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  1. #1
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    Visibile length of a shock's shaft

    I've got a 200x51 Fox RP23 (2008). It has been serviced and I'm confused by the result - now the visible length of the shaft is more like 57-58 mm. The eye2eye looks the same - 200 mm.

    Is there a possibillity of an incorrect assembly that could lead to such effect?

    Should the visible part of the shaft be equal to the stroke, which is 51 mm? I assume you couldn't measure the sag correctly if the shaft was longer than the its actual stroke?

  2. #2
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    Quote Originally Posted by lpdot View Post
    I've got a 200x51 Fox RP23 (2008). It has been serviced and I'm confused by the result - now the visible length of the shaft is more like 57-58 mm. The eye2eye looks the same - 200 mm.

    Is there a possibillity of an incorrect assembly that could lead to such effect?

    Should the visible part of the shaft be equal to the stroke, which is 51 mm? I assume you couldn't measure the sag correctly if the shaft was longer than the its actual stroke?
    Most rear shocks the exposed stanchion is longer then the actual stroke. You let all of the air out of the shock and compress the frame. After doing so you measure how far the shock moved, this is your travel. Then you set SAG in accordance with that measurement.

  3. #3
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    It is normal. If I remember correctly 200 x 57 and 200 x 51 shocks are nearly identical (only damper body cap thickness and IFP-depth is different). When that shock bottoms out you have some "unused" stanchion/shaft tube.

  4. #4
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    I cannot remeber that exactly, but it seems that previously the unused stanchion length had been about 2-3 mm at most which is normal for an air shock as it ramps up toward the end and cannot be compressed fully except for very hard hit situations. Now it's gonna be some 6-7 mm?

    As well, doesn't the extra stanchion length affect the BB height?

  5. #5
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    At least I have a couple of Fox air Shocks (another is 200x57 and another 200x51) and the only difference is what I mentioned before. Unless you have 200 x 57 shock it should have about 6-7 mm of exposed stanchion/shaft at bottom out (might be hard to get the last mm's because of the o-ring bottom out bumper inside the shock). Unless things have changed since?

    It does not affect BB height at the top of the stroke because eye to eye lenght is the same. But you might have some clearance or other problems at the bottom of the stroke if your frame was designed for 200 x 51 shock and if you are using 200 x 57 shock. Otherwise more exposed stanchion/shaft length does not cause any problems.
    Last edited by tune; 03-19-2013 at 06:30 AM.

  6. #6
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    Quote Originally Posted by tune View Post
    It does not affect BB height at the top of the stroke because eye to eye lenght is the same. But you might have some clearance or other problems at the bottom of the stroke if your frame was designed for 200 x 51 shock and if you are using 200 x 57 shock. Otherwise more exposed stanchion/shaft length does not cause any problems.
    Well, logically if the eye2eye is the same 200mm, the stanchion length could not have changed.

    I'm running the shock on a 2008 Giant Reign. A lot of people have switched from the stock 200x51 to 200x57 on that frame with no apparent problems.

    It just feels weird as I have a clear memory of measuring sag from the 51 mm of the shaft being visible.

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