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Lowering air sprung fork

Discussion in 'Downhill & Freeride' started by Verskis, Jan 29, 2013.

  1. Verskis Member

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    I've not ever owned an air sprung fork, so I don't have any hands-on experience on them.
    I know you can easily lower them (decrease suspension travel) by sticking a spacer on the negative spring side.
    But how do the negative air spring work then? As I have understood, all but RS Dual Air forks have auto adjusting negative springs, so there must be a channel open between the main spring side and the negative spring side when the fork is fully extended to equalize the pressures on both sides. But this channel must close when the fork is compressed, right? So when the fork is lowered, how does this pressure equalizing channel work? Or am I way off with my explanations?
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  2. Mr Nug Member

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    I'm not sure about spacing out the negative spring comment but in my Argyle (which only has a positive spring) to reduce the travel a spacer is inserted inside the spring leg in such a way that less of the rod protrudes from the uppers, effectively reducing the available travel.
    Last edited: Jan 29, 2013
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  3. kidwoo Celebrating No-Pants Day

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    it's not a channel

    The eq system is on the piston, not on the stanchion wall like an air rear shock.
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  4. climbingbubba New Member

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    This is true. I remember hearing people having issues with Totems and the air channel being blocked by the spacers if you used one that wouldn't allow air to go through (around, in, past, whatever) the spacer. So in some instances, with the wrong spacer, you could potentially have a problem with the fork equalizing
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  5. kidwoo Celebrating No-Pants Day

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    The ones I've lowered were a little schrader valve thing on top of the piston. The negative chamber would get a little squirt the first time it topped out and it would equalize.

    I'm trying to remember what the fox forks look like. I've lowered a bunch of 36s down to like 2.5 inches of travel and never had a problem with them equalizing. But it's not the same system as the RS air forks. I think it's just a physical top out spring with no negative chamber.

    The good thing to know is that fox spacers to fit on the RS forks I've shortened.
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  6. Verskis Member

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    Thanks for the help guys.
    So in RS forks there is a valve in the piston, X-Fusion forks seem to have a coil spring on the negative side so no need to equalize pressures (http://www.xfusionshox.com/images/pdf/2011-Vengeance-Travel-Adjust.pdf), and Fox forks may have a similar system as X-Fusion?

    I'm most interested in lowering X-Fusion or Rock Shox forks, as I've been thinking about getting a X-Fusion Vengeance or RS Lyrik and lowering it to 140mm. Seems like with the Vengeance I would need to change the pin position and have a 10mm spacer, and in Lyrik I would need 30mm of spacers.


    By the way, there is definitely a gap in the product portfolio of all the major suspension manufacturers, I would think there are numerous people that want to have a stout fork chassis with quality damping (meaning proper shim-based system with proper fine-tuneable adjustments (at least for LSC and LSR), not any of that RS Motion Control plastic tube crap, or Fox CTD or X-Fusion RL2 "adjustments"), but not 160-170mm of travel.
    Luckily you can buy a good 170mm fork and lower it to have a decent product for hard-hitting trail bikes.
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