Short vs Medium Cage Rear Derailleur

Discuss light weight issues concerning road bikes & parts.
robertbb
Posts: 202
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

stormur wrote:
robertbb wrote: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 :mrgreen:


... that works on a Campy freehub?
It's ALL about the bike.

stormur
Posts: 1156
Joined: Tue Aug 12, 2014 3:50 pm
Location: FIN

by stormur

Nope :)

How Potenza -32 cassette is build : largest cogs : block of 2/3 ? Did you check is it possible to mix just largest sprockets with f.e. rest from Chorus cassette ?
Go to Heaven for the climate, Hell for the company.
Mark Twain


I can be wrong, and have plenty of examples for that ;)

by Weenie


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Rick
Posts: 2001
Joined: Sat Aug 29, 2009 4:30 pm

by Rick

Ettore wrote:I don't understand the purpose of short cage derailleurs on road bikes anyway. Anyone care to explain?
My experience seems to follow the theory: a shorter cage results in slightly faster and more reliable shifts. But as a practical matter, it is a very small difference In fact, on one of my road bikes I am using a long cage mtn bike derrailleur just so I can also use a 34 tooth and a triple crank. No question that comparing the two extremes a short cage is crisper than a long cage. So it is a compromise based on what you really feel you need. If I were a crit specialist I would have a sort cage on that bike (and a tight cluster). For general road riding it is such a small difference that just going with whatever is recommended will probably make no noticeable difference. Accurate alignment and setup makes a lot bigger difference than cage length.

With your specific story, I would go with the longer cage and not worry about it.

alcatraz
Posts: 558
Joined: Mon Aug 29, 2016 11:19 am

by alcatraz

If you have a large cassette you probably get better shifts with a medium cage derailleur. (A short cage usually needs its B-screw adjusted almost to the max for larger cassettes and thus you get too high chain tension.)

If you run 23-26t cassettes you are probably better off running a short cage derailleur. The upper pulley will stay closer to the cogs and ensure better shifting.

/a

Mr.Gib
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by Mr.Gib

Rick wrote: My experience seems to follow the theory: a shorter cage results in slightly faster and more reliable shifts.
I disagree with this. The quality of shifting will depend on the relationship between the upper jockey wheel and the cassette. To my knowledge this does not change between short and longer cages. In fact a longer cage allows you to set the upper jockey wheel closer to the cassette without ending up with a loose chain in the 11 tooth cog. This will improve shifting on 11-28 cassettes (and perhaps 11-27 - haven't tested this one).
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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Rick
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Joined: Sat Aug 29, 2009 4:30 pm

by Rick

Mr.Gib wrote:
Rick wrote: My experience seems to follow the theory: a shorter cage results in slightly faster and more reliable shifts.
I disagree with this. The quality of shifting will depend on the relationship between the upper jockey wheel and the cassette. To my knowledge this does not change between short and longer cages. In fact a longer cage allows you to set the upper jockey wheel closer to the cassette without ending up with a loose chain in the 11 tooth cog. This will improve shifting on 11-28 cassettes (and perhaps 11-27 - haven't tested this one).
A shorter cage is simply stiffer (laterally) which gives the crisper, more precise shifting. . Even if the distance to the jockey wheel remains the same. The looseness of the chain is is a separate issue and should be adjusted so that it is NOT too loose on the smallest cog. I have tested this, with all the way from short-cage+corncob cluster to the wide range triple I cited above. I just happen to have numerous bikes (because I am old ?) But they all work adequately well, assuming careful setup and alignment.

Mr.Gib
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by Mr.Gib

Rick wrote:
Mr.Gib wrote:
Rick wrote: My experience seems to follow the theory: a shorter cage results in slightly faster and more reliable shifts.
I disagree with this. The quality of shifting will depend on the relationship between the upper jockey wheel and the cassette. To my knowledge this does not change between short and longer cages. In fact a longer cage allows you to set the upper jockey wheel closer to the cassette without ending up with a loose chain in the 11 tooth cog. This will improve shifting on 11-28 cassettes (and perhaps 11-27 - haven't tested this one).
A shorter cage is simply stiffer (laterally) which gives the crisper, more precise shifting. . Even if the distance to the jockey wheel remains the same. The looseness of the chain is is a separate issue and should be adjusted so that it is NOT too loose on the smallest cog. I have tested this, with all the way from short-cage+corncob cluster to the wide range triple I cited above. I just happen to have numerous bikes (because I am old ?) But they all work adequately well, assuming careful setup and alignment.
Ah, but this suggests that the cage on a longer cage derailleur is not stiff enough. Fact is the cage simply does not experience torsional forces that would result in deformation. The stiffness element that would affect shifting is the connection between the upper jockey wheel and the body of the derailleur and this should be the same regardless of cage length.

