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Old 12-27-06, 01:27 AM   #1
seaneee
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68mm BB in 70mm Shell?

I posted this in another forum, but I hoping to get a more exact answer here.

I have an old 70's Concord. It has a 70mm BB shell, but it's english thread. Could I make a 68mm bottom bracket work? Or even a 73mm? Any ideas? Thanks.
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Old 12-27-06, 10:03 AM   #2
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If you are going to use a Shimano UN-7X or UN-5X square taper cartridge bb, you can probably just get a 68 mm one and screw the nds cup in the extra 2mm since that cup doesn't shoulder against the bb shell
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Old 12-27-06, 10:26 AM   #3
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I had the same problem, I used a 68mm bb and tightend...it works fine for me
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Old 12-27-06, 11:15 AM   #4
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Get the BB shell faced down to 68 mm. Make sure both sides of the shell are symetric or your chain line will be off.
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Old 12-27-06, 02:04 PM   #5
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Quote:
Originally Posted by Nessism
Get the BB shell faced down to 68 mm. Make sure both sides of the shell are symetric or your chain line will be off.
That can be done but it's a lot of metal to remove and the LBS is going to charge a fair bit to cover the wear and tear on his facing tool. A '70's concord probably isn't worth what it will cost.

The Shimano 68 mm square taper cartridge bottom brackets I recommended will fit with no modifications and a 1 mm "error" in the chain line is a non-issue.
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Old 12-27-06, 03:09 PM   #6
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That can be done but it's a lot of metal to remove and the LBS is going to charge a fair bit to cover the wear and tear on his facing tool. A '70's concord probably isn't worth what it will cost.
It won't cost much, if any, more to have the shell cut down to the proper size. I've faced a fair number of shells before and the cutter will shave a couple mm's of material pretty quickly.
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Old 12-27-06, 03:42 PM   #7
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It won't cost much, if any, more to have the shell cut down to the proper size. I've faced a fair number of shells before and the cutter will shave a couple mm's of material pretty quickly.
actually it looks like it wont work. I took a closer look at the shell and the chainstays are REALLY close. I would be concerned with strenth issues even with 1mm. Nashbar has a $5 bb i may try or I may have the threads removed an go with a YST that will fit both 68 and 70mm, both pretty inexpensive options.
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