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External bottom bracket - how much friction should there be?
On the weekend I installed a brand new XTR bottom bracket and XT crankset into a new frame. Before installing the chain I was interested to see how freely the crankset would spin. To my surprise I found that the crankset could not maintain momentum as soon as I stopped turning it.
I've taken off similar components on other bikes and never thought to see how freely the crankset spins. Has anyone tried this themselves and had different results? If so, any suggestions on why my set up seems to have a lot of friction.
Before people ask:
- I greased all the parts that need to be greased.
- No I don't have a torque wrench (but the pinch bolts are probably not over tightened).
Thoughts?
Andrew
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Has the bottom bracket on your frame been faced?
If the two faces are not parallel the spindle isn't straight which put load on your bearings.
Yeah if you have the cranks installed and it wont spin easily it sounds as though the bearing are loaded up somehow.
I can only suggest remove and install again to see if everything is in its correct place and aligned up straight.
Could also be incorrect amount of spacers used for shell width. Did the crank spin freely before you tightened the left crank?
How much preload have you put on with the funny-shaped nut that goes in the non-drive side end of the shaft? You only need enough to take out any slop - it would be well less than 1Nm of torque required on it.
If you have too much, it binds up the cranks quite easily.
I will check alignment and the shell width tomorrow night when I have a second go at getting them 'right'. I ma pretty sure the frame was faced as it was a warranty replacement from Scott.
I made sure not to over tighten the funny shaped nut on the non drive side.
I'd like to know why Shimano decided to change the crank bolts over to a torx key, just another tool to carry around when I go for a ride now...
Andrew