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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 02-26-13, 03:10 PM   #1
bjohn
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Ultegre 10spd BB a lot more friction than 9spd

My latest Ultegre 10 speed cranks/BB seems to have a lot more rolling friction (rotating with no chain) than compared to my old 9 speed Ultegre splined shaft BB, I'm assuming shimano have increased robustness, but with that came extra bearing / seal friction. Or is there a pre-load nut somewhere that can be backened off?
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Old 02-26-13, 03:21 PM   #2
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A new bottom bracket or a newly greased bottom bracket will naturally have more friction than a bottom bracket that needs grease. A crank will spin freely on a dry bottom bracket.
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Old 02-26-13, 03:22 PM   #3
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I think and have read on here that this is normal when new and then as it wears in a bit the friction goes away.

I felt the same thing when I went from 20,000km+ Veloce crankset that spun with no friction to brand new Chorus that did and was a bit disappointed.
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Old 02-26-13, 03:34 PM   #4
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If you're comparing external-type (10s) BBs to internal (9s) BBs, the former have more drag. You can't adjust the external Shimano BBs.
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Old 02-26-13, 04:09 PM   #5
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Don't worry about it. You won't notice the difference when riding your bike.
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Old 02-26-13, 07:06 PM   #6
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If you take the chain off and try to spin the cranks, how many times does the crank go around before stopping. Let me know this then I can give better answer.
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Old 02-26-13, 09:16 PM   #7
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Quote:
Originally Posted by deacon mark View Post
If you take the chain off and try to spin the cranks, how many times does the crank go around before stopping. Let me know this then I can give better answer.
Well this would depend on the force that was applied to the cranks... I find that if all is well set up there is a very small preload window with the Shimano (and a few other brands) external BBs. Too little and there is some end play (although you won't any get less bearing friction then this adjustment) and too much and there's increased drag. The trick is finding that happy medium where the end play is so little you only think it's still there. Having said that the external BB does have more seal friction then many cartridge types have when new. But don't fall into the trap of comparing an old cartridge unit to a new external one. That's apples to oranges. Andy.
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Old 02-26-13, 10:28 PM   #8
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thanks andy, this small preload window your talking about, i'm assuming this is not really a preload adjustment but it would have an effect on drag, Is there a torque setting for this? Be good if shimano specified a weight that you could hang from your pedal at horizontal, let it fall (no chain) and then specify an approx angle it has to come up the other side?
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Old 02-27-13, 12:53 AM   #9
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Seal drag in the BB doesn't amount to squat; consider the leverage your foot has on it at the end of the crank.

You will probably notice the increased stiffness of the external BB / 26mm spindle though.

Quote:
Originally Posted by bjohn View Post
Is there a torque setting for this?
http://techdocs.shimano.com/media/te...9830607279.pdf

Last edited by Kimmo; 02-27-13 at 12:57 AM.
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