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  1. #1
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    Increasing travel on a '04 Stumpy

    Hiya all. I have a question about the travel on a 2004 Stumpjumper FSR. What I am wondering is if you can increase the rear travel of the bike to 120mm by simply replacing the stock linkage with the linkage from a 2005 (or later) Stumpy that was designed for 120mm. I have asked the local Specialized dealers here, but none of them seem to know. I am also aware that betd makes replacement linkages that will alter the travel, as well as head tube angle/bb height, but have heard that they increase the leverage on the shock to such an extent that it is damaging.

    Anyhow, thanks in advance and I look forward to your replies...

    ben
    A man who carries a cat by the tail learns something he can learn in no other way.

  2. #2
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    Quote Originally Posted by silent713
    Hiya all. I have a question about the travel on a 2004 Stumpjumper FSR. What I am wondering is if you can increase the rear travel of the bike to 120mm by simply replacing the stock linkage with the linkage from a 2005 (or later) Stumpy that was designed for 120mm. I have asked the local Specialized dealers here, but none of them seem to know. I am also aware that betd makes replacement linkages that will alter the travel, as well as head tube angle/bb height, but have heard that they increase the leverage on the shock to such an extent that it is damaging.

    Anyhow, thanks in advance and I look forward to your replies...

    ben
    Main difference between the various models seems to be the shock's length, but the ratio offered by the link is quite similar:
    2004 uses a 165.1mm shock, 38.1mm travel, ratio=100/38.1=2.62x
    2005 uses a 190.5mm shock, 44.5mm travel, ratio=120/44.5=2.69x
    2006 uses a 196.9mm shock, 50.8mm travel, ratio=130/50.8=2.56x

    So if I where to put a 2005 link on a 2004, I guess I would end up with 2.69*38.1=102mm travel! The link looks probably the same, maybe slightly correcting the geometry for the longer shock.

    The BETD link increases the leverage, but this shouldn't be a problem unless you're a heavyweight fellow and need to increase the pressure way more than 250psi (absolute max 300psi)

    In my case I run around 180psi in the shock (for 75kg), going to a BETD link I would probably have to increase the pressure to something like 130/100*180=234psi which is indeed already quite high.
    Last edited by djska; 03-17-2006 at 05:55 AM.

  3. #3
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    Quote Originally Posted by djska
    Main difference between the various models seems to be the shock's length, but the ratio offered by the link is quite similar:
    2004 uses a 165.1mm shock, 38.1mm travel, ratio=100/38.1=2.62x
    2005 uses a 190.5mm shock, 44.5mm travel, ratio=120/44.5=2.69x
    2006 uses a 196.9mm shock, 50.8mm travel, ratio=130/50.8=2.56x

    So if I where to put a 2005 link on a 2004, I guess I would end up with 2.69*38.1=102mm travel! The link looks probably the same, maybe slightly correcting the geometry for the longer shock.

    The BETD link increases the leverage, but this shouldn't be a problem unless you're a heavyweight fellow and need to increase the pressure way more than 250psi (absolute max 300psi)

    In my case I run around 180psi in the shock (for 75kg), going to a BETD link I would probably have to increase the pressure to something like 130/100*180=234psi which is indeed already quite high.
    So it sounds like you're saying you'd only get another 2mm out of the shock??? That was a lot of technical jargin so I may be completely misunderstanding.
    There's a fine line between courage and foolishness. Too bad it's not a fence.

  4. #4
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    Quote Originally Posted by djska
    Main difference between the various models seems to be the shock's length, but the ratio offered by the link is quite similar:
    2004 uses a 165.1mm shock, 38.1mm travel, ratio=100/38.1=2.62x
    2005 uses a 190.5mm shock, 44.5mm travel, ratio=120/44.5=2.69x
    2006 uses a 196.9mm shock, 50.8mm travel, ratio=130/50.8=2.56x

    So if I where to put a 2005 link on a 2004, I guess I would end up with 2.69*38.1=102mm travel! The link looks probably the same, maybe slightly correcting the geometry for the longer shock.

    The BETD link increases the leverage, but this shouldn't be a problem unless you're a heavyweight fellow and need to increase the pressure way more than 250psi (absolute max 300psi)

    In my case I run around 180psi in the shock (for 75kg), going to a BETD link I would probably have to increase the pressure to something like 130/100*180=234psi which is indeed already quite high.

    So, anybody try putting a 7.75 X 2.0 shock on a 120 FSR? How about a 7.5 X 2.0?

  5. #5
    Humpmaster general
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    Quote Originally Posted by anand
    So, anybody try putting a 7.75 X 2.0 shock on a 120 FSR? How about a 7.5 X 2.0?


    What would happen if you put the 2005 120 mm shock on a 2004 100 mm bike?
    your moma's so ugly, one time she looked out of the window and got arrested for mooning

  6. #6
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    Quote Originally Posted by Jack Hass
    What would happen if you put the 2005 120 mm shock on a 2004 100 mm bike?
    You'd massively raise the BB and steepen the HA. You'd be better off getting the BETD link and have you shock Pushed for the bike with that link's increase in leverage.
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  7. #7
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    Quote Originally Posted by S-Works
    You'd massively raise the BB and steepen the HA. You'd be better off getting the BETD link and have you shock Pushed for the bike with that link's increase in leverage.
    To get the HA back to couldn't you just then add more travel at the front? Say a float fork130mm - then you wuold have a longer travel bike at both ends, and you'd have fixed the issue with the stumpy BB being a tad low, at least I've always thought it was a bit low. Am I crazy?

  8. #8
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    Quote Originally Posted by bwolmarans
    To get the HA back to couldn't you just then add more travel at the front? Say a float fork130mm - then you wuold have a longer travel bike at both ends, and you'd have fixed the issue with the stumpy BB being a tad low, at least I've always thought it was a bit low. Am I crazy?
    You're not crazy; it's a bit low. I frequently "tap" my pedals on things while riding. I'm on a loaner Flux right now and I've noticed how I generally don't have to worry about clearance issues with this bike...I have to worry about a whole host of other things I don't like but that's not one of them.
    There's a fine line between courage and foolishness. Too bad it's not a fence.

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