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Do I need a longer axle BB when switching from an Ultegra dbl to triple set-up? I have 109.5 mm BB-6500 and a 9 spd Ultegra triple crankset... Will this work or will my chainline be off? Can i add some adjustment shim to the drive-side to in effect create the extra 9 mm?

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You're asking for trouble. The crank will probably hit the chainstay if you don't switch them out and there's no shim to correct that much, it's almost a whole centimeter! Just grab a 105 BB, they're not that expensive.
 

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no..

The reason this is unlikely to work is that very few frames provide enough clearance between the little chainring and the chainstay.

The front derailleur may also lack the travel to move far enough to the left, to execute the middle to little ring shift.

The normal triple chainline is 46mm to the center of the middle ring. That's within 1mm of the normal position for the big ring on a double.
 
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