Crank arms not spinning freely

[Cyclenon]

Hi there,

the crank arms on my bike (Allez Sport) do not seem to spin freely, certainly not as freely as my older Trek 7.3FX.There is noticeable resistance.

The Allez is pretty new (c. 5 months) and hasn't done that many miles yet.

Could it be that the seals on the bottom bracket still need time to "bed in"?
Otherwise what would you suggest the likely cause could be?

Thanks.

 

[accountantpete]

I take it you have taken the chain off and given the cranks a spin.

What type of BB do you have - Hollowtech II?

 

[Cyclenon]

Hi,

yep, took chain off; there's definitely resistance.

Not experienced enough to be able to identify a Hollowtech II.
The specs say "Shimano, outboard cartridge bearing, 68mm".

Here's a pic if it helps:

 

[accountantpete]

That's a Hollowtech II.

Ideally you need to take the cranks off (take off the large plastic screw and undo the two metal bolts on the left hand side and then pull apart).

Then get really technical by pushing your finger in the bearing hole and turning the bearings on both sides..

If it feels rough and difficult to turn then the bearings have gone.

If that is the case you then need to ask what has gone wrong.

 

[derrick]

Hi there,

the crank arms on my bike (Allez Sport) do not seem to spin freely, certainly not as freely as my older Trek 7.3FX.There is noticeable resistance.

The Allez is pretty new (c. 5 months) and hasn't done that many miles yet.

Could it be that the seals on the bottom bracket still need time to "bed in"?
Otherwise what would you suggest the likely cause could be?

Thanks.

Take it back to the shop get them to check it out, could be done under warranty.

 

[Cubist]

You do get a bit of bearing resistance, but it shouldn't be too hard to turn. Hollowtech BBs are a bit of a bugbear for bikebuilders, and it's easy to overtighten the bearing preload when installing the crank. Take the left hand crank arm off as ACP suggests, tapping the axle with a plastic faced mallet to remove the rest of the chainset from it's interference fit on the bearings, and slide it out. (you need to unship the chain from the chainrings first). Check the bearings for roughness or drag, and if they spin OK then reinstall the crank. Once you've got the left hand crank arm onto the splines you need to set the bearing preload with the black nylon insert. Use the proper tool or a 20p piece to turn it. Screw it in until it's finger tight and check the cranks for play by trying to rock the left hand crank backwards and forwards. If there's any movement turn the preload cap a quarter turn at a time until you eliminate any movement, no more . Then tighten the crank pinch bolts alternating between them until they're firmed up properly.

Overtightening the preload can seriously shorten the life of the bearings which aren't designed to take any sideways loading.

 

[wisdom]

In view of the bikes age i would be inclined to take it back to where you purchased it from and ask them to sort it for you.That way you dont void any warrenty should a problem be lurking.

 

[Cyclenon]

You do get a bit of bearing resistance, but it shouldn't be too hard to turn. Hollowtech BBs are a bit of a bugbear for bikebuilders, and it's easy to overtighten the bearing preload when installing the crank. Take the left hand crank arm off as ACP suggests, tapping the axle with a plastic faced mallet to remove the rest of the chainset from it's interference fit on the bearings, and slide it out. (you need to unship the chain from the chainrings first). Check the bearings for roughness or drag, and if they spin OK then reinstall the crank. Once you've got the left hand crank arm onto the splines you need to set the bearing preload with the black nylon insert. Use the proper tool or a 20p piece to turn it. Screw it in until it's finger tight and check the cranks for play by trying to rock the left hand crank backwards and forwards. If there's any movement turn the preload cap a quarter turn at a time until you eliminate any movement, no more . Then tighten the crank pinch bolts alternating between them until they're firmed up properly.

Overtightening the preload can seriously shorten the life of the bearings which aren't designed to take any sideways loading.

Thanks everyone.
And for those wondering this is a video showing how it's done:

View: https://www.youtube.com/watch?v=TCDcJ1W9Doo


View: https://www.youtube.com/watch?v=4BP3-XGWWqc