1

I have an english-thread, octalink Shimano bottom bracket, and a new frame. The frame has been faced before painting.

I am not sure the BB is compatible with the frame.

When trying to install the BB, I greased the thread, screwed in the driver-side cup and tightened it. I do not have dynamometric wrench, so I just torqued hard, but not as hard as not to be able to undo it. Then repeated for the non-drive side.

The bearings had became stuck - only with great force could one spin the axis. I loosened both cups about one revolution each, until the axis began moving freely. Now both cups have some threaded surface visible. The cups are not tight at all.

Are stuck bearings when over-tightening the cups normal? The free cup (non-drive side) looks like it can go all the way inside the frame. Have I set my BB correctly?

UPDATE: This is my exact BB. I have identified the problem. The non-drive side cup presses against the white seal. The seal is stuck to the axis (which I think it should be), and sandwiching it between the cup and the BB body fixes it's movable flange causes excessive friction.

I am leaving the installation as described above. Will ride it a couple of hundred kilometres and report if any problems occur.

enter image description here

Improve this question
5
  • Did the BB come with a 1mm spacer to be omitted when used with a front mech that mounts at the BB?
    – Emyr
    Oct 4, 2013 at 9:49
  • @Emyr, no, it's just two metal cups, with a body, attached to the drive-side one. The non-drive-side cup does not have a lip, so it looks like I can screw it all the way in to the other cup.
    – Vorac
    Oct 4, 2013 at 10:05
  • Doesn't sound "normal" to me, assuming that this is a cartridge and not loose bearings. The cartridge should be stiff enough to resist tightening by anyone other than a gorilla. That said, it's normal for one cup (the right, usually) to be "fixed" and screwed all the way in, while the other is "adjustable" (and will sometimes be equipped with a lock nut). One would not expect the adjustable cup to necessarily go "all the way in", and, in fact, it's probably normal for 2-3mm of thread to show.
    – Daniel R Hicks
    Oct 4, 2013 at 11:06
  • Bottom bracket designed for 73mm shell, frame with 68mm shell? Otherwise, what Daniel said. (I've only seen locknuts on cup and cone BBs, not on cartridge ones, but I haven't got an Octalink.)
    – armb
    Oct 4, 2013 at 11:42
  • @armb, Thank you for the warning. I explicitly checked, and both the BB and the frame are 68mm.
    – Vorac
    Oct 15, 2013 at 9:35

2 Answers 2

Reset to default
2

Most components will have an instruction sheet detailing the reccomended torque. This is typically measured in Nm (newton meters). Torque wrenches can also be purchased that show you how much torque you apply.

Some components even have the reccomended torque value on the component itself. Checking other components will give you an indication of the difference in required torque in relation to your BB.

Improve this answer
1

Shimano recommend 50-70 Nm of Torque on both Octalink(yours) and square taper bottom brackets. If you do not have a torque wrench you can try to approximate it by remembering that 1Nm is approximately 1kgdm. So 50 Nm is 50kg at 1dm(10cm) or 25kg at 2dm (20cm).

Install the drive side first, and go slow as you approach what you believe to be the final torque, keep checking the spindle as you go. Going too tight will prevent the spindle from moving freely (even with only one side installed in my experience!?). Then install the non drive side. Keep checking the spindle as you tighten it gradually. If the spindle movement is hampered, unscrew the unit a quarter/half a turn and hope you didn't go way too far and damaged it.

Unfortunately Shimano does not state clearly if they mean 50-70Nm on both sides or just the drive side. It seems to me they mean only the drive side. Then I guess* you tune the compression of the unit by tightening the non drive side carefully and gradually(ending at less than 50-70Nm) and stopping before hampering the movement of the spindle.

*) My impression is that full torque on both sides will "lock" the spindle. I just realized this post is 10 years old.

Improve this answer
New contributor
WornChain is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.