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Old 03-12-11, 04:21 PM   #1
stalag13
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VO Grand Cru BB instead of Dura Ace?

I've got a set of old Dura Ace 7400 cranks. I'm throwing them on an old Colnago, which has Italian threading in the bb shell. In lieu of buying a vintage, matching Italian threaded Dura Ace bb, I was wondering If I could go with this set-up instead:

Grand Cru BB with a 110 mm spindle length, and...
BB Spacer with a .7 mm width.

The original matching Dura Ace bb has a 112 mm spindle. I'm assuming it is symmetrical. The set-up above should put me within .3 mm, which should be close enough, correct? Or is that wrong? Would really like to avoid shelling out the money for an original looseball Dura Ace bb that's probably gonna get worn out quickly on the streets...
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Old 03-12-11, 04:33 PM   #2
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A cup/cone BB won't wear out any sooner than a cartridge bearing unit if it's installed and adjusted properly. But, I see the attraction (price, easy installation) of the VO unit. I've used them in English, Italian and French threading.

I think your math is off by 1mm, but you're right in that you should be close enough. I believe the 110 spindle I have is actually marked 110.5. Buy two (2) of the spacers. If your crank arms are longer than 170 you might opt to buy one each of the following sizes: .7mm and 1.8mm.

Good luck!
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Old 03-12-11, 04:44 PM   #3
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A cup/cone BB won't wear out any sooner than a cartridge bearing unit if it's installed and adjusted properly. But, I see the attraction (price, easy installation) of the VO unit. I've used them in English, Italian and French threading.

I think your math is off by 1mm, but you're right in that you should be close enough. I believe the 110 spindle I have is actually marked 110.5. Buy two (2) of the spacers. If your crank arms are longer than 170 you might opt to buy one each of the following sizes: .7mm and 1.8mm.

Good luck!
Thanks for the advice Colonel. I was under the assumption that if a bb is symetrical, you only need one spacer on the DS to affect the chainline. So, from the center of the Dura Ace bb to the end of the spindle, the length is 56 mm (half the length of the spindle). With the set-up above, I would be at 55.7 mm. This was how it was explained to me, anyways. Just want to make sure the explanation I've got in my head is correct.
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Old 03-12-11, 04:50 PM   #4
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Thanks for the advice Colonel. I was under the assumption that if a bb is symetrical, you only need one spacer on the DS to affect the chainline. So, from the center of the Dura Ace bb to the end of the spindle, the length is 56 mm (half the length of the spindle). With the set-up above, I would be at 55.7 mm. This was how it was explained to me, anyways. Just want to make sure the explanation I've got in my head is correct.
You're math is correct. Mine was not.

Yes, you only need one spacer to affect the chainline, but what if it is not quite enough? It is then you'll wish you had another. I've been there. My issue was not with the chainrings hitting the chainstay, but rather the inside of the end of the crankarm hitting the chainstay. This was on a crank with an extremely low Q factor, however. I'll stay with my original answer of 110mm spindle and a couple or three spacers. They're nice to have around.
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Old 03-12-11, 05:18 PM   #5
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The Italian DA 74xx spec is 113mm [English is 112mm]
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Old 03-12-11, 05:24 PM   #6
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Note-- I think the 7400 crank is technically ISO and not JIS. It was the only crank where Shimano did that. There is a thread on this somewhere.

EDIT: Found it

http://www.bikeforums.net/showthread...red-BB-spindle
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Old 03-12-11, 05:38 PM   #7
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Sonofa...ok, does anyone know of a sealed cartridge unit that I could use?
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Old 03-12-11, 06:23 PM   #8
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Note-- I think the 7400 crank is technically ISO and not JIS. It was the only crank where Shimano did that. There is a thread on this somewhere.

EDIT: Found it

http://www.bikeforums.net/showthread...red-BB-spindle
Looks like the pics in post 21 show the 74xx to be JIS, not old Campy. And if the spindle was ISO the cranks would sit even further inboard than the arms on the Campy spindle.

If I get motivated I have a couple UN5x BBs and a DA 74xx spindle, along with a crank. I'll measure them up a little later tonight.
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