• What am I missing here,

    Left is a 68x107 un55
    Right is a 68x110 un55

    Driveside axle projection is identical, the extra length on the 110mm is all on the nds.

    Surely it should be 1.5mm either side?

  • Square taper BBs aren't necessarily symmetrical. The detailed specs will tell you what the DS and NDS protrusion will be.

    The 110 seems to be particularly asymmetrical. Presumably it's designed for a specific chainset model - maybe to push the left crank out to match the extra width of a triple on the right hand side.

  • Can’t seem to find this info from shimano themselves but someone in this thread has posted a chart with measurements of a load of different sizes of un55 and it does seem the 110mm is a bit of an anomaly being 3.5mm longer on the nds than the ds, all the other sizes are 1mm or less of difference between the two sides.

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