Need advice on headshox...

Discussion in 'Mountain Bikes' started by Hipsterdoofuss, Apr 17, 2003.

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  1. Hello,

    My old cannodales headshox mc50 is completely seized. I don't have alot of bike repair under my belt
    but I am fairly handy with tools. Can anybody educate as to the difficulty level of his project? or
    should I send the buisness to the bike shop.


  2. David Kunz

    David Kunz Guest

    Hipsterdoofuss wrote:
    > Hello,
    > My old cannodales headshox mc50 is completely seized. I don't have alot of bike repair under my
    > belt but I am fairly handy with tools. Can anybody educate as to the difficulty level of his
    > project? or should I send the buisness to the bike shop.

    If it's completely siezed you may be able to get it apart. You'll need new races and bearings from
    the bike shop anyway -- you'll need to measure the thickness of the old races to 0.001" to tell them
    what you need and you'll need to make sure that you get the news ones back where the old ones of
    that thickness came out or the fork will bind. BUT, unless the bike shop has a wrench that's done a
    head shock before, its likely to get trashed. Your decision. Here're my notes on the Lefty. A newer
    head shok should be similar, I don't know about older ones.

    Do you have access to the castle tool to remove the shock cartridge? If not, then instructions won't
    do any good. You may be able to borrow it from your LBS -- mine loaned theirs to me -- they don't
    need it often :).

    But... I've done a lefty several times, and the head shok is similar -- I only had instructions for
    the head shok and had to figure out the lefty the first time.

    You'll need to make a "tool" to hold the outer races in place. This nothing more than a road tube
    with the ends knotted (actually, I used zip ties to seal it). You want it to be long enough to go
    from the top of the fork to close to the bottom of the top tube. Cut a couple of stips off the inner
    tub before sealing it -- you'll need them to hold the bearing strips in place.

    Headshok: Remove the stem (you can probably get away with just loosening
    it). Remove the Lockout -- just pulls out (headshock: held in with a screw). Remove the plate under
    the lockout -- you'll need a pin spanner. Remove the air from the shock. Push down on the fork to
    get the top of the cartridge out far enough to get the castle tool under it and engage the
    cartridge. Remove the cartridge -- cannondale special castle tool. Remove the the air chamber --
    push it up using a piece of vacuum tubing. With a lefty, remove the shock: remove the brake
    caliper and front wheel; loosen the 3 bolts clamping the fork to the frame; pull down, working
    the rubber ring up as you pull the fork out. Headshok: remove the front wheel. Remove the tie
    wrap from the top of the boot and push the boot down. I held mine down with a small wood clamp.
    With a headshok, you may need to remove both tie wraps and push the boot totally out of the way.
    Remove the ratainer at bottom of the top fork tube (under the top of the boot when the boot's in
    place) -- pin spanner. (may not be there on a headshok) You can now see the bottoms of the outer
    races sticking out. There's probably a retaining ring holding them in place (clip that has
    notches in it that the races spring up into). Remove it. You'll probably also find a retaining
    ring (clip that fits into notches in the races) at the top of the inner races -- you get to this
    from the top of the fork tub. Remove it. I use a long screw driver to push the races out (one at
    a time) and a spoke bent to be a hook to pull up on the ring. Clean the grease off the inner
    races and use finger nail polish to mark their position in case they fall out -- I number them.
    Put electical tape around the bottom of them to hold them in place. Also mark the outer races so
    that if they fall out, you can get them back in the right place. Since only a little sitcks out,
    different colors is helpful here. The races are different sizes (in pairs) to 1/1000th of an inch
    and getting them back in the right place is very important. If you don't, the fork will bind. On
    the lefty, all of my outer races were the same; I'm told that all of the inner races are the same
    on a head shok. Slowly pull down on the telescope until about 5-8 bearings are showing. With a
    lefty, slide a ring cut from the inner tube over the top of the fork and down over the bearings
    to hold the bearings in place. For a head shok, I'd hold the bearings with my hand as I slide it
    apart so that I can see where to put them for reassembly (how many bearings above/below the top
    of the fork at the engagement point. Put the "tool" that you made into the top of the fork; put a
    little air in it and push it down until it's against the top of the telescope. Pump it up. It's
    going to hold the outer races in place when you get the fork apart. Continue to pull down and the
    fork will come apart. Note the height of the inner races above the top of the telescope. Make
    sure that you get them back to that height during reassembly. Same thing for the bottoms of the
    outer races WRT the bottom of the outer fork tube, and the height of the bearings WRT to top of
    the fork. Clean and grease everything well using a high quality, light weight synthetic grease. I
    use Phil Waterproof Grease. Do one race at a time.

    To reassemble... The inner and outer races should be in place. The inner race should be taped at the
    bottom. Refresh the tape if you need to. Use the inner tube strips like rubber bands to hold the
    bearing strips on the inner races. Overhang the inner races by 11 bearings (should be the center of
    the strip). Carefully engage the two pieces. The bearings and the outer races will want to slip and
    move. Once there're even slightly engaged, the tolerances are so tight they can't be shifted. If you
    need to start again, do so! It can be tedious. Get it right. As things go together, slide the inner
    tube rubber bands down and cut them off or slide them off the top (lefty) when you've got the fork
    together to your satisfaction. Put the clips back and put the clip retainer back. Use lock-tite on
    the clip retainer. Put the top clip back in. I use the same very long screw driver and bent spoke --
    this can be a tedious step. Regrease the exposed inner races and put the boot back. I hold off on
    the tie-wrap until I'm done. With a lefty, the fork'll be covered with grease from your hands -- I
    clean it at this point :). Put the lefty fork back onto the bike and put the wheel back on (you can
    put the brake on now or later). Put the air cartridge back in. You might want to put a little fork
    lube in it and dump the excess out. I use motorcycle fork lube. Make sure that it doesn't have any
    seal swelling chemicals in it! I lower it and the shock cartridge back down with the vacuum tubing.
    Use locktite on the shock cartridge (lefty). It should be about 125 in-lbs. Put the top plate,
    lockout, stem, etc. back on. Pump it up and test it!
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