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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Originally Posted by deacon mark
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.
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?