square taper bottom bracket calculation

[busdennis]

im building a single speed and to get a good straight drive line i need to move the crank 2mm to the right. the bottom bracket is 113mm long so do i need a bottom bracket 115mm (ie all the extra lenght goes to the chainring side) or 117mm (the extra lengh is shared 50% on each side)

thanks for any help

robert

 

[RecordAceFromNew]

im building a single speed and to get a good straight drive line i need to move the crank 2mm to the right. the bottom bracket is 113mm long so do i need a bottom bracket 115mm (ie all the extra lenght goes to the chainring side) or 117mm (the extra lengh is shared 50% on each side)

thanks for any help

robert

If you are talking about Shimano UNxx BBs you need the 118mm. It will be 2mm longer on the drive side and 3mm longer on the non-drive side. The 115mm is no longer on the drive side and I think 117mm ones don't exist except as a E variant of the 116mm BB for E-type front mechs.