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Old 03-25-06, 08:19 AM   #1
TJHOO
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Given same brand (eg Campy) and level (eg Chorus) of components, does a medium cage rear derailleur (rd) shift as smoothly as a short cage rd?

Any other downsides to switching to med cage?

Am asking b/c am looking for lower gears for climbing (Cat 1 coming up). Curr have 50/34 chainrings and 12-25. Looking at 13-29 which requires med cage rd.

Have campagnolo components.
This would be for Tarmac listed below.

Thx,
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Old 03-25-06, 08:26 AM   #2
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I would think that the medium or long cage might be a little slower shifting but still smooth. Chain slap on the chainstay can be a little more pronounced with a longer der. cage since you need a slightly longer chain to go through the wider range of cogs.
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Old 03-25-06, 08:29 AM   #3
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Quote:
Originally Posted by masi61
I would think that the medium or long cage might be a little slower shifting but still smooth. Chain slap on the chainstay can be a little more pronounced with a longer der. cage since you need a slightly longer chain to go through the wider range of cogs.
Thanks,

So the shorter the cage is, the the shifting is more:
-efficient?
-less likely to drop chain??
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Old 03-25-06, 08:35 AM   #4
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Shifting speed and "smoothness" are a function of the derailleur hanger location and the position of the upper (jockey) pulley. The length of the cage is immeterial.

Chain slap is also a non-issue unless your chain is much too long.

Chain drop is controlled by the derailleur limit screws. Again, cage length is a non-factor.

Add the longer cage rear derailleur and get the lower gears you want. There is almost no downside.
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Old 03-25-06, 08:37 AM   #5
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Yes, the shorter cage would be a little more efficient.
Not sure if longer cages are any more likely to drop the chain though. Short cages can drop the chain too. As I've gotten older and slower I have a newfound appreciation for a longer cage rear derailleur and triple cranks too. A quality rear derailleur will have several spring loaded pivots that will securely wrap up excess chain. If you follow the instruction sheet that comes with the derailleur and set it up properly, you should be fine.
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Old 03-25-06, 10:38 AM   #6
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On various forums several riders have reported running the 13-39 with a short cage derailleur successfully, haven't tried it myself though.

Al
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Old 03-25-06, 11:12 AM   #7
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Quote:
Originally Posted by TJHOO
Given same brand (eg Campy) and level (eg Chorus) of components, does a medium cage rear derailleur (rd) shift as smoothly as a short cage rd?

Any other downsides to switching to med cage?

Am asking b/c am looking for lower gears for climbing (Cat 1 coming up). Curr have 50/34 chainrings and 12-25. Looking at 13-29 which requires med cage rd.

Have campagnolo components.
This would be for Tarmac listed below.

Thx,
There are two issues here, maximum rear sprocket size, and chain wrap capacity.

http://www.branfordbike.com/cgi-loca...95850364#item8

http://www.sheldonbrown.com/gloss_ca-g.html#capacity

You'll be fine on the maximum rear sprocket size. You're already exceeding the rated capacity of your rear derailleur by 2 (29 vs. 27). If you go to the 13-29 cassette you're thinking about, you'd be exceeding it by 5 (32 vs. 27). But as long as you don't cross-chain, you should be fine. I'd recommend getting that cassette and trying it with your drivetrain. If it looks good in all the gear combinations you use, I'd stick with it. Chorus derailleurs ain't cheap.
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Old 03-25-06, 11:28 AM   #8
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Quote:
Originally Posted by TJHOO
Given same brand (eg Campy) and level (eg Chorus) of components, does a medium cage rear derailleur (rd) shift as smoothly as a short cage rd?
I doubt it.

The purpose of the longer derailleur arm is to take up the additional chain slack that's required by using wider gear ranges.

With Shimano, there are distinctly different road and mountain derailleurs. The mountain derailleurs use a different parallelogram to work with larger cassette cogs. I understand that the parallograms of road derailleurs, whether short or long cage, are the same. The parallogram is what follows the angle of the cassette, shifts the gears, and determines how crisp your shifts will be.

Campy is a little different. They specify different large cog capability for different cage lengths, but that changes for the same derailleur depending on whether you are using a double or triple crankset. That leads me to believe that the parallograms for Campy derailleurs, short medium and long, are also the same.

Through the years I've ridden with a variety of short and long cage road and mountain derailleurs. I can't say that I've found any shifting differences that I would attribute to derailleur cage length.
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Old 03-25-06, 11:30 AM   #9
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Thanks for your astute help.

Called LBS. Trusted mechanic there who built up my Tarmac said I could 1st try the 13-29 w/ a new chain. He said I'd obviously want to avoid cross chaining; esp the big/big combo. He said he could leave the chain a little long, to possibly avoid locking up if I went into big/big combo. This would leave some sloppiness in the small/small combo.

He said if could not get this to work on stand or on road, then could get med cage RD.
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Old 03-25-06, 11:33 AM   #10
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LBS mechanic felt that there is room to wiggle w/ Campy.

Quote:
Originally Posted by Retro Grouch
I doubt it.

The purpose of the longer derailleur arm is to take up the additional chain slack that's required by using wider gear ranges.

With Shimano, there are distinctly different road and mountain derailleurs. The mountain derailleurs use a different parallelogram to work with larger cassette cogs. I understand that the parallograms of road derailleurs, whether short or long cage, are the same. The parallogram is what follows the angle of the cassette, shifts the gears, and determines how crisp your shifts will be.

Campy is a little different. They specify different large cog capability for different cage lengths, but that changes for the same derailleur depending on whether you are using a double or triple crankset. That leads me to believe that the parallograms for Campy derailleurs, short medium and long, are also the same.

Through the years I've ridden with a variety of short and long cage road and mountain derailleurs. I can't say that I've found any shifting differences that I would attribute to derailleur cage length.
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