Upper stanchion crimping failure

Discussion in 'GS Boxers' started by chef_of_the_future, Nov 4, 2016.

  1. TUCKERS

    TUCKERS the famous james

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    So it's a construction cost issue no doubt. They changed it to save money. Hnads up who wants to ride a bike with crimped and glued fork legs......hands up.
    JIM, are you getting the Britome fix for your bike or making something or disregarding the weak point?
  2. 65SlashTwo

    65SlashTwo Da Pigu

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    I'm anxious to see the fix & talk with the dealer. Personally I'm probably going to ride it and keep a close eye and feeler gauge handy as I'd
    really like to avoid having to mount the stanch clamps. Reason being is that I can see a real pinch potential with my control cables and brake lines
    coming from the bars. I installed ROX pivoting risers and did the cable relocation thing to outside the stanchions. Seeing other SC installs that contact
    bodywork at extreme angles concerns me as keeping up on offroad skills means occasionally doing lock-to-lock figure-8 drills that will pinch
    in these areas.
  3. TUCKERS

    TUCKERS the famous james

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    Are you going to take it up to 120mph? Are you going to stop every 10 miles and check the fit? Are you going to ride a tank of gas (two hours) on uneven terrain and not stop for a look? It's just a $25,000 motorcycle, perhaps you shouldn't expect any different?
  4. JimVonBaden

    JimVonBaden "Cool" Aid!

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    It may or may not be a construction cost issue. We do not know that. The engineers may have determined that thinner fork tubes were fine, nut not fully accounted for the issues created by not being able to thread them, and instead press fitting them. We will likely never know where the mistake was made in the engineering of them. Some indication will likely reveal itself when BMW either redesigns them, or comes up with a fix for the existing ones.
  5. TUCKERS

    TUCKERS the famous james

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    At least we agree that it is a mistake by BMW. What will you do Jim? I value your input.
    Be real though...why go crimp? Becuase it's better or to save money?
  6. Bill-66

    Bill-66 Hencho in Kansas

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    If it has telelever, the arc is there...it's just dealt with in a different way...

    2 minutes with a compass and you could see this plainly..or, look at the animation above..which is spot on and not dependent on the "length" of the fork...
  7. JimVonBaden

    JimVonBaden "Cool" Aid!

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    I'm not sure what the alternative is. Maybe the upper fork tubes will need to be replaced with thicker ones that can be threaded. :dunno

    I'm doing nothing. I am a street rider who does light gravel occasionally. I'm at low risk, but will roll down the rubbers now and then for a check.

    [​IMG]
  8. TUCKERS

    TUCKERS the famous james

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    It's FAR from spot on. The animation should show what really happens. Top 8" of fork leg sliding down the next 10" of fixed leg above the bottom triple. Back to the computer animation program and do it right...that's all. No need to insinuate that 2 minutes and anyone could see this, with a compass. That's not fact. I have a view you have a view. I'm not saying anyone with a compass can prove this.....I'm saying it's a shit design and I don't believe it arcs. Whomever did the animation needs to go back and do it on a program that shows what happens when all the components are connected as per percentages of construction on bike.
    What's going to happen next is someone is going to say "tuckers never quits, tuckers will argue"...yet many people come on and discuss and argue. This is my pre-ban disclaimer, I'm going to agree to disagree.
    What do you want me to say? "Anyone with half a brain can see it's shit?" That's not nice.
    Let's discuss it ad nauseum and then agree it's shit.
  9. TUCKERS

    TUCKERS the famous james

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    How often will you check Jim? Everytime you get off your bike? Everytime you get where you are going? Everytime you get home? Everytime you get gas? Service intervals? When will you decide it's seperating? At what measurement?
    I value your input as you work on these bikes constantly and even do videos about them, you obviuosly know your stuff as a mechanic.
  10. JimVonBaden

    JimVonBaden "Cool" Aid!

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    I checked a few months ago Maybe I will check at the next service in a few months, or when I think about it. I'm not particularly worried about it. There are still very few with an issue, and those with an issue have either had a high impact incident, or have done significant off road from what I can tell.

    It is pretty clear ANY movement is cause for concern. .002 gap is, IIRC, the spec for proof of movement.
  11. Brokein2

    Brokein2 Been here awhile

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    The "Buckling" was to illustrate my invisible accordion fork boots... :clap

    I didn't draw the illustration nor do I want to argue about it's effectiveness as a design. Obviously BMW did it for a reason, but now that real world use has started to point out the fact that it is in reality probably not adequate, they need to come up with a fix. The illustration when shown full size probably didn't have any of that buckling showing, but as soon as you scale down an illustration on a computer screen - the pixels move sort of chunky and cause certain things to not appear as they originally did.

    The clamps that Britome is selling came from my original design that he improved upon and took the time and effort to get produced and should reduce the movement that over time separates the bond between the fork cap and stanchion. As a 25+ year ME at Boeing, I have seen some poor designs in my day due to cost structure. Think 787 battery and then the subsequent explosion proof 3 layer vented box :doh required to keep them flying.

    This is one place BMW should have designed in a hell of a lot more redundancy.
  12. Jaws

    Jaws Awesome Adventurer

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    They have to pivot in the triple tree because the cantilever arm is actually a pivot arm rotating from its pivot point (red crosshatch).

    I added the red circle to the diagram to help illustrate this point. As the suspension compresses and it gets closer to the triple clamp the angle between the end of the arm and triple clamp changes, as well as the distance. The sliders make up for the change in distance, but they have to pivot in the triple to make up for the change in angle.

    Cantilever.jpg
    bemiiten and Brokein2 like this.
  13. TUCKERS

    TUCKERS the famous james

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    What about the shock absorber midway between your red X and the lower triple?
  14. TUCKERS

    TUCKERS the famous james

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    Perhaps the design construction is patent related. I just don't see the arc. I'd like to see a quality computer animation of the whole structure.
  15. Yossarian™

    Yossarian™ Deputy Cultural Attaché

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    Here's a static view. I hope it helps. The "bottom triple" is where the telelever arm attaches; you can plainly see that as the fork tubes telescope in and out, that there is an arc defined by the movement of the telelever arm.

    [​IMG]
    JimVonBaden and Pch123 like this.
  16. TUCKERS

    TUCKERS the famous james

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    No I don't plainly see that arc. Actually this illustrates how unlikely it would be to arc
  17. TUCKERS

    TUCKERS the famous james

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    Shock of course goes straight up and down, taking the top triple with it
  18. Yossarian™

    Yossarian™ Deputy Cultural Attaché

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    I'm sorry, I can't help to explain how incorrect your assumption is.
  19. JimVonBaden

    JimVonBaden "Cool" Aid!

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    James, you do not see it because you do not want to see it. There is no way this does not have an arc, or maybe it is the term "arc" that has you stumped. :dunno
  20. JimVonBaden

    JimVonBaden "Cool" Aid!

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    Actually, the shock goes up at an angle, and pivots slightly. That is why it has a straight rod on top mounted in rubber. Kinda like the way the top of the fork tubes are mounted.
    FlyingFinn and 65SlashTwo like this.