Low car diet
Join Date: Aug 2007
Location: Corvallis, OR, USA
Bikes: 2006 Windsor Dover w/105, 2007 GT Avalanche w/XT, 1995 Trek 820 setup for touring, 201? Yeah single-speed folder, 199? Huffy tandem.
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If we were talking about older cranks/BB like square taper or Octalink, then you could get a shorter BB and get roughly the same chainline as you had before. With the newer Hollowtech II and integrated BB spindle, you're pretty much stuck with the chainline specified.
Chainrings are about 5mm center-to-center (EDIT: this is the spacing). A Triple has a chainline of 45mm, at the middle ring, which means the outer ring is at about 50mm. A double has a 43.5mm chainline, measured halfway between the two chainrings, so the outer ringsits at about 46mm.
If your FD can swing another 4mm out from where it currently is (with the H-limit screw backed out), it'll be able to get out to the triple's outer chainring.
Last edited by JiveTurkey; 03-23-11 at 03:44 PM.