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Ring/chainline question….(5 posts)

Ring/chainline question….TFerguson
Nov 17, 2002 3:27 AM
Is the inner chainring on a double and the center chainring on a triple in the same line? Both would have the same (2x) BB spindle length.
re: Ring/chainline question….LC
Nov 17, 2002 9:43 AM
No, usually the small ring on a triple is slightly inside the chainline of the small ring on a double. The middle ring will be slightly outside of the small double ring. The BB length is usally different between a double and triple to compensate for the difference.
Still not quite sure…TFerguson
Nov 17, 2002 12:28 PM
So if I moved the triple about 8mm in by using the same (double) BB, will the middle on the triple and the inner on a double be in the same place?
TF
Check out www.sheldonbrown.commadstork
Nov 18, 2002 7:46 AM
See his definition of chainline in the glossary. Provides specs for Shimano road and triple crank front chainlines as well as instructions on how to measure front and rear chainline. This will give you some numbers that can help you determine if this will work.

Something else to consider: if using the double BB, will the spider of the triple crank clear the chainstay?
...and another chainline thoughtmadstork
Nov 18, 2002 8:15 AM
I haven't tried this, but there are bottom bracket and freewheel spacers as small as 0.5mm that can help with chainline. I've seen these at lbs as well as www.thethirdhand.com .