Broken R100GS subframe

Discussion in 'Airheads' started by scottw, May 31, 2004.

  1. scottw

    scottw Steppe Rider

    Joined:
    Sep 15, 2002
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    Well, took off the seat today to get at the toolkit and found a clean snap in the right rear subframe. Must have happened last weekend when I went offroading for about 50 hard miles. Will have to get it to a welding shop later this week.

    As long as I'm taking it to a welder, any suggestions for how to fix and strengthen it for the future? I'm going to have them beef up the left side as well while they're at it. I guess these things happen when you're trying to make it act like a 500 pound dirt bike. :rofl :D :evil

    -Scott
    #1
  2. mitch

    mitch Long timer

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    I think BMW has a mod out for problem, I seem to remember it was for Aust and Canada.

    Good Luck.
    #2
  3. Rubber Cow

    Rubber Cow GS Dork

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    There is a freame gussetting kit available from HPN/Wudo and I think Touratech as well. It is only intended to reenforce the main frame. Unfortunatly, this has the effect of stiffening the frame too much and causing it to crack in other places....like in the middle of the top tube. Not good.
    The best thing to do with the subframe is to have an identical one made up out of better, higher grade chromoly tubing. High end bicycle tubing would work in a pinch.
    Jim Rowley of MAP Engineering or HPN may be able to sell you or at least suggest some alternative/stronger designs.
    My suggestion would be to remove the subframe, cut it in the identical spot on the left side, insert a tube/hollow pin between the broken bits, braze it in place or at least cross pin it, and then weld the subframe back together.

    What were you doing and how much load was on the seat and rack?

    Hope this helps.
    Cheers,
    Jorge
    #3
  4. scottw

    scottw Steppe Rider

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    Thanks for the suggestions Jorge. I don't know exactly when it happened, but there was no extra weight on the rack or rear part of the seat. Of course, I weigh 260 (probably 280 in full ATGATT) so that's not insubstantial. But my weight is usually more forward.

    I'll try MAP Engineering and HPN. I have the HPN tank on the bike. Good stuff, but expensive.

    About 90% of my riding is off-road, on dirt tracks or cross-country. It's not like I'm doing jumps or anything, but many hours of very bad dirt roads or bumpy pasture land at 25-50 MPH, so a lot of rattling and hits.

    -Scott
    #4
  5. Frank Warner

    Frank Warner Traveller

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    HPN reinforce that part of the frame buy adding another frame tube - to form a larger tiangled section towards the rear of the bike,

    Runs from the rear part of the rear rack towards the bottom frame attachment point - near the swing arm pivot point.

    This will not cause other parts of the frame to brake earlier than they other wise would.

    --- From the photo - the frame gusset has been broken for some time - rusty. The frame tube is recent - no rust. Perhaps others can use this as a test for frame failure?
    #5
  6. dehager

    dehager Been here awhile

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    Subframe broke on my 95 RS two weeks ago. ~$450 for an updated subframe and ~$80 for the updated luggage assembly. I figured I would do all the maintanence now, clutch, splines, rear main seal. I had the biked stripped and trans out in two hours.

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    #6
  7. dehager

    dehager Been here awhile

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    Just a little heat and they came out like melted butter. I love MAP gas.

    Charles likes fire a bit too much. :nod

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  8. dehager

    dehager Been here awhile

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    .

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  9. Possu

    Possu de-nOObed!

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  10. Cpt. Ron

    Cpt. Ron Advrider #128

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    Frank is right, that was a problem in the making quite a while ago. I had a similar crack with another gusset further back on the submframe. I caught it before it could stress the tubing and crack it.

    Mitch, the pieces you speak of are for the R1100GS's where the subframe mounts to the transmission. This doesn't apply to the airheads, but I highly recommend it for the affected bikes.

    Rubber Cow's suggested fix is the best one, if you have the guts to cut up your subframe.
    #10
  11. Stephen

    Stephen Long timer

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    Airhead subframes have been breaking since the '70s. The solutions are pretty obvious: brace'em, with a diagonal or a trellis. That way, you could move the failure point forward to the attachments.:lol3 Or carry less weight back there.
    #11