Non-Standard BB Shell?
03-13-23, 11:20 AM
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Non-Standard BB Shell?
I recently picked up an '85 (I think) Rocky Mountain Giro road bike which I've taken apart. When I went to install a different BB, I found that the diameter of this shell was slightly bigger than normal. I've never seen this before. Has anyone had a similar experience?
03-13-23, 11:24 AM
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If by some chance that the frame was built in Italy it might have an Italian threaded bottom bracket shell. What is the width of the bottom bracket shell? If it is 70 mm that would be a clue
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03-13-23, 01:26 PM
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Maybe it had a Ashtabula one piece crank in it originally. Those are way bigger shells IIRC. But it's been over a dozen years since I had anything with a Ashtabula crank?
What did you take out of it? Or was it with no cranks?
What did you take out of it? Or was it with no cranks?
03-13-23, 04:53 PM
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Looks like it's an Italian BB shell on a Canadian frame, and the dropouts are Campy, guess I just got confused. That happens a lot.
03-14-23, 05:52 AM
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Some mountain bike BB shells are 73mm vs the 70mm IT or 68mm BSA
03-14-23, 09:42 AM
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Originally Posted by VtwinVince
I recently picked up an '85 (I think) Rocky Mountain Giro road bike which I've taken apart. When I went to install a different BB, I found that the diameter of this shell was slightly bigger than normal. I've never seen this before. Has anyone had a similar experience?
03-14-23, 09:45 AM
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Originally Posted by Germany_chris
Some mountain bike BB shells are 73mm vs the 70mm IT or 68mm BSA
03-15-23, 09:39 AM
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Originally Posted by VtwinVince
I recently picked up an '85 (I think) Rocky Mountain Giro road bike which I've taken apart. When I went to install a different BB, I found that the diameter of this shell was slightly bigger than normal. I've never seen this before. Has anyone had a similar experience?
Last edited by alcjphil; 03-15-23 at 05:03 PM.
03-15-23, 02:45 PM
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The cynic in me says there can't be any non-standard BBs. If you took a bear's claw and stuck it through a piece of metal, it would surely be within tolerance for at least one of the many BB standards!
