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F = ma
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Discussion Starter · #1 ·
I purchased a correctly sized square taper shimano bottom bracket from my LBS (68mm for a '06 Kona Kikapu).

I can hand thread either side in all the way so I know this isn't a mis-threading issue.

But...after I thread the drive side in all the way, the other side will only thread in 7/8 of the way (leaving about 1/4" sticking out of the shell).

I am at a loss. Did I get a mis-labeled BB or and I screwing something up. I bought my bike as a frame and so I don't have a previous BB to compare to.

Thanks for any help you can give me. I am not thrilled with the service at any of my local shops, so I want to take it in only as a last result.:)
 

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It's possible that the threads in your frame are not perfectly alligned with each other. Each cup threads in easily by itself, but the mis-allignment becomes apparent when both are threaded in with the cartridge connecting them. It won't feel like a hard stop, but the thread will become increassingly harder as you go deeper. If that's the case you'll have to apply some increased torque to reach the final position, but don't get carried away. Use some judgement here and do not apply enough torque to jam it in, or damage your tools, since you'll want to get it apart again. If in doubt quit while you're ahead.

This is a common problem on new frames, but can only be corrected (not always, only if just slightly mis-allignment) by a skilled mechanic with the right tools. Since it's new, I suggest you let whoever sold you the frame deal with the BB installation, and if the mis-allignment is severe consider the frame defective and ask for a replacement.

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A bit of background. For many decades BB threads were tapped on both sides simultaneously with taps connected to each other by a rigid shaft. This ensured that the threads would be perfectly alligned with each other.

In the last few years manufacturers have moved away from this technique and threaded the shell one side at a time. There's nothing wrong with the new practice, which usually produces excellent threads, but it lacks the bulletproof reliability of the old way. In my opinion, a minor example of progress going backwards.

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There are other possibilities, for example if you have a loose bearing traditional BB you might have the ball retainers in backwards. Or the BB shell is less than 68mm wide.

Since It's all new, I suggest you not get in any deeper (no pun intended) and let the seller or a pro deal with it. You shouldn't have to.



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Did you compare the width of your BB shell with the BB assembled outside of the shell? Put the non-drive side sleeve on the BB until it bottoms and then hold the BB assembly under the shell with the drive side shoulder flush with the shell face. Does it stick out the same amount? Can you measure the width of the shell and verify it is 68mm?
 

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Yep, what steiny said.

Also measure that distance between the flanges of the uninstalled BB.

Is it 68mm, what's the actual marking on the BB...not the box.

Is the frame BB shell width cut to accept a front derailure mount between the drive side sleeve and frame? (narrower than 68mm).

Check the frame specs for recommended Front derailure type.

Let us know what you find...

Tilos

(why all the BB questions lately?)

steiny said:
Did you compare the width of your BB shell with the BB assembled outside of the shell? Put the non-drive side sleeve on the BB until it bottoms and then hold the BB assembly under the shell with the drive side shoulder flush with the shell face. Does it stick out the same amount? Can you measure the width of the shell and verify it is 68mm?
 

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Que je suis bete!
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Two things come to mind. One, 1/2 inch is left hanging out. This is more than twice what a spacer ring would take up if the bottom bracket were a 68/73 design. So there probably is a problem, unless you have some huge downhill BB or something. I just installed a SKF Isis this weekend. In the instructions, SKF said that if the non drive side doesn't seem to want to go in, back the drive side out a little bit and then try the non-drive side again. Then retighten all the way, the drivel-side first. Did you put some grease or anti-seize on the interface between the non-drive side lockring and the driveside barrel? This might help.
 

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F = ma
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Discussion Starter · #6 ·
Thanks for all the help guys. FBinNY was spot on.

I did goop up the interface between the sides and then applied extra foot-pounds to the installation. It was scary, but it popped into place. :thumbsup:

Usually when I apply that kind of force to my bike, I snap off something expensive.

Thanks again!
 
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