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  1. #1
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    Swapping out my headshok on my old Jekyll to a fox fork, what do i need?

    Hey, this is probably pretty basic but I have searched the FAQ and wasn't successful so here goes. I recently decided to change out my beloved headshok fork on my '04 Jekyll, for a Fox 140 RL with a 1.5" steerer tube. Not sure what i need to do to make the conversion. Will this fork just mount directly in the SI bearings like my headshok or do i need to change out the headset bearings with something else?

    I don't do a lot of work on my jekyll, but swapping out the fork seems like it should be pretty straightforward and i have had the headshok out to be rebuilt, but that about it, so please forgive my ignorance regarding this conversion. Any info or advice is greatly appreciated!

    Jack

  2. #2
    Just a flesh wound
    Reputation: Prophet Julio's Avatar
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    I don't really know, but I think the SI bearings are slightly different in size for a straight up swap. You could put a Lefty in there with the same bearings though! The Fox 140 RL will change the geometry, so if that doesn't bother you, get a Lefty on that thing. Maybe a 130?
    My name is Chris and I ride a Prophet 650b with a Lefty.

  3. #3
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    Well, the bottom of the steerer tube OD on the Fox fork appears to be the same size as the SI bearing ID, I measured them at about 1.560. The top of the steerer tube, however, measures right at 1.500, making it about .060 smaller than the SI bearing ID. So can I use the SI bearing on the bottom and will I have to use the top half of a 1.5" headset for the top?

    I'd appreciate it if others who have switched to a regular fork would weigh in here so i would know how to proceed,

  4. #4
    LA CHÈVRE
    Reputation: Dan Gerous's Avatar
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    It wont be a right fit top and bottom. You need a proper 1.5" headset... It has to fit precisely, not just 'close enough'.

    One detail to verify too, Cannondale's SI headset outside diameter, coincidentally, is the exact same as the 1.5" standard that came out much later (their inside diameter, top and bottom, again, are not). But some 1.5" cups are too deep to fit old Cannondales. I don't remember what year did Cannondale started to ream their headtubes deeper to be able to accomodate 1.5" headsets... I know some Jekylls are okay, but I'm not sure if they were from the first year. What model year is your bike?

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  5. #5
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    I just checked the headtube on my frame, and it looks like the top and bottom are reamed to a depth of about .800. So is there a standard 1.5 headset that i can install in place of the SI bearing cups in the headtube? I'm a bit confused by the fact that there is about .060 difference between the bottom and top of the steerer tube OD on the fox fork. I assume the bottom 1.5 headset is machined to accomodate this larger OD?

  6. #6
    LA CHÈVRE
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    Is there a bearing seat on the Fox for the bottom bearing? In most cases, there is a race that must be installed on the steerer, against the fork crown and the bearings sit on that race, not directly against the fork. This might be why the size is not exactly 1.5" at the bottom.

    At 0.8" deep, I'd think most standard 1.5" headsets will work, but I'll let (and hope) someone else answers or recommends a headset model as I have never done the conversion myself... I'm in the camp thinking running anything else than a Lefty or Headshok is nonsense! You might find the specs on the dept of the cups on various headset maker's websites, Cane Creek, FSA, Chris King...

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

  7. #7
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    Ok i figured i might catch a little grief for using anything other than a headshok or Lefty at some point, but i wasnt quite ready to make the switch to a lefty along with a different front wheel etc. Anyway, the fox fork that i bought (used on ebay) has no race on the steerer. This fork came off a newer cannondale according to the previous owner, i think he said it was a 2010 model but i forget which one, so i might need to contact him to see if the fork had a race on it. I wouldnt think so, it doesnt look like the tube has ever had anthing like a race installed on it. Thats why i thought the fork would just install into the bottom SI bearing on my frame. I did try sliding it into the frame and it appears to be rather tight, like there might actually be a slight overlap in diameters, although measuring with a caliper they appear to be the same dia. I'm wondering what cannondale used for bearings/races on their frames that run fox forks with a 1.5 steerer?

  8. #8
    LA CHÈVRE
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    I was just teasing about the Lefty/Headshok...

    The race is headset specific, it comes with the headset and one headset's race is not necessarily compatible with another headset. The previous owner probably just kept the whole headset, including the race.

    DAN.GEROUS.NET : MOUNTAIN BIKING : CYCLOCROSS : ROAD :

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