I wish to upgrade the fork on this bike:


However I see fork offsets offered in 44mm and 51mm. I don't see any markings on the fork to indicate. Any other ways to know maybe via head tube angle?

  • Check the stickers on the back of the fork legs
    – MaplePanda
    Commented Apr 23, 2022 at 8:23

1 Answer 1

  • For a fork whose manufacturer provides a serial number lookup tool on their web site, usually the information can be found there.
  • Just measure it with a pair of plumb bobs. Put the bike or fork in a repair stand and use a level to make the fork perfectly vertical (steerer or stanchions perpendicular to the ground). Run one plumb bob's string down the center of the star nut and put something conical inside to center it in the star nut, then tie it off. Put the bare axle or QR in the dropouts and use a loop and knot on that plumb bob's string such that the line hangs down from the center. Then measure the horizontal distance (shortest observable distance) between the two strings.
  • You can do it in photo editing software or CAD by pulling the stem to get your steerer centerline and angle, drawing in a parallel line that bisects the axle center point, and then getting the distance between those lines. Tape a ruler near the focal center for scale.

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