# Standard to medium cage rear derailleur conversion



## Bnystrom (Oct 27, 2007)

I need to convert a Campy 10 speed rear derailleur from the standard cage to a medium cage in order to use a 13-29 cassette. Is there any problem with doing this? I have Record, Chorus and Centaur rear derailleurs and it doesn't matter which one I convert. 

Are there any good sources for the cage plates?


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## bikerjulio (Jan 19, 2010)

you don't need a medium cage. short cage is fine.

post your front chainrings and I can advise further.


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## roadworthy (Nov 11, 2011)

Have to be a bit careful about bj's comment about not having to change. Yes, many run 29t rear cog size with a short cage. But if you listen to Campy's A-level of functionality...Campy tends to be conservative to cover their you know what...if you run a compact OP with large tooth count difference, chain wrap is marginal with 29t with a short cage. I personally run 29t Campy cassette with 75mm mid cage length.

Also, OP...forget about swapping cages...or I wouldn't. Ebay your derailleurs and buy new from Ribble in the UK...rock bottom prices.

Good luck.


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## bikerjulio (Jan 19, 2010)

In this case I actually know what I'm talking about.

29 less 13 is 16T

if OP has a 53/39 up front, then that's a 14T difference, *and a short cage will handle a 30T wrap, across the whole range with no problems at all.*. 

if OP has a compact, say 50/34 up front then a perfectly workable solution is doable, except that extreme cross chaining from the small chainring will not be doable beyond about the 15 or 14T sprocket. But then you shouldn't do that anyway.

In both cases, it's important to get the chain length right, and also the adjustment to maximise upper pulley clearance from the 29T sprocket (but then you'd have to do that with a medium cage too).


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## roadworthy (Nov 11, 2011)

bikerjulio said:


> In this case I actually know what I'm talking about.
> 
> 29 less 13 is 16T
> 
> ...


In bold. You can look at it that way, but the manufacturer Campagnolo doesn't. They look at protecting for worse case X-chain and so do I and how their spec is published. I would never build a bike that wasn't made to shift well in every gear including all X-chain combinations....with slack chain and tight chain.

OP, my advice is...if you run a 50/34 with 29-13, don't run a short cage. Get a mid cage. This isn't just how I do it but in accordance with Campy's recommendation for a chain wrap of 30T max. I never want to avoid a given X-chain combination briefly in the heat of the battle or bail out situation on the road.

Chain length is always critical, quite right.


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## Bnystrom (Oct 27, 2007)

I'm running a 50/34 compact in front and the standard cage rear derailleur is marginal with a 13-26, so I figure that I will need the medium cage with a 13-29. I agree with you about building bikes to suit the worst-case, cross-chain situations; I won't do it any other way.

One question I have is whether the medium cage's design does anything to increase the clearance between the upper jockey wheel and the largest cassette cog? The standard cage barely clears the 26, so I can't imagine it working with a 29.

As for buying a complete derailleur rather than changing the cage, this is going to be a "special event" cassette that I'll probably only use a couple of times per year. For me, it's worth spending the few minutes it takes to change the cage for the money I'll save.


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## bikerjulio (Jan 19, 2010)

> One question I have is whether the medium cage's design does anything to increase the clearance between the upper jockey wheel and the largest cassette cog?


No...........



> I'm running a 50/34 compact in front and the standard cage rear derailleur is marginal with a 13-26


So the total wrap is currently 16+13=29.

You are doing it wrong if it's marginal.



> As for buying a complete derailleur rather than changing the cage, this is going to be a "special event" cassette that I'll probably only use a couple of times per year. For me, it's worth spending the few minutes it takes to change the cage for the money I'll save.


That's not going to happen. But you seem to be not really here for advice, so just buy yourself a medium cage RD. Or listen.


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## roadworthy (Nov 11, 2011)

Bnystrom said:


> I'm running a 50/34 compact in front and the standard cage rear derailleur is marginal with a 13-26, so I figure that I will need the medium cage with a 13-29. I agree with you about building bikes to suit the worst-case, cross-chain situations; I won't do it any other way.
> 
> One question I have is whether the medium cage's design does anything to increase the clearance between the upper jockey wheel and the largest cassette cog? The standard cage barely clears the 26, so I can't imagine it working with a 29.
> 
> As for buying a complete derailleur rather than changing the cage, this is going to be a "special event" cassette that I'll probably only use a couple of times per year. For me, it's worth spending the few minutes it takes to change the cage for the money I'll save.


Since I run the 29t cog with mid cage Campy derailleur, there is ample room for moving the jockey wheel down with the racked screw adjustment.

This is what I suggest. You mention only needing the 29 tooth cassette for a couple of events a year. Just ride the medium cage length derailleur for all cassette options and ebay your short cage. The industry is moving toward longer cage cassettes anyway to accommodate large cassettes which are more popular now anyway. I will tell you that a mid cage shifts just fine and shifting difference is pretty transparent between mid and short cage.


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## Bnystrom (Oct 27, 2007)

Thanks for a very useful reply, without the cranky, condescending attitude of bikerjulio, who apparently thinks I'm an idiot (I used to be in the bike biz and I know how to set up a bike). 

I guess my resistance to making the switch to medium cage derailleurs may be more rooted in a desire to avoid admitting that they are my future, than anything else. :wink5: I appreciate your advice and insight.


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## roadworthy (Nov 11, 2011)

Bnystrom said:


> Thanks for a very useful reply, without the cranky, condescending attitude of bikerjulio, who apparently thinks I'm an idiot (I used to be in the bike biz and I know how to set up a bike).
> 
> I guess my resistance to making the switch to medium cage derailleurs may be more rooted in a desire to avoid admitting that they are my future, than anything else. :wink5: I appreciate your advice and insight.


I believe the point is, they are in all our future...mid cage length + larger cassette size is becoming more standard fare on higher end bikes sold throughout the world. A stock DA cage length will shift a 28t cassette now and many are going to larger cogs in back notably because more cogs keeps spacing close with a wider gearing range.

This is not unlike how compacts have taken over the market and about time. Most can't sustain 300w's when out riding for twenty minutes and very few can hit 1000w's in a sprint and don't need a std double. 

Honestly when out on the road I could care less what others ride and never even look if I pass them or they pass me.

I do however really appreciate short enough gearing to get up the steep stuff when at mile 80 on a 100 mile ride. Last century I did was with standard gearing and on a couple of climbs late in the ride it was pretty brutal.
Cheers.


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