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Old 09-21-06, 09:13 AM   #1
mortytheclown
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Standard BB size?

Does anyone know-
Can I fit a Campagnolo bottom bracket (circa '86, '87) onto a Centurion Le Mans from the same period? My frame is outfitted with Shimano BB and components at present, but I'd like an upgrade.

Thanks!
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Old 09-21-06, 09:17 AM   #2
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You can, but you'll need new cranks for a campy BB.
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Old 09-21-06, 09:37 AM   #3
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Quote:
Originally Posted by mortytheclown
Does anyone know-
Can I fit a Campagnolo bottom bracket (circa '86, '87) onto a Centurion Le Mans from the same period? My frame is outfitted with Shimano BB and components at present, but I'd like an upgrade.

Thanks!
It depends...

If the Campagnolo has English threading it should work. However, if it is a different threading it won't. It is my understanding that Campagnolo made BBs with different threading to be able to provide components for a variety of bikes.

Also, the previous poster has a point on the cranks, there are different tapers on the BB as well from what I have read in the forums.
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Old 09-21-06, 09:37 AM   #4
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Quote:
Originally Posted by mortytheclown
Does anyone know-
Can I fit a Campagnolo bottom bracket (circa '86, '87) onto a Centurion Le Mans from the same period? My frame is outfitted with Shimano BB and components at present, but I'd like an upgrade.

Thanks!
Many Campy BBs are Italian threaded, while most Shimano BBs are English/ISO threaded (but both companies make both). You'll need to make sure that the threads match those on your frame. Your frame is 99% guaranteed to have English/ISO threads since it's Japanese-made in the 80s.

As for the different taper on ISO/JIS BBs (which operator pointed out): in theory you can't use one type of cranks with the other because the width of the taper is slightly different, although the angle is the same. However, such experts as Sheldon Brown say that it's generally safe to do: http://groups.google.com/group/rec.b...c08716cbc6917e
It's what Sheldon refers to as a "Class B" fit... meaning that you can switch your cranks from JIS to ISO taper or vice versa, but shouldn't repeatedly go back and forth.

Last edited by moxfyre; 09-21-06 at 09:42 AM.
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Old 09-21-06, 09:39 AM   #5
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There are multiple different shell sizes/threadings - diff standards to which frames have been made. The bottom bracket has to have the same shell size and threading as the frame. Sheldon Brown has a good run-down of the various standards.
By far the most common (especially since the early '80's) is the British/ISO 68mm standard. Your Centurion will be this standard (as were nearly all Japanese-made bikes), but it's not guaranteed that your bottom bracket will be.

And as operator says, a Campy BB will only work with a Campy crank (or a few others built to the same standard). There are two main standards of square-taper crank/bb interface design. ISO is the Campy standard, whereas the JIS standard is used by Shimano and Japanese makers, and is far, far, far more common.
If you'd need to buy a new Campy crank (and one that has proper chainline with the width of bottom bracket that you have), it's probably better for you to just sell the BB on eBay. But if you already have a crank and BB combo, and it's English-threaded, then it makes sense to put it on your Centurion.

edit: I got in a conversation with my officemate and y'all beat me to the response
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Old 09-21-06, 09:49 AM   #6
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However, such experts as Sheldon Brown say that it's generally safe to do:
This is probably one of those rare moments when i'll have to disagree with Sheldon. I have seen cranks ruined this way. Look at it this way, campy chorus/record crank exceeds the bb's cost by about a bajillion times <- slight exaggeration.

I'd do it if i was real short on budget and had an inexpensive crank, but I wouldn't on a nice roadbike.
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Old 09-21-06, 09:49 AM   #7
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I will have the cranks to fit this BB, if I can find out the threading before I purchase the parts. How can I tell the difference between Italian & English thread?
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Old 09-21-06, 09:53 AM   #8
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Originally Posted by mortytheclown
I will have the cranks to fit this BB, if I can find out the threading before I purchase the parts. How can I tell the difference between Italian & English thread?
Measure the width of your frame's BB shell with calipers: 68 mm=English, 70 mm=Italian. To double check you can try unscrewing the right-side BB cup. If it's English you'll have to turn it CLOCKWISE to loosen it, if Italian you'll have to turn in COUNTERCLOCKWISE.

This is totally unnecessary though. Your frame is Japanese and made in the 80s. The Japanese builders used English/ISO BB threads because they're a superior design: Italian BBs are prone to unscrewing themselves because of precession. That's why English BBs have the reverse thread on the right cup.
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Old 09-21-06, 09:57 AM   #9
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Originally Posted by operator
This is probably one of those rare moments when i'll have to disagree with Sheldon. I have seen cranks ruined this way. Look at it this way, campy chorus/record crank exceeds the bb's cost by about a bajillion times <- slight exaggeration.

I'd do it if i was real short on budget and had an inexpensive crank, but I wouldn't on a nice roadbike.
I agree that it's basically unnecessary in practice

If you buy Campy cranks, you're by definition not short on cash, so buy the stupid overpriced Campy BB. And if you buy cheap JIS cranks, you can get a cartridge BB for about $12, so there's little reason to use the wrong BB.
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Old 09-21-06, 10:55 AM   #10
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Thanks for the help, all!! I'm going to check these parts out tonight to see if they'll fit and now I know what to look for. Hope they fit, it seems like a sweet deal
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