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  1. #1
    RoadBikeReview Member
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    IS52 lower headset bearings variance

    I was trying to swap in a new lower headset bearing on my integrated 1.5" frame and was astonished to find out that there's a big variation in outer diameter and stack.

    Bearing from a Giant frame (FSA headset) was 51.8 mm diameter. Easy to slide in but a bit loose.

    Bearing from Specialized headset was 52.0 mm exactly. Slid in easy and fitted well - required a bit of force to remove.

    Cane creek bearing was slightly larger than 52 mm. Inserted ok but required a tool to remove. The headtube impinges on the fork with this bearing.

    Stack height on the Cane creek was only 6.5 mm but the others were 8 mm. Makes a difference to fork crown clearance.

    Any idea why the big difference in tolerances and stack height? Can one swap IS52 bearings without worrying?

    Why do some manufacturers use 45 deg bearing angle and other 36 degrees? Can one measure this angle on an integrated crown race steerer - I can't judge by eye.

    Spent quite a while searching and there is very little info out there. Talked to LBS mechanic and they weren't much help either.

  2. #2
    'brifter' is a lame word.
    Reputation: cxwrench's Avatar
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    Quote Originally Posted by carlosflanders View Post



    Any idea why the big difference in tolerances and stack height?

    Because.
    I work for some bike racers
    I've got some bikes, some guns,
    and a bunch of skateboards

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