Technical > Transmission

Crank not turning smoothly in EBB.

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rafiki:
After reversing the chainring and sprocket and fitting a new chain I have noticed that the crank isn't turning at all smoothly in the EBB. Can the EBB be serviced/lubricated or is this going to be due to wear or damage?

Danneaux:
Brian, do you mean the eccentric is difficult to move/adjust for chain tension? If so, the eccentric needs to be lubed so it can more easily turn in the frame's bottom bracket hanger. Grease or anti-seize will prevent future galling between the aluminum eccentric and steel bottom bracket hanger.

If the eccentric has been adjusted a number of times so fresh indents have been made too close together, it can make it difficult to rotate the eccentric for adjustment and once rotated, may not easily hold adjustment. Solution here would be to replace the eccentric in this case. The damage would be visible in the form of a number of closely spaced divots in the edge faces of the eccentric.

If instead you find the cranks are not spinning freely or smoothly on the bottom bracket bearings (in the eccentric), then you would need to replace or service the bottom bracket depending on if it is a cartridge bb or one that can be opened and serviced.

Best

Dan.

rafiki:
Hi Dan. It's adjustable OK. The cranks are not spinning freely in the BB. Can I tell which type of BB I have without dismantling it?

geocycle:

--- Quote from: rafiki on August 30, 2018, 01:14:30 pm ---After reversing the chainring and sprocket and fitting a new chain I have noticed that the crank isn't turning at all smoothly in the EBB. Can the EBB be serviced/lubricated or is this going to be due to wear or damage?

--- End quote ---

Poor you, sounds like a whole raft of trouble you've had to deal with!  So all you have done is take the cranks off the square taper bottom bracket using a crank tool?  If it worked OK before, it is hard to imagine how removing might have damaged anything.  I assume the cranks are properly seated on the tapers.

If standard and original our BB is probably a Shimano UN55 or UN72.  The problem is that they come various flavours to do with axle length, diameter and how much sticks out left and right.  I don't think there is anything visible at the ends so it would have to come out, but maybe a call to SJS is in order?

Did you get that seized seatpost shifted? I picked up that woe on another forum.  The CTC folk have been discussing stuck posts and the name of a specialist remover The Seatpost man came up in Chorley Lancashire.

geocycle:
Two further thoughts:  I assume this is with the chain off?  If the chain was too tight it could cause this problem.  Also a long shot, but undo the eccentric bolts with the chain off and see if it persists -there's an outside chance the BB might be under pressure.

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