R1100 swingarm on R100GS, details?

Discussion in 'Airheads' started by AntonLargiader, Jan 12, 2018.

  1. AntonLargiader

    AntonLargiader Long timer

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    I'm seeing daylight on the idea that I will eventually go down this road, and want to see what is really needed. I have some very detailed pictures of the HPN shock bracket, so I know how that is done. My question at this point is really about the shock: is a standard 1100GS shock dimensionally suitable for that installation? I realize that it may be a bit stiffly sprung and valved, but those things are fixable.

    If this can be made to work with an 1100 shock then I think I may have a low enough barrier to entry that I can get serious about it. I have plenty of R1100 swingarms lying around. The R1150 one is actually nicer looking, and I think slightly shorter, but if an 1100 shock works then I have nearly everything I need.

    So, you folks that have this conversion: what can you tell me about the rear shock that you have? Are you using the HPN bracket, and how long is the shock?
    #1
  2. Jim Day

    Jim Day full manic mechanic

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    Is Jason running the stock shock configuration?

    That Rooney setup looked to have pretty close to the stock angle on the shock.

    Also do you have links to what your going to use for the top mount. I think I know that system, but from my experience very small changes in the mount positions can make big differences in performance. I would think Rooney has it down, and of course if you need anything fabbed to work with the stock configuration feel free to hit me up.

    I think you are going to love them. I really like the performance of the R1100 shock on my /6 mono conversion.The biggest thing is the reduction of frame flex, definitely more solid. it's pretty night and day when it comes to the feel.

    My next mod will probably be the R1100 swing, with a R1100GS shock with the top mount built integral into a more solid rear subframe. I know I can do one, and I'm sure I can make it work, I just have not got around to actually making one. :D

    Good luck!! I'm glad to see your doing this, maybe you can smooth over the rough edges before I get to mine :beer
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  3. Airhead Wrangler

    Airhead Wrangler Long timer

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    Care to share those? I'd be interested to see them too as I'm also heading down this road.
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  4. Jim Day

    Jim Day full manic mechanic

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    Yeah I want to see them for sure. :D

    Probably the upper mount is something similar to this:
    [​IMG]

    That bike actually uses a modified mono swingarm.
    [​IMG]
    [​IMG]

    I found those pics randomly about a decade ago before I even knew of ADV. I saved them, but then lost them on an old drive. I just found them again recently doing some archive cleanup. I know nothing about them other then the page they were on was written in German, it was someones personal page, he was some kind of backyard builder and I could not find it later.

    Even though I had not seen them for years that build was part of the inspiration for my twin arm mono mods using the R1100 and R1200 shocks. Once I realize that the lower mount can rotate around the swing arm pivot, I moved it up and forward which allowed me to moved the upper shock mount forward to the frame. Of course mine had two arms other rather then just one :D

    Most of the R1100 swingarm mods I have seen that use the original shock size have the shock almost straight up and down and use something like this.
    [​IMG]
    It's like an old A frame suspension. A simple design, not hard to fabricate at all, and it's chief advantage is it does not flex the frame like with the single shock mounted at an angle to one side.
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  5. AntonLargiader

    AntonLargiader Long timer

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    Pete, the pics I was thinking of were online and that account isn't around any more. I'm looking into it but it was basically the same as what Jim posted. That looks like the same HPN setup.
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  6. hippie nl

    hippie nl Been here awhile

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  7. Airhead Wrangler

    Airhead Wrangler Long timer

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    Anton, for shock length HPN lists a rear wheel travel of 245mm with the R1100GS swingarm while the R1100GS has a travel of 200mm from the factory, so HPN uses a shock with a longer stroke at least, not sure if the eye to eye length is any longer though.

    As for the shock mounts, Jim's photo above is close to what HPN does, but HPN has a tube with threaded inserts welded into the ends bridging between the two lower mounts on the frame, rather than nuts. Also, HPN said they use a much tougher tube for these shock mounts (chromoly, I believe) compared with the rest of their frame work. I always thought this shock setup would benefit hugely from a modern WP PDS shock designed for linkless KTMs.

    Also, not to be forgotten, they use different thickness engine mounting spacers to slide everything to the right to minimize wheel offset.

    (This first photo isn't actually an HPN frame, but a pretty accurate copy)
    [​IMG]

    The rest of these are an HPN bike, but unfortunately don't show it as clearly.

    [​IMG]

    [​IMG]


    And a really big image showing how all three mounts are welded to the frame:

    [​IMG]
    #7
  8. Prutser

    Prutser Long timer

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    Some random pictures.

    IMG_0012.jpg


    IMG_0010.jpg


    Below a 1150 swingarm was used.

    IMG_0176.jpg

    This is one I put together some time ago.

    IMG_8424.jpg

    I really like the pictures Jim posted with the extended mono. Although i.m.h.o. they could have positioned the shock a bit further from the swingarms pivot point so they would have had an easier wheel /shock ratio to work with.
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  9. Screaming Chicken

    Screaming Chicken Long timer

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    And the alternative way:

    [​IMG]
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  10. Jim Day

    Jim Day full manic mechanic

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    He's playing the same game I did with my R75/6.

    Anton already said it in his opening post. The stock shocks are a bit stiffly sprung and valved for our bikes. That said you can not only use those stock shocks unaltered but actually get more travel out of them simply by reducing the distance from the swingarms pivot point to the shocks lower mount. It's definitely hard to dial that in because small adjustments make for large changes, but I was able to do it and it's not brain surgery.

    On the /6 I'm running the unaltered stock shock from the R1100RT which only gives 135mm of travel with the R1100 para swingarm but I'm probably getting closer to 185mm of travel out of it (maybe a little more) due to the shocks angle and that shortened distance between the swingarm pivot and lower shock mount. Thats with a relatively short /6 modified twin swingarm with a 65mm extension. It looks like he's running a longer (probably R1100GS) shock, and if he's worked it out right that will give him significant travel with his shorter pivot to lower shock mount distance.

    That would explain the height of his fender mount.
    [​IMG]

    Another thing I see that we did similar was the angle. His shock leans forward enough that there is a significant angle at the lower shock mount point in relation swingarms pivot point at full extension, but as the shock loads up that angle is reduced to 90 degrees at compression. Think rear brake lever. The effective spring rate decreases as the mounted angle increases. Under full load the shock is essentially stiffer working exactly as designed, but it lightens up as the arm is extended. Just another trick to get more out of the shock. I tried that geometry on the R75, and I think there are some advantages to it.

    I do love the look of his red mono, it's just so clean.
    [​IMG]
    Anyone know who's bike that is?

    It's interesting to me because back when I saved those pics I thought those mods would be way too difficult to try, and now they seem relatively straight forward or even easy to me. :D
    #10
  11. Heipaal

    Heipaal Always the hard way

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    A bit offtopic but anyone knows what underseat storage tray is used here?
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  12. Airhead Wrangler

    Airhead Wrangler Long timer

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    HPN makes it:

    51.205.10 Tool compartment HPN-Sport 125,00 €
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  13. AntonLargiader

    AntonLargiader Long timer

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    #13