Short vs Medium Cage Rear Derailleur

[jma6610]

I'm planning to get a 2015+ Campy SR mechanical group. I normally would need a low gear of only 36x27, which requires only a short-cage rear derailleur, but am planning to travel to Europe next year and ride mountains so I'm concerned about needing lower gears. The campy short-cage SR is claimed to handle only to a 29 tooth cog set, but the medium cage will go to a 32 tooth. I'm wondering what you could tell me about the decrease in shifting quality I would experience if I moved from the short cage to the medium cage? Is there much difference? I'm currently on a 2014 Campy SR setup (with short cage RD) and want to move that to a secondary bike and get a newer group on my main bike.

Thanks

[alcatraz]

The difference is negligible I think. Because the longer cage derailleurs have similar distance to the snaller cogs as the shorter cage. Especially when you slacken the B-screw it would be nearly the same as a short cage.

I'd say a 32t is good to have for any kind of serious climbing. With today's 11s cassettes having a 32t doesn't sacrifice the high speed gear increments of the higher gears compared to the 11-26t and so on. The tooth difference is larger only on the 4 largest cogs.

/a

[TonyM]

Or go for compact 50/34

[Ettore]

I don't understand the purpose of short cage derailleurs on road bikes anyway. Anyone care to explain?

The way I see it, a medium cage derailleur will lower the friction of the chain, since doesn't have to twist so much. One can imagine that rotating a link requires a tiny bit of force to overcome the friction between two links, and since a short cage RD changes the direction of the chain more than a medium cage RD does, this would mean the short cage RD eats a little more wattage.

[Alexandrumarian]

I have 2015 group, 50-34, short cage, short 405 chainstay which is not the friendliest for Campy. Chain length was set on a 29 cassette. I use a 12-25 for flats and gambled on the new 11-32 Centaur for steep hills. Pretty cheap so no big harm if it wouldn't work. Luckily the cage takes it without bottoming out, and with the B screw loose there is a ton of clearance to upper pulley wheel. Hanger drop is about 24mm (center to center, pivot to axle)
The only problem is the chain rubs on the top of the front derailleur cage making a funny noise, otherwise it seems to be relatively safe if not really usable. So as long as I don't forget myself and shift to the big ring when finishing a hill, all is smooth. The Centaur cassette is a genuine boat anchor at 335 grams, while Potenza should be marginally lighter. At some point I'll save and try the Sram 1190, seen several reports that it works fine with Campy.

[jma6610]

Thanks everyone. This is very helpful, especially Alexandrumarian's comments. I just looked and realised that I also have 405 chainstays, which may explain a few things. ...never measured hanger drop before, but mine looks like it's about 30mm, so that should provide even more clearance. A medium cage wouldn't do anything about the chain rubbing against the top of the FD - perhaps raising it a bit would work? ...and I would think that the medium cage is more about the number of links of slack it can take up when going to the extreme positions (that I avoid anyway) rather than clearance to the large cog?

Sram cog set in 11-32 might be a good option, but I think that Campy also has a newer 11-32. Now that I have a 4 arm 2015+ type crank (just not the rest of the 2015+ group), I do have the option of swapping for compact 50/34 rings which on 34/29 get me almost all of the way, but not completely to the same as a 36/32. Unsure if I need to go all of the way down to 34/32, but I've never ridden in Europe before - I would hope that 34/29 would be low enough - will have to ask a few who have ridden in the area who are about my speed what they do before I decide.

[robertbb]

I've been using Potenza medium cage RD with full Chrous 2015+ groupset on two bikes since the day Potenza was released (actually a week prior, as one of the online stores jumped the gun). In Campy land, Chorus/Record/Super Record didn't get medium cage options until a year after Potenza. I run 50/34 rings on both bikes, and have absolutely no problems running a 12-25, 11-29 (both Chorus) and 11-32 (Potenza) cassette on various wheelsets (Zonda C17, Shamal C17 and Bora Ultra 2017 Diamante). I used to have a chorus short cage RD and I wouldn't be able to tell the difference blind.

I wish Campy would release a Chorus or Record/SR level 11-32 cassette... the Potenza one is a brick (but I still use it for the gearing when I go alpine).

[Alexandrumarian]

I wish Campy would release a Chorus or Record/SR level 11-32 cassette... the Potenza one is a brick (but I still use it for the gearing when I go alpine).

Chorus 12-29 is not much under 300 so would still be a brick unless SR with lots of Ti, yet not even close to Sram which is listed at 196g. My tiny SR 12-25 is 200!



As for front cage rub, I guess it can be reduced by raising the derailleur but I find the shifting is better when it is at 1mm from the teeth. Might be better on 52.

