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PostPosted: Sun Apr 20, 2014 5:42 am 
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Posts: 361
Manatee wrote:
I put a 6800 GS cage on a 9070 RD and it works great with the 11-32.


did you run it with the short cage first then go to gs for this comparison... my LBS offered to sell me just the GS cage if I wanted to put on my 9070, but I'm sort of half tempted to run the 28T first.. just to know how it feels then maybe get the gs cage later.

28T/32T.. think one chain would get that done ? I kinda have my doubts.


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PostPosted: Sun Apr 20, 2014 4:42 pm 
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I think the only difference will be idiot proof shifting (with 11-32) if you put the GS cage on.
With a short cage you must be careful enough not to go big-big, with a GS you don't have to worry about that.


spdntrxi wrote:
Manatee wrote:
I put a 6800 GS cage on a 9070 RD and it works great with the 11-32.


did you run it with the short cage first then go to gs for this comparison... my LBS offered to sell me just the GS cage if I wanted to put on my 9070, but I'm sort of half tempted to run the 28T first.. just to know how it feels then maybe get the gs cage later.

28T/32T.. think one chain would get that done ? I kinda have my doubts.


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Posted: Sun Apr 20, 2014 4:42 pm 


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PostPosted: Sun Apr 20, 2014 8:05 pm 
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boots2000 wrote:
I think the only difference will be idiot proof shifting (with 11-32) if you put the GS cage on.
With a short cage you must be careful enough not to go big-big, with a GS you don't have to worry about that.


spdntrxi wrote:
Manatee wrote:
I put a 6800 GS cage on a 9070 RD and it works great with the 11-32.


did you run it with the short cage first then go to gs for this comparison... my LBS offered to sell me just the GS cage if I wanted to put on my 9070, but I'm sort of half tempted to run the 28T first.. just to know how it feels then maybe get the gs cage later.

28T/32T.. think one chain would get that done ? I kinda have my doubts.


maybe they are the same... don't know but would it be better to use the 6800 or 6870 GS cage ? on the 9070


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PostPosted: Sun Apr 20, 2014 11:22 pm 
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boots2000 wrote:
I think the only difference will be idiot proof shifting (with 11-32) if you put the GS cage on.
With a short cage you must be careful enough not to go big-big, with a GS you don't have to worry about that.


What? Apparently some folks do not understand what the cage length on a derailleur does. The cage length, short or long, merely wraps up excess chain so it does not hang down under the chainstays when in the small-small combination. It is the CHAIN LENGTH and how the derailleur shifts that determines whether you can use the big-big combination. 50 chainring and 32 cog in this case. The chain has to be long enough to go around both big ring-big cog without yanking the derailleur off the post. Just in case by accident you shift into the big-big combination. You're not supposed to use big-big, but just in case. And the derailleur itself has to be able to get its upper pulley underneath the 32 cog. Some rear derailleurs are built so they can only get the upper pulley so low under the big cog. Derailleur design. You have no control over this. When in the 34 ring and 32 cog, the chain will be fairly tight so both short or long cages will wrap up plenty of chain and keep the chain taut under the chainstay. Shifting the rear derailleur to the 32 cog is 100% INDEPENDENT of what cage length is on the derailleur. Irrelevant!


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PostPosted: Mon Apr 21, 2014 4:15 am 
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There are some minute differences in the geometry of a GS cage versus the normal one. Its not just the length alone.

Its these geometric differences that determine if a cage is suitable for bigger cassettes. Chain wrap is a requirement no doubt, but its not as simple as that.


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PostPosted: Mon Apr 21, 2014 6:48 pm 
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Joined: Tue Nov 11, 2003 9:47 pm
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Location: Santa Cruz, California, USA
For 6800 the SS derailleur's listed max cog is 28t and the GS is 32t.

This chart below shows the same for the 9000GS:

http://www.celebrazio.net/bicycling/shi ... p_2014.pdf


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PostPosted: Mon Apr 21, 2014 10:13 pm 
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The longer cage take up more chain- so you can have a little tension in small/small and not be out of chain when in big-big.
Small point but it makes a difference if you are not a careful shifter.
I ran an 11-32 with my short cage 9000 this weekend. Works fine but I personally would not shift to the 32 when in the big ring. It makes it on the stand- I see nothing but trouble on the road.
Unless maybe you ran another link of chain. Then it would be sloppy in 11 cog on small ring- maybe even 12 cog.

RussellS wrote:
boots2000 wrote:
I think the only difference will be idiot proof shifting (with 11-32) if you put the GS cage on.
With a short cage you must be careful enough not to go big-big, with a GS you don't have to worry about that.


