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Triple Bottom Bracket Question

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Triple Bottom Bracket Question

Old 01-22-10, 08:43 AM
  #1  
cpsqlrwn
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Triple Bottom Bracket Question

I am shopping for a triple bottom bracket and I am seeing 2 sizes, 111mm and 115mm. Is there an advantage to one over the other in terms of smooth shifting functionality. What comes to mind (and I realize we are talking about very small distances here) is perhaps from an alignment standpoint that one might be better than the other in terms of ring to ring movement on the front and also the reduction of cross chaining. I would probably be using this with a Racing T crankset. Perhaps this is a stupid question, but I remember being told that the only stupid question is the one not asked. Thanks for any helpful comments.
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Old 01-22-10, 08:53 AM
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The shorter spindle is for bikes with a 28.6mm seat tube. The longer spindle is for all others. If the shorter spindle is used where it's not supposed to be, the lever arm on the FD will hit the seat tube without shifting the chain to the little ring.
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Old 01-22-10, 11:27 AM
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Originally Posted by DaveSSS View Post
The shorter spindle is for bikes with a 28.6mm seat tube. The longer spindle is for all others. If the shorter spindle is used where it's not supposed to be, the lever arm on the FD will hit the seat tube without shifting the chain to the little ring.
I have a 28.6 seat tube so I could use either one. So going back to my original question, is there any advantage in terms of positioning/alignment (less cross chaining, ease of shifting on the front, etc.) to using the longer one or should that be avoided?
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Old 01-22-10, 02:26 PM
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First, you would better off asking this in the Bicycle Mechanics forum.

Second, the principle is that you want the front chainline to match the rear chainline if possible, but it's not always possible with a triple.

4mm will make a difference but the Campy spec difference of 1.5mm double-to-triple won't. IIRC, the Racing T wants a 45mm fr. chainline and you will want the 111 mm spindle. (I assume you're buying a contemporary Campy BB?).
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