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donkpow

A problem for your attention.

Question

Installing an octalink bottom bracket in a a standard BB shell. When installing the right side 'nut', the nut runs in and pulls up tight. When installing the left side nut, the nut runs and pulls up tight. However, when both nuts are run all the way up, there is binding in the rotation of the crank. The BB cartridge I pulled out of this bike was worn out, perhaps prematurely. I currently have the left side nut fully installed and the right side not fully pulled in. Say a couple of rotations from its proper place.

What's your wild ass guess on the problem?

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...if the shell is 68mm in width, do you have a 68mm BB unit, or is it one of the 73mm ones ?

 

My only other suggestion is that maybe someone stuck one in there that is too short in spindle length some time in the past, and you need one that goes longer.

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It is the standard 68 mm shell. I am the person that put the new Octalink BB cartridge in and it is the correct component. I removed a square taper cartridge, also a correct component even though it had failed.

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...you run the drive (right side when astride the bike)side all the way in before you then attempt to seat the other cup (which is what I presume you're calling a "nut").

The non drive side does not need to enter fully into the BB shell, and often does not.  If you have the cartridge poorly centered in the shell (not side to side, but centered relative to the shell circumference), it can cause binding because one or the other of the cups is pressing on the bearing cartridge surface.  Try backing out the left side, fully seating the right side, making sure the left side cup tapered interior edge is still a tapered shape and not distorted, and try again.

 

Only torque in the left side until the tapered inside edge locks the cartridge in place, centered in the shell.

 

That's all I got, unless you can actually see someplace where the crank itself is interfering with the shell or frame.

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I've gone through that kind of stuff and am currently not running the left side nut of the cartridge all the way in. At least the spindle spins without binding. 

The conclusion I have drawn is that the shell needs to have the threads chased. The problem may be when you run the nut all the way up, the nut gets cocked causing the binding. Technically, I'd like to find some way to check alignment of the existing threads to see if they were properly cut at the factory.

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On 2/3/2018 at 4:15 AM, donkpow said:

I've gone through that kind of stuff and am currently not running the left side nut of the cartridge all the way in. At least the spindle spins without binding. 

The conclusion I have drawn is that the shell needs to have the threads chased. The problem may be when you run the nut all the way up, the nut gets cocked causing the binding. Technically, I'd like to find some way to check alignment of the existing threads to see if they were properly cut at the factory.

...all the better BB thread chasing tools have a pilot shaft, which automagically aligns both sides' threading in the shell. It aligns the threads as it cuts.

You can buy them relatively cheaply now from Europe, for like a hunnert fitty bucks.  The one you see a lot in shops is the park, which works well , but is waaay overpriced.

 

unior_1698_bottom_bracket_tapping_tool_b

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1 hour ago, Reverend_Maynard said:

Have you tried reinstalling the old to see if you can make it bind the same way? =or= Do you have another similar BB laying around you could try?

 

I have. In fact the one I took out was binding and was ridden to the point of premature failure.

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