On 405, I have the chain actually rubbing the large ring in small small and a noisy big big even on the 12-25, which doesn't happen on my 415 bike, but we are not supposed to use the extremes...

As for gearing, I believe a 34/32 can be useful even for a light and fit rider when the road often goes over 10%. Look at Froome spinning. For me it made the difference from painful to almost enjoyable. At 95Kg I would often drop under 50 rpm while running out of torque with pain in the knees while the HR stayed too low.

[robertbb]

Yeah I hear ya about the weight. I'd probably spring for an all-Ti SR 11-32, since for me it's an alpine/altitude-only set-up and I will do a handful of those types of "A" rides a year, so wear isn't as much of a factor. Happy with 11-29 or 12-25 for all other regular riding including the smaller climbs near home.

[AJS914]

I've been using Potenza medium cage RD with full Chrous 2015+ groupset on two bikes since the day Potenza was released

Interesting. I thought you couldn't use a Potenza rear derailleur with Chorus/Rec shifters.

[Mr.Gib]

I have a fair amount of experience switching between short and medium cage derailleurs on various bikes and I can conclude that in all cases drive train performance is improved. The longer cage simply manages the chain better which results in better rear shifting and the elimination or reduced likelihood of dropped chains, chain suck, etc. I now use medium cage derailleurs on some of my bikes even though a short cage would still be fine with my gearing.

As for the gears that you need in mountains in Europe, the fact that you need to ask tells me that you absolutely need or would happiest with 34-32. If you are not a gifted climber in very good shape, I can guarantee that if you go with less then 32, at some point in your own private hell on a mountain pass, you will resolve to go to the closest bike shop to get a new derailleur and a cassette with a 32. Look up Tre Cime di Lavaredo, Monte Zoncolan, Mortirolo, etc. and you'll see what I mean. The last thing you want to do is adjust your rides to avoid the steep stuff.

Fact is, even if you are OK with a 28 tooth cog on a 10 or 12% grade, you will find short stretches (and sometimes not so short) that are 15% and even up to 20%. At those gradients everyone, including elite riders, will thankful for a 32 tooth cog.

The Pragelpass in Switzerland is prime example of what to expect, 26 km at 4%. No problem right? Could rip up that in the big ring right? Then you learn that of the 26 km total, about 20 km of it averages between 0 and 2%. You do the math.

[robertbb]

I've been using Potenza medium cage RD with full Chrous 2015+ groupset on two bikes since the day Potenza was released

Interesting. I thought you couldn't use a Potenza rear derailleur with Chorus/Rec shifters.

Something about the spring on the Potenza RD not being as strong/tight as that used on C/R/SR. I can assure you it works flawlessly, however.

[dmtevo]

I’d highly recommend a 34 - 32. I went to Annecy back in September, this was my first experience of the mountains.
It’s not the gradient that’s the struggle it’s the distance and duration. Having the 32 meant you could change things up a little!
My friend did the first day on a 34, 25. He survived the climbs but the next morning we went to a local bike shop and he paid big money for a 32 cassette.
For my 32 Cassette I swapped out the short cage for a medium, my friends just opted for a longer B screw and it seamed to work ok.
Others have used the RoadLink to good effect!

https://www.wolftoothcomponents.com/products/roadlink

[c50jim]

I've been traveling regularly for the last 20+ years and have fiddled around with various Campy gearing mixes. I originally went with 53/39 and 28 or 29 tooth small cog. Don't know how I did it. Tried triples for a while but didn't have much use for the small ring except on the big hills in Europe. Used 50/34 for a long time with 13-29 and later 12-29. I was going to the Pyrenees in 2015 and decided to take the plunge to 11-32. At that time, I had two switch to an Ultegra cassette but it worked OK with Chorus shifters and Athena mid cage derailleur. I can't say the shifting is stellar but it does work. Poor shifting might just be the coupled bike getting disassembled and packed repeatedly and things just going a little off. My mechanic tried the 11-32 cassette with the Chorus short cage derailleur and didn't like it so we went Athena (to match the 2014 shifters). I switched to a Potenza cassette this year. Shifting is about the same but I prefer the Campy gear ratios in the middle. I'm going to swap out the shifters and derailleurs for new Chorus stuff in the spring in the hopes that it will work perfectly again.

During the 10 speed era, I swapped between various close or wide ratio cassettes with a mid cage derailleur and had no problems.

[stormur]

I wish Campy would release a Chorus or Record/SR level 11-32 cassette... the Potenza one is a brick (but I still use it for the gearing when I go alpine).

They did. It's called Sram Red22 11-32 1190 cassette