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  • Why doesnt my shiny new freewheel extender thread onto a specialized 3 spoke

    Poor QC on the part of the manufacturer. They should test with a plug (SPNK) or ring (Specialized) gauge at least every tenth one off the lathe, and change the threading insert when they get out of spec. What they've actually done, in all probability, is not buy a gauge (they are expensive, even more so for cycle threads which aren't run of the mill for gauge makers), not change their threading insert often enough, and not check any of them. This approach is one you can get away with when doing short runs on free-cutting material with industrial grade thread fit tolerances. If you've been unlucky, you've got the last Specialized hub and the last SPNK adapter. The hubs will grow as the tool wears, and the adapter will shrink. Eventually you go past the tolerance band, and a little past that (about 0.0008" or 20μm past the ends of the standard tolerance bands for 1.375"×24TPI) you get zero clearance.

    Either that or something is just damaged or contaminated and you can fix it by ordinary "preparation for assembly" processes like cleaning and deburring.

  • Thanks for the answer. I checked the extender with a new bottom bracket cup and it fits perfectly. So it is the wheel that is off.

    I then "chased" the wheel thread with a steel bb lockring and I can fit the extender now.
    so maybe it was oxidation/dirt on the wheel.

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