800GS shock bolt design flaw?

Discussion in 'Parallel Universe' started by johngil, Jul 16, 2009.

  1. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    Does the rest of the bushing serve any purpose? From the flats left it looks like it's just hanging there.

    In this photo you've got a hose on it?

    [​IMG]
    #21
  2. johngil

    johngil Reseda, CA

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    The trouble started w/ the stock shock.
    #22
  3. johngil

    johngil Reseda, CA

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    The "hose" is from BMW.
    The whole setup is meant to mount the seat lock mechanism. Notice the opposite side. They could have lost a couple of inches of fastener if they simply just mounted the shock.
    #23
  4. johngil

    johngil Reseda, CA

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    Ohlins. It will be getting measured compared to stock tomorrow.
    #24
  5. johngil

    johngil Reseda, CA

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    This is the problem w/ the design in my opinion. The span is just too large.
    [​IMG]
    #25
  6. tmex

    tmex Long timer

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    John, it "appears" to me that the upper mounting flange on the Ohlins is much smaller than the flange on the stock shock. The shorter flange would certainly aggravate if not actually induce the problem since it would be much easier to bend the mounting bolt with a smaller flange. The force would be much more concentrated with the Ohlins.

    As it stands, the frame looks severely bent at this point and will probably need to be replaced even if you go back to the stock shock. After looking at your photos I would be reluctant to use the Ohlins as designed, although I am not sure I would have been smart enough to come to that conclusion apriori. I might be inclined to pick a fight with Ohlins if I were you (assuming they designed that shock for the F8). I'll take a look at my F8 this weekend since it is not at my current location.
    #26
  7. johngil

    johngil Reseda, CA

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    Dennis, when comparing the stock shock to the Ohlins there is more surface area w/ the Ohlins shock. The stock shock looks larger, but is mostly just a rubber bushing w/ a smaller steel sleeve.
    I will have both shocks compressed to make sure they are of equal length today.
    The bolt bending started while running the stock shock. The Ohlins was to be a fix for the frequent bottoming.

    After the shocks are compared and everything checks out, I'll start by calling BMW and go from there. I was told that the local rep. is out for injuries right now. That isn't going to help me.
    #27
  8. v8toilet

    v8toilet Nothing to see here.

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    Unless he.she was injured when his rear shock bolt on his F800 let go.... Keep us posted. :deal
    #28
  9. TwilightZone

    TwilightZone Long timer

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    Wonder if replacing the stocker with a high strength titanium bolt would do the trick. Gotta be available out there somewhere on the internets.
    #29
  10. Kawidad

    Kawidad Long timer

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    Ti is cool and all, but it is really brittle. I don't think I would want that, bending is better than snapping for this application.






    I have to agree this looks like a silly design. But, if you are frequently bottoming out your shock like you said, that may have been the original source of the problem.:deal
    #30
  11. itsatdm

    itsatdm Long timer

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    I felt concerned enough about this to pull my shock bolt and luckily it is OK. The measurement I got between the mounting flanges was 2 3/4 in. The stock shock spacer is 1 3/8in and whole set up seemed to be a poor design. Then I pulled the rubber seat latch and noticed it too had a spacer. When the bolt is tighted to spec the two spacers butt up to one another and should provide a good reinforcement to the bolt. So not as bad as I thought.
    I can see that if an aftermarket shock did not have a spacer as wide as the stock one, there would be no reinforcement for the bolt and it could bend which in turn could bend the crossmember.
    For the stocker to do that, it looks like it had to be under a lot of pressure, had an improper spacer installed or a frame not to spec in width.
    #31
  12. johngil

    johngil Reseda, CA

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    The Ohlins re-uses the stock spacer.
    #32
  13. johngil

    johngil Reseda, CA

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    I did just that.
    BMW wants the bike back to the shop for further evaluation. A rep. from BMW NA will be sent to the shop, hopefully next week.

    The folks @ BMW NA are very responsive. I'm crossing my fingers.
    #33
  14. DockingPilot

    DockingPilot Hooked Up and Hard Over

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    Keep us in the loop John. Good luck.
    #34
  15. johngil

    johngil Reseda, CA

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    My BMWNA rep. now works for BMW Canada.
    I hope I can easily find out who is looking after things now.
    The bike has been returned to the dealer for a closer inspection.
    #35
  16. 88NX250

    88NX250 Team USA

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    Not sure if that has already been suggested but check your rear shocks for signs of coil bind. If you have your pre-load set so high that the SPRING is locking on itself before the shock bottoms out you are risking significant damage (like what you are experiencing).

    If your bike was doing this with the OEM shock than it probably isn't the problem unless you modified the OEM shock/spring before the problem started.
    #36
  17. johngil

    johngil Reseda, CA

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    Well, it took some poking around but I am starting to find others that are bending their bolts.
    This could get interesting.
    #37
  18. tmex

    tmex Long timer

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    Interesting... Please keep us appraised. I do not think it is a great design, but it would not have set off any alarm bells either. Maybe there is a tolerance buildup issue with the shock bolt mounting tab spacing (frame size) and the spacer size that needs more careful attention at the point of assembly. I think I have pounded mine pretty hard, and did not see any evidence of bending but did not actually remove the bolt. BTW, I have my preload set at pretty much the max (can't turn the knob anymore by hand, and I am not limp wristed).
    #38
  19. johngil

    johngil Reseda, CA

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    I understand. No, really I do.:toney:evil

    It wouldn't hurt to loosen the bolt and re-torque. The way the rubber forms around the bent bolt in the top eye of the shock may hide a lot.
    #39
  20. johngil

    johngil Reseda, CA

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    I have been taking motorcycles apart and putting them back together as long as I have been riding them. 32 years. This design is a new one on me.
    I do not have any formal engineering background and don't claim that the numbers don't work in the case of the shock bolt and mount area on the 800. But my frame is bending.
    I can say in my opinion, the bolt is spanning too great an area and is begging to bend when stressed more so than the conventional mounting methods used by other manufacturers. The bolt diameter is also pretty small compared to what I have seen as well.
    I'm not over-confident that I will get BMW to repair my bike. I can only hope.

    My riding style may be faster or more aggressive than the intended user for this machine, but that's not saying much. I haven't launched this bike or hammered sets of stadium whoops w/ it. I have never even crashed (in motion) this bike. I can ride all day long and come back for more tomorrow. That said, I ride so that I can ride again another day. I would expect this bike to hold up to frequent off road use.
    I'm finding lots of folks who have bought and sold 800's after coming to some realizations re: it's longevity when used off road.
    I truly enjoy this bike and will be sad when she goes.

    Joel, can you look at this mounting design and honestly say you feel it is a good one?
    Again, it begs to fail in my opinion.
    I will wait for BMW's response and go from there.
    #40