Calculating bottom bracket spindle width
michaelmichaelmichael
Posts: 13
in Workshop
I’ve got an old set of square taper FSA tempo cranks (2x) that I want to swap from a single speed 120 OLD bike to a 1x10 135mm OLD one. Any tips on how to calculate the spindle width for correct chain line? I can’t find anything for that model on the manufacturers website, and i don’t think measuring the one on the single speed will work with the different chain line.
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Comments
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For 1x10 on a 135mm frame, your chainline should be somewhere around 49mm. Source: https://www.oneupcomponents.com/pages/understanding-chainline-for-optimal-1x-conversions-boost-and-non-boost
This is the measurement from the centre of the seat tube to the centre of the chainring. Measure this distance on the current setup and compare it to 49mm. If you measure (for example) 45mm, you'll need to add 4mm onto each side to keep it symmetric, so add 8mm to the current spindle length in total. 1-2mm either way won't matter much, so just get the closest available spindle length.0
