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Old 05-08-07, 01:45 PM   #1
JunkYardBike
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Campy Nuovo Gran Sport RD capacity

Plotting to build my '79 Trek 530 with Campy GS. Traded nlerner for a nice Nuovo GS RD (thanks Neal!).

What's the largest tooth cog this will handle? I'm hoping to get the lowest gearing possible using it. I've got an Atom 77 with a 24T low , and I'm guessing that's probably the largest it can handle?

I'm assuming the GS over the years had a similar capacity. If not, I can get a photo of the one I have. It's marked with an "M" ... not sure if that's a date code.

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Old 05-08-07, 02:03 PM   #2
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My 1960 Gran Sport can take a 26T large cog.
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Old 05-08-07, 02:20 PM   #3
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This might not help, but my '71 Nuovo Record is running a 29 tooth cog on the Continental.
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Old 05-08-07, 02:24 PM   #4
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Quote:
Originally Posted by pastorbobnlnh
This might not help, but my '71 Nuovo Record is running a 29 tooth cog on the Continental.
Whoa, looks like that thing's on the torture rack, and it's not even on the the largest cog!

Thanks for the responses...the bigger the better!
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Old 05-08-07, 03:23 PM   #5
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NR and nuovo gran sport are basically the same derailleur..
i've heard the largest cog they can handle is about 28/29T
moving the wheel back in the dropouts is supposed to help a bit..

i've also heard of people gaining a bit of capacity by swapping the 9T jockey wheels for 11T
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Old 05-08-07, 03:49 PM   #6
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yup pushing it back in the dropouts is often a necessity but I have run into this problem... if the seatstay isn't crimped and you put the axle to the back you can get chain rub (this is likely only to be and issue on late 70s bikes before they started crimping). So sometime you have to go to 5 speed if you want the 28/29 tooth... or you could spread the stay and add some spacers.
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Old 05-08-07, 03:55 PM   #7
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Patrick, I'm running a Campy GS derailleur on my Raleigh Competition with a 28-tooth max rear cog. Shifts onto that cog are no problem at all, but I should add that it's a 5-speed freewheel.

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Old 05-08-07, 04:28 PM   #8
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The standard accepted max capacity for that derailleur is 28t, but it can be made to work on the largest freewheel cog Regina made, a 31t, by playing with chain length and dropout position. If you had the chain length set short enough to make this work, you had to be careful how far up the freewheel you went when you were in the large chainring though. But, if you put a 50t/42t front chainrings on a Nouvo Record crankset, the Gran Sport/Nouvo Record design will work pretty smoothly on a 31t cog with a normal chain length. The closer the front chainrings get in size to each other, the smoother it will work.
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Old 05-08-07, 04:36 PM   #9
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Quote:
Originally Posted by skinny
The standard accepted max capacity for that derailleur is 28t, but it can be made to work on the largest freewheel cog Regina made, a 31t, by playing with chain length and dropout position. If you had the chain length set short enough to make this work, you had to be careful how far up the freewheel you went when you were in the large chainring though. But, if you put a 50t/42t front chainrings on a Nouvo Record crankset, the Gran Sport/Nouvo Record design will work pretty smoothly on a 31t cog with a normal chain length. The closer the front chainrings get in size to each other, the smoother it will work.
That makes sense. When I got my Raleigh International, the chainrings were 52/45 with a Regina freewheel that had a 31t large cog, and a Campy NR rear derailleur. I could get it to work on the workstand, but I never rode it with that gearing. But the previous owner obviously had-
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Old 05-08-07, 08:31 PM   #10
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Quote:
Originally Posted by coelcanth
i've also heard of people gaining a bit of capacity by swapping the 9T jockey wheels for 11T
Good, it's got Shimano wheels on it now, so perhaps that will help.

Quote:
Originally Posted by cyclotoine
if the seatstay isn't crimped and you put the axle to the back you can get chain rub (this is likely only to be and issue on late 70s bikes before they started crimping). So sometime you have to go to 5 speed if you want the 28/29 tooth... or you could spread the stay and add some spacers.
Seatstays are not crimped. The wheel is currently spaced for a 6 speed freewheel, so I suppose I could run a 5 speed with that spacing.

I think I'll try a 28T large and see how that works. Thanks for all the help!
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Old 05-09-07, 08:33 AM   #11
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Quote:
Originally Posted by pastorbobnlnh
This might not help, but my '71 Nuovo Record is running a 29 tooth cog on the Continental.
Your derailer hanger places the angle of the parallelogram considerably farther foward then that of a Campagnolo hanger on a forged drop - similar phenominon as if you moved the rear wheel farther back in the drops on a bike with a built in hanger.

-Kurt
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