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Old 11-19-07, 07:09 PM   #1
digitalbicycle
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Dura Ace FC-7402: which BB?

I just bought an 80s Faggin frameset (pics at http://bikeforums.net/showthread.php?t=363421) and am going to put a new Shimano 10 speed drivetrain on it. I have a set of Dura Ace FC-7402 cranks, which are 9 speed, but Sheldon Brown's site says there's no difference in the spiders b/w 9 and 10 speed, so if I get 10 speed chainrings I should be good to go.

I found on the internet somewhere that this crankset takes a 113mmx70mm Italian BB. Will a BB w/these dimensions give me a good chainline for a Shimano 10 speed cassette? I know that Shimano's BB-UN54 comes Italian threaded in a 113mmx70mm square taper, but I don't know how it stacks up to other BBs. Have other people had good experiences w/the UN54? If not, any other suggestions? Thanks.
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Old 11-19-07, 07:18 PM   #2
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You mean the frame takes a 113x70mm Italian Bottom bracket. Usually 113mm bottom brackets are for triple cranksets. If you have a triple crankset then your good but if you have a double the crank might sit out just a bit too far and you run the risk of derailing you chain.

If you have a double chainring crank try finding a 109mm x 70mm Italian bottom bracket. This will bring your chainline closer to your frame. This will eliminate extreme chainline angles and reduce the risk of derailment.
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Old 11-19-07, 07:26 PM   #3
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Originally Posted by vasracer View Post
You mean the frame takes a 113x70mm Italian Bottom bracket. Usually 113mm bottom brackets are for triple cranksets. If you have a triple crankset then your good but if you have a double the crank might sit out just a bit too far and you run the risk of derailing you chain.

If you have a double chainring crank try finding a 109mm x 70mm Italian bottom bracket. This will bring your chainline closer to your frame. This will eliminate extreme chainline angles and reduce the risk of derailment.
Thanks for the reply. I found the measurements for the BB here:
http://www.bikepro.com/products/bott...omptable.shtml

I assumed this meant that the crankset was only compatible with this size BB. If this is not the case, and spindle length will vary w/frame, what's the point of that compatibility table?

Also, the crank is a double.
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Old 11-19-07, 07:44 PM   #4
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If this is not the case, and spindle length will vary w/frame,
Uh. Why would this be true. Spindle length 'x' gives chainline 'y'. That doesn't change on any bike. Unless the crankset hits the chainstay and you have to get a longer bb.
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Old 11-19-07, 07:50 PM   #5
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7402

7402 should be 8spd

112-113 bb

http://www.sheldonbrown.com/bbsize.html#dura
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Old 11-19-07, 08:06 PM   #6
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7402 should be 8spd

112-113 bb

http://www.sheldonbrown.com/bbsize.html#dura
Damn, I don't know where I got the idea that 7400 was 9 speed. Are there going to be any compatibility problems using the 7402 crankset with a newer 10 speed drivetrain, provided I buy new chainrings?
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