Mistakenly ordered medium cage 6800 rear der.should i exchange or put on bike

[Kingfisher]

Building up another legend ti and made a mistake ordered medium cage 6800 which arrived today. Going to run plain and simple 50/34 up front and 11-28 rear.
Should I just go ahead an install or swap out for short cage...will there be any differences?

[weisan]

install as per normal.

[Mzilliox]

Building up another legend ti and made a mistake ordered medium cage 6800 which arrived today. Going to run plain and simple 50/34 up front and 11-28 rear.
Should I just go ahead an install or swap out for short cage...will there be any differences?

Id use it, gives you the option of using a 11-32 or bigger cassette in the future. No negative to using it other than a few grams extra weight...

[Luwabra]

agree^ your mistake is now your good fortune.

[ltwtsculler91]

There's no problem running it with an 11-28 and it'll allow you to use an 11-32 in the future if you so desire. Only downside is that you can't go to an 11-25 or an 11-23 if you wanted a tighter cassette.

Given your set up, its basically a decision based on which way you'd see yourself going if you were to change cassettes in the future.

[jemdet]

There's no problem running it with an 11-28 and it'll allow you to use an 11-32 in the future if you so desire. Only downside is that you can't go to an 11-25 or an 11-23 if you wanted a tighter cassette.

Given your set up, its basically a decision based on which way you'd see yourself going if you were to change cassettes in the future.

I have never had any issue using a narrow-range cassette with a long cage rear derailleur, even one that had been shifting a 34t cassette the day before. Same chain and all.

As far as I'm aware, the two factors that are affected by cage length are maximum cog size and chain take-up in smaller gears. If your rear derailleur works in the 21t cog in the middle of a wide-range cassette, it shouldn't have any issue with the 21t cog at the end of your TT cassette.

[Ralph]

Keep the med cage. Technically a 11-28 and 34-50......33 tooth difference (17 + 16) .....needs a med cage. And you can still run a cassette with 32.

Hey....I know you can make a short cage work OK, but for your combo....bet the med cage works better. And you can still run combo's with less teeth difference just fine. The upper pulley is in same position as a short cage. So shifting s/b same.

[dddd]

There is some optimization tuning done with these different derailers as far as how they best track the profile of the cassette.
The springs in the mounting and cage pivots may be of different weight, and perhaps the cage offset between the top pulley and the pivot has also been adjusted. The main body of the two derailers we might presume to be the same, but who knows?
Longer-cage derailers are affected less by changes in chain takeup, as far as how far that the A and B pivots move (rotate) in response.
But shorter-cage derailers have less chain length between the pullies, which might affect the way that lateral chain positioning forces are supported for best shifting response.

Both of these derailers are fully within their limits with the 11-28 and 12-28t 11s cassettes that Shimano offers, and one would presumably have a much easier time finding a trade for a short-cage version down the road if needed.

[jemdet]

There is some optimization tuning done with these different derailers as far as how they best track the profile of the cassette.
The springs in the mounting and cage pivots may be of different weight, and perhaps the cage offset between the top pulley and the pivot has also been adjusted. The main body of the two derailers we might presume to be the same, but who knows?


I was curious about this. Shimano does call out a different "plate axle assembly" for SS and GS models, which includes the main body spring.

There is also a slightly different cable routing for the RD cable fixing bolt between SS and GS models.

So yeah, "who knows" indeed. I can't imagine that a GS model would have any issues shifting a 25t cassette, but I also can't speak from experience with that specific model.

[TBLS]

Made the same ordering mistake - bought medium cage 5800 vs short cage. Absolutely no issues running cassettes with largest cogs 23, 25, 28

Never thought about it after I installed it

Installed on Serotta CIII if that matters

[jumphigher]

I'd keep it as well.

[zmudshark]

If you aren't racing crits with it, keep it.

[TheseGoTo11]

Made the same ordering mistake - bought medium cage 5800 vs short cage. Absolutely no issues running cassettes with largest cogs 23, 25, 28

Never thought about it after I installed it

Installed on Serotta CIII if that matters

+1. I've had no issues running 25 tooth top end cassettes with my mid cage 6800 rear d.

[ltwtsculler91]

+1. I've had no issues running 25 tooth top end cassettes with my mid cage 6800 rear d.

Interesting. I was just going by what Shimano and SRAM recommend on longer cage RDs. Logically I can see why it could work, but who knows why they don't recommend it..

[Ralph]

I think racing guys just don't like the look of a med cage VS short. I use a med cage on all my bikes....lets me run about anything. From 55 mm to 74 mm cage length not much different. No one ever notices it. I do think a long cage is noticeable if looks matter to you. I do notice that 90 mm or longer cage if I'm looking at a bike with a very wide spread of gears.

[dddd]

Well, considering that the 9100 RD is now only available in one longer cage length that goes to 30t, the mid-cage 6800 mech shouldn't look too "fred" on most bikes.
But Shimano is conservative with their recommendations and 6800 is a bit different in ways than 9100. It may come down to the tiny details that I mentioned, and even the shifting speed (toward smaller cogs, presumably) has been mentioned in company literature to be a function of the weight of the cage together with the length of chain that it carries.
Just like similar claims that newer, lighter shift levers improve a bike's steering, really!

[hobbanero]

my only gripe with my medium cage setup is that it does not seem to hold the same chain tension as my short cage. On bumpy roads, I lose the chain off the front big chainring with the medium cage but not the short cage (same road, same bike, same FD setup). Could be just a weak spring in my particular derailleur, because I don't know why they would design it that way.

[Mark McM]

my only gripe with my medium cage setup is that it does not seem to hold the same chain tension as my short cage. On bumpy roads, I lose the chain off the front big chainring with the medium cage but not the short cage (same road, same bike, same FD setup). Could be just a weak spring in my particular derailleur, because I don't know why they would design it that way.

The derailleur cage spring tension may be adjustable. From the Rear Derailleur Overhau (https://www.parktool.com/blog/repair-help/rear-derailleur-overhaul)l instructions on the Park Tool web site:

7. As cage is removed from body, make note of the spring hole in the derailleur cage and body. There are commonly two or more hole choices. New derailleurs are typically assembled with the spring in the hole that allows the most relaxed position of the spring. If more cage tension is desired, the spring end can be installed in the other hole.

[dddd]

It's been my experience that a shorter-cage derailer, as with a "GS" vs. "SGS" cage, does a bit better with controlling chain slap noise on an off-road bike.
But as far as having the chain come off (not while shifting) on a road bike, it sounds like something else must be wrong, such as a bent chainring/tooth, bent chain or poorly setup front derailer.

[DrSpoke]

This has happened to me a lot on my gravel bike. So much so that I try to remember to shift to the big ring when descending. I coast along and then when I try to pedal the chain is off. I switched to Di2 and the problem seemed to go away. But has come back again on the last couple of rides. I'm hoping Shimano makes a gravel RD - basically an Ultegra w/a clutch. But am not holding my breath.


my only gripe with my medium cage setup is that it does not seem to hold the same chain tension as my short cage. On bumpy roads, I lose the chain off the front big chainring with the medium cage but not the short cage (same road, same bike, same FD setup). Could be just a weak spring in my particular derailleur, because I don't know why they would design it that way.