Within 3-5 mm how important is chain line on a multispeed drivetrain?
I'm building up a hotrod 12 speed from a handbuilt 531 American frame using some favorite but unmatched components. I'm using some odd Italian, Japanese, American and French parts which don't ordinarily go together. Now, I'm almost finished and have to decide on the "correct" BB for a lovely Topline double crankset.
The Topline is ISO taper (I presume) and fits differently on every BB I've tried - Campy, Shimano, Hatta, Sugino, Suntour, Edco. There's as much as 3+ mm difference in depth of fit because of square taper differences.
Also, there are various axle lengths to consider, from 112 to 116 mm.
I think that if I have sufficient clearence from chainstay AND have sufficient depth of fit on square taper that the variance in chainline can be compensated for in available derailleur adjustments.
Sheldon says that in spite of the JIS/ISO/? differences he's never had a problem compensating. I tend to agree (in theory).