear at all on the crown bearing. The pre-load was on the high side but within spec. I cut it apart & inspected each ball bearing plus the inner & outer race under a microscope. Not one mark on anything.
    Dave
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    Registered User mneblett's Avatar
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    Quote Originally Posted by saddleman View Post
    Of the several final drives that I have rebuilt on the LT's the only ones with any bearing wear had to much pre-load from the factory. My personal FD that I rebuilt at 80,000 miles had no wear at all on the crown bearing. The pre-load was on the high side but within spec. I cut it apart & inspected each ball bearing plus the inner & outer race under a microscope. Not one mark on anything.
    What was the failure mode of this FD?
    Mark Neblett
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  13. #13
    Enjoy The Ride saddleman's Avatar
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    Quote Originally Posted by mneblett View Post
    What was the failure mode of this FD?
    I'm not sure what your asking. All the FDs I've rebuilt execpt for one were in good shape. Mine is the only one that had the proper preload from the factory. On one FD the owner saw one little flake when he changed his oil. The LT had 102,000 miles on it and the preload was .016. Max is .004.
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  14. #14
    Registered User f14rio's Avatar
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    what's pre load?

    ntxt
    "Enemy fighters at 2 o'clock!...Roger, What should i do until then?"

    2010 r1200r, 2009 harley crossbones, 2008 triumph/sidecar, 1970 norton commando 750

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    Cam Killer marchyman's Avatar
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    Bearings apart from being mounted on the shafts and housings have to be preloaded properly for their proper functioning. Preloading is the methodology by which we remove the internal clearance in the bearing by applying a permanent thrust load to it. In other terms we can say that we push the bearing to such an extent that it has to move only in the groove (raceway) and cannot move axially in either direction. We will look on when and how to preload bearings in this article.
    From http://www.brighthub.com/engineering...les/17347.aspx

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