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Campagnolo 10s Xenon short cage cassette compatibility

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Campagnolo 10s Xenon short cage cassette compatibility

Old 04-21-18, 12:27 PM
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Campagnolo 10s Xenon short cage cassette compatibility

Hey guys, I have a short cage (5.5cm pulley-pulley) Xenon rear derailleur, with a 12-25 cassette.

I've been wanting to get some lower gears for some climbs - specifically 12-29.

I have a compact crankset - 50/34. So my chain wrap adds up (25-12)+(50-34) =13+16=29 at the moment.

I've researched a bit about chain wrap capacity and maximum sprockets, and I'm not sure what's right, or what works in reality.

The 2007 groupset catalogue (has xenon 10s) says for all groupsets in general:
RECOMMENDED COMBINATIONS
• Double or CT crankset + short cage rear derailleur: all CampagnoloŽ sprocket sets except the 13-29
• Double or CT crankset + medium cage rear derailleur: all CampagnoloŽ sprocket sets*

The 2008 documents has no mention of capacity.

The 2006 catalogue (xenon 9s) says :
The short derailleur cage is for the combination of a double crankset with a sprocket set of up to 13-26.The medium derailleur cage is for the combinations of a double crankset with a sprocket set of up to 13-28 and a triple crankset with a sprocket set of up to 13-26.

The 'modern' 2012 documents say for 10s groupsets in general:
Short cage : (Capacity-32, Max Sprocket-30, Min Sprocket - 11, Chainring Front Difference - 16)
Medium Cage : (Capacity-37, Max Sprocket-30, Min Sprocket - 11, Chainring Front Difference -22)

From the looks of it I have the 2007 or 2008 Xenon groupset. But I have looked online and received information about these 10s RDs with short cages having other capacities such as27 (I'm already exceeding this ), and max sprocket sizes of 26.

A 50-34 and 12-29 will result in a chain wrap of 33.

My fear is that if I size my chain the good old small-small gap-between-chain-and-pulley method do you think the chain won't be able to handle big-big should I accidentally shift into it or if I measure it the big-big method I will have excessive slack on small-small.

In your experience, do you think running a 12-29 with my short cage derailleur will work? I'm probably over-analyzing this but that's the fun in bicycle maintenance right!
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Old 04-21-18, 12:44 PM
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As you know the two issues here are the chain wrap and the guide pulley clearing the large (low gear) cog. The first is rider controlled, as in not using the cross over gears (actually the two outer/inner cogs are to be avoided IMO what with the wide cassette widths and short chain stays that these kinds of ders are usually found on). Still you wand to be able to inadvertently shift into the big/big w/o tearing off your der, and the chain length to accommodate that might mean some chain droop when in the smaller /small combos. The second is somewhat dependent on hanger dimension (different hangers can have an axle to der mount dimension other then what Campy specs and chain length (see the first issue). In an ideal world one usually can push the large cog size a couple of teeth w/o pulley knock, but real life bikes are not in this ideal world.


So the real life answer is maybe. Without trying one doesn't know for sure how these various aspects will play together and what compromises might be needed.


I will say that running a system at it's max capacity (or slightly over) is not what the parts want. Andy
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Old 04-21-18, 12:51 PM
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Only because I had no difference in chainring sizes did I manage to use a 14-34t freewheel* with my short cage Chorus

*yes that was a long time ago...

considering getting a longer cage RD or you need more peer revues to help you choose?





....
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Old 04-21-18, 01:00 PM
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Originally Posted by fietsbob
Only because I had no difference in chainring sizes did I manage to use a 14-34t freewheel* with my short cage Chorus

*yes that was a long time ago...

considering getting a longer cage RD or you need more peer revues to help you choose?
I'm pretty cheap and not willing to replace this derailleur just to support a larger cassette, so I was wondering if it would work anyway. I'm changing chains at the moment so it's a good time to think about changing the gear ratio. If it's not too optimal, I might just forfeit and live with my existing cassette, which is not too worn anyway.

I suppose if they say that all sprockets except 13-29 are supported a 12-27 would be a workable alternative?
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Old 04-21-18, 01:37 PM
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Just getting on a Campagnolo thing is pushing any cheapskates affordability..

30 years ago there was a close out selling of Campagnolo's MTB groups of parts..
I got one from NashBar with a short cage, then, thru the bike-shop's suppliers ordered the long cage parts and substituted those..

check with your favorite bike shop and see what Rabbit they can pull out of a Hat.




...
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Old 04-21-18, 02:01 PM
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Silly me, now that I see that their 13-29 exception would mean a 32 tooth chain wrap with a 50/34 - the same as their stated 32 tooth chain wrap limit in the 2012 document.

So a 33 chain wrap, whilst over, is not too rule-breaking either, especially as these printed limits tend to be on the conservative side.
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Old 04-21-18, 02:22 PM
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So? do it and report the results...
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Old 04-22-18, 07:31 PM
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Originally Posted by Andrew R Stewart
As you know the two issues here are the chain wrap and the guide pulley clearing the large (low gear) cog. The first is rider controlled, as in not using the cross over gears (actually the two outer/inner cogs are to be avoided IMO what with the wide cassette widths and short chain stays that these kinds of ders are usually found on). Still you wand to be able to inadvertently shift into the big/big w/o tearing off your der, and the chain length to accommodate that might mean some chain droop when in the smaller /small combos. The second is somewhat dependent on hanger dimension (different hangers can have an axle to der mount dimension other then what Campy specs and chain length (see the first issue). In an ideal world one usually can push the large cog size a couple of teeth w/o pulley knock, but real life bikes are not in this ideal world.


So the real life answer is maybe. Without trying one doesn't know for sure how these various aspects will play together and what compromises might be needed.


I will say that running a system at it's max capacity (or slightly over) is not what the parts want. Andy
Agree.

As Andrew says, the maximum rear cog capacity and the total capacity aren't really related. Max rear cog is dependent on hanger drop, and also on the angle of the derailleur parallelogram, and pulley cage and knuckle geometry. Total capacity depends almost entirely on cage length. The two tend to coincide because a wider-range cogset will increase the amount of chain needed, and thus more capacity. But there are short cage and long cage derailleurs that can have the same max rear cog, as one of them may be intended for use with double chainrings and the other with triples.

If you were to ask me, I'd say it's more important to choose the derailleur based primarily on the max rear cog you need to accommodate (or vice versa, choose the rear cog and get a derailleur to match,) then make sure that derailleur can also handle the total gearing. There's no harm in having unused total gear capacity. And you can push past total capacity if you are very careful not to cross-chain. Or more specifically, find the limits of your chain length and be careful not to use those combinations. But to push a derailleur past its max rear cog capacity may cause physical contact between the derailleur pulley and cogs, and the derailleur always loses.
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