What? Apparently some folks do not understand what the cage length on a derailleur does. The cage length, short or long, merely wraps up excess chain so it does not hang down under the chainstays when in the small-small combination. It is the CHAIN LENGTH and how the derailleur shifts that determines whether you can use the big-big combination. 50 chainring and 32 cog in this case. The chain has to be long enough to go around both big ring-big cog without yanking the derailleur off the post. Just in case by accident you shift into the big-big combination. You're not supposed to use big-big, but just in case. And the derailleur itself has to be able to get its upper pulley underneath the 32 cog. Some rear derailleurs are built so they can only get the upper pulley so low under the big cog. Derailleur design. You have no control over this. When in the 34 ring and 32 cog, the chain will be fairly tight so both short or long cages will wrap up plenty of chain and keep the chain taut under the chainstay. Shifting the rear derailleur to the 32 cog is 100% INDEPENDENT of what cage length is on the derailleur. Irrelevant!


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PostPosted: Tue Apr 22, 2014 1:52 am 
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There is no reason the RD would not work with the 30 or 32T cog, the important is the chainring combination. As long as you do not use the largest cog with the largest chainring, you should be fine with the short cage RD.


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PostPosted: Wed Apr 23, 2014 12:28 pm 
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upside wrote:
I have a 9000 52X36 and use that with the 6800 11X32 with the short cage derailleur and have no issues. Perfect combo for me in the hills, as I am getting a bit old.


Contador uses 34x32 often in races. Team Sky have XC cassettes in stock at their service course.

Not sure your age has anything to do with it. Unless you are implying you were fitter than the world's best climbers when you were their age. ;)

One must ride whatever gears it takes to maintain a cadence of 80+rpm if producing sufficient power is their goal.

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PostPosted: Thu Aug 14, 2014 5:02 pm 
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I am sure this has been answered but have struggled to see a comprehensive answer anywhere on the internet.

If a run a DA9000 rear mech with an Ultegra 11-32 Cassette it will fit but the issue will be either (i) not enough chain to shift into big/big i.e. 50/32 or (ii) too much chain when in small/small i.e. 34 / 11?

If that is the case why would anyone have too little chain? Aren't you far more likely to run 50/32 than 34/11 so it would make sense to have a sloppy chain when you are on small/small?

Thanks


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PostPosted: Thu Aug 14, 2014 7:30 pm 
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There are two issues:

1) will the upper pulley clear the cassette? this can be worked around by using a longer derailleur hanger, or b-screw. Or by threading the b-screw in from the other side.

2) chain wrap capacity. This is the maximum amount of range of teeth your derailleur can handle by wrapping the chain around itself. ie: difference in front chainrings plus difference in rear. so on a 11-32 w/ 39-53 front, you get 21 + 14T for 35T capacity. A compact is 21+16T for 37T capacity. A RD-9070/9000 or 6870/6800 SS (short cage) has a capacity of 33T. The RD-6870/6800 GS (medium cage) has a max capacity of 37T. You can retrofit ultegra medium cages (even the non-di2) to the RD-9070 if you want.

To answer your question, having too little chain would be a bad idea, as the chain would bind trying to make it to big/big, likely damaging your derailleur. Too much chain for the derailleur capacity results in slow shifting, and larger amounts of chain slap. You can get away with using a lower capacity derailleur in many cases, but performance does suffer.


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PostPosted: Thu Aug 14, 2014 7:50 pm 
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Ah so the easiest way to solve this is to put an ultegra RD on the bike.

Any chance shimano release a long cafe version of the DA RD?


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PostPosted: Thu Aug 14, 2014 9:47 pm 
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I wouldn't expect that until after you see a CS-9000 11-32 cassette ;), which I doubt would happen given the CS-9000 uses a carbon carrier, and a 32T would put more leverage on the carrier, which is rumored to be having cracking issues already...

Additionally, the XTR Shimano Rd-9050 will work in this case as well, and handle even larger cassettes / capacity as it comes in a GS and SGS version (long cage).


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PostPosted: Thu Aug 14, 2014 10:03 pm 
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The last two cogs on the 9000 cassettes are riveted to a alu. carrier, therefore the carbon carrier issue would not affect a hypothetical 11-32 cassette.

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Posted: Thu Aug 14, 2014 10:03 pm 


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PostPosted: Thu Aug 14, 2014 10:08 pm 
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ah, I haven't played with one. My bad.

Still see it as very unlikely they'd make a medium cage RD-9000/9070 if they didn't make one originally.


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