The issue regarding b-screw adjustment is simply that the further away the upper jockey wheel is from the cogs, the less precise the shift tends to be due to lateral play in the chain (which increases with chain wear). With Sram, setting the chain length to safely handle the big-big combination (50-28) results in a loose chain on the 11. Of course the simple solution is the adjust the b-screw to take up the slack. When this is done the upper jockey wheel is now too far away from the cassette to give optimal shifting, a problem that is solved by a longer cages' ability to take up more chain slack.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

joeyb1000
Posts: 96
Joined: Thu Mar 03, 2016 8:37 pm

by joeyb1000

Will post text later

ooo
Posts: 443
Joined: Sat May 21, 2016 12:59 pm

by ooo

GS and SS version of the same Shimano rear derailleur may have different body geomtery:

RD-6870-SS - rollers and chain are closer to sprockets on smaller ratio cassettes
RD-6870-GS - rollers and chain are closer to sprockets on wide ratio cassettes, plus extra capacity & extra chain slack
RD-6870-GS with cage replaced to SS - may be better option for 1x11 setup

http://handsonbike.blogspot.co.id/2017/ ... a-di2.html
Attachments
RD6870 Short vs Mid Cage Comparison.JPG
'

joeyb1000
Posts: 96
Joined: Thu Mar 03, 2016 8:37 pm

by joeyb1000

Just switched Campy to medium cage (and 11-32):
1. The short cage can handle the 32 (including my EPS derailleurs), the issue is the large chainring and the 2nd cog. On the short cage, the chain is stretched to the limit.
2. I see no change in shift quality on any cassette.
3. The medium cage says it's for 29 or 32 cassettes only, but I have no problems on smaller cassettes.
4. I think the medium cage is quieter, but that's probably due to the new chain.
5. Campy's Potenza-grade cassette is slightly noisier than Chorus+ cassettes. It has a more metallic sound to it.
6. The new derailleur is the HO version. I can't see any difference


I'll post photos when I figure out how.

OHYONGUN
Posts: 10
Joined: Thu Dec 21, 2017 2:10 am

by OHYONGUN

Red 22 mechanical is not yet wifli. We have two table rings. I'd like to get 34T support.

robertbb
Posts: 202
Joined: Thu Jul 23, 2009 3:35 am
Location: Melbourne, Australia

by robertbb

@ joeyb1000:

Just switched Campy to medium cage (and 11-32):
1. The short cage can handle the 32 (including my EPS derailleurs), the issue is the large chainring and the 2nd cog. On the short cage, the chain is stretched to the limit.

With what sized outer chainring?

2. I see no change in shift quality on any cassette.

Seconded.

3. The medium cage says it's for 29 or 32 cassettes only, but I have no problems on smaller cassettes.

Seconded; I've happily run an 11-25.

4. I think the medium cage is quieter, but that's probably due to the new chain.

Definitely quieter.

5. Campy's Potenza-grade cassette is slightly noisier than Chorus+ cassettes. It has a more metallic sound to it.

And also a boatload heavier.

6. The new derailleur is the HO version. I can't see any difference

Interested to know how this compares in design/shape to the Potenza Medium Cage derailleur.
It's ALL about the bike.

joeyb1000
Posts: 96
Joined: Thu Mar 03, 2016 8:37 pm

by joeyb1000

1. 52/36
5. You don’t notice when riding on the road.

dmp
Posts: 321
Joined: Fri May 08, 2009 8:31 pm
Location: Denver

by dmp

Joey, you note the chain seems short when on the big chainring and the 2nd cog- does this imply the large chainring and 1st cog are unusable?
Any idea what the 11-32 would be like with a compact (50/34)? Would this problem be lessened?

I'm riding on 2014 SR (short cage, they didn't have a medium one then), with a compact and 12-29 cassette. This has been ok for me here in Colorado where we don't have too many climbs over 10% (they are certainly long, but not as steep), but riding in Israel this fall there were plenty of grades over 10%, with short stretches of over 15, and some particularly brutal switchbacks of 20+. I would have loved a 32 on the back, and would think about getting one for my next trip there if it all work with my current drivetrain.

TobinHatesYou
Posts: 601
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

Why would the derailleur be pulled to capacity on the #2 cog and not the #1? He must be saying 1-1 works but 2-1 doesn't and 2-2 barely has any slack.

by Weenie


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