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Old 02-20-06, 01:41 PM   #1
acrafton
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Compact Crank and Bottom Bracket

Hey. I am buying a compact crank but am confused about the bottom bracket. The bikes that I would use this on are currenlty Dura-Ace and Ultegra and I would like to be able to move it from one to another if needed. One of the compact crank's comes with its own bottom bracket and another one has an ISIS bottom bracket interface. A few questions:

Is it better to go with one over another?
Is dura-ace and ultegra compatible with the ISIS interface?
I am reasonably mechanical - can I install a new crank?

Thanks
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Old 02-20-06, 03:43 PM   #2
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Shimano never made an ISIS compatible crank. It's got to be Octalink, similar to but by no means the same as ISIS. In fact ISIS was developed to get around Shimano's Octalink design patents.
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Old 02-20-06, 04:39 PM   #3
acrafton
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Thanks.
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Old 02-20-06, 04:47 PM   #4
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Quote:
Originally Posted by acrafton
Hey. I am buying a compact crank but am confused about the bottom bracket. The bikes that I would use this on are currenlty Dura-Ace and Ultegra and I would like to be able to move it from one to another if needed. One of the compact crank's comes with its own bottom bracket and another one has an ISIS bottom bracket interface. A few questions:

Is it better to go with one over another?
Is dura-ace and ultegra compatible with the ISIS interface?
I am reasonably mechanical - can I install a new crank?

Thanks
If I'm reading this correctly, the bikes you currently have (and would use the crank on) are DA & Ultegra. I'm guessing this means the current cranks?

The Compact Crank (CC) you are considering comes either as an ISIS compatible or one of the external bearing things like Mega-Exo from FSA.

Assuming I understand you:
1. External bearings and the combined BB/Crank are lighter than separate, but to change cranks you then have to change bottom brackets. In your case you have to do that anyway, so personally I'd decide on cost. If you are a racer, I'm guessing the external provides some additional benefit, but I'm not sure what that is.

2. If you are talking about the derailleurs and shifting then yes, no problem. If you currently have ultegra/DA cranks, your bottom bracket is likely octalink (as previously suggested) and you would need to change your bottom bracket to an ISIS bottom bracket if you go with the ISIS version. If you go with the Mega-Exo type, then you have to do that anyway.

3. Yes you can, assuming you have the correct tools. (crank extractor, 8mm allen wrench, bottom bracket tool & probably a decent ratchet set, torque wrench if you really want to do it right & whatever is requried for the external bearing cranks should you go that route).
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