Long Cage vs Short Cage Derailleur?
05-06-09, 09:38 AM
#1
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Long Cage vs Short Cage Derailleur?
I am building a new bike and I am using a 39/50 double crank and I want to use a 11-28 sram cassette and a Shimano America Ultegra SL RD-6600-G Rear shorter cage Derailleur. Benefits of a shorter cage length from what I have been able to find :
- Snappier shifts
- better chain tension
- less chain slap / greatly decreased drive train noise (!)
- Better obstruction clearance / improved spoke clearance.
- Slight weight loss -- but you gotta be a real weight weenie to appreciate this one.
The problem is, I read in some areas that this short cage derailleur biggest gear support is a 29T and then I read that the biggest is a 27T. Im getting mixed info on this.
My question is, have anyone of you guys used a cassette with a 28T gear on it with a short cage Shimano derailleur? If so, any shifting problems on the 28T?
Thanks in advance !
- Snappier shifts
- better chain tension
- less chain slap / greatly decreased drive train noise (!)
- Better obstruction clearance / improved spoke clearance.
- Slight weight loss -- but you gotta be a real weight weenie to appreciate this one.
The problem is, I read in some areas that this short cage derailleur biggest gear support is a 29T and then I read that the biggest is a 27T. Im getting mixed info on this.
My question is, have anyone of you guys used a cassette with a 28T gear on it with a short cage Shimano derailleur? If so, any shifting problems on the 28T?
Thanks in advance !
05-06-09, 09:48 AM
#2
Genetics have failed me
You need to look up what the capacity is of the rear derailleur.
And use that formula to calculate the actual capacity you need:
(biggest chainring - smallest chainring) + (biggest sprocket - smallest sprocket)
EDIT: Oh, and of course maximum cog size as directed by the manufacturer should be followed.
And use that formula to calculate the actual capacity you need:
(biggest chainring - smallest chainring) + (biggest sprocket - smallest sprocket)
EDIT: Oh, and of course maximum cog size as directed by the manufacturer should be followed.
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05-06-09, 09:53 AM
#3
Genetics have failed me
Max sprocket size for the 6600 Ultegra short cage and long cage is 27T btw.
The 7900 Dura Ace RD can take a a 28T sprocket.
The 7900 Dura Ace RD can take a a 28T sprocket.
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05-06-09, 09:56 AM
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^ Yep. Both short and long cage road derailleurs from Shimano have a max cog of 27. It's the chainwrap capacity that's different. I run a 28 on mine with no problems, and no people running even larger cogs, but it depends on where your frame's derailleur hanger is placed.
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05-06-09, 09:57 AM
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"The 7900 Dura Ace RD can take a a 28T sprocket."
Maybe this is the deraillure I need to be looking at instead of the ultegra. Thanks for the info Scummer
Maybe this is the deraillure I need to be looking at instead of the ultegra. Thanks for the info Scummer
05-06-09, 09:59 AM
#6
Senior Member
While Shimano states that 27T is the largest cog that almost all of their road derailleurs support, many people have found that a 28T cog works without any problems. Just make sure to adjust the B-tension screw so that the derailleur clears the cassette!
05-06-09, 12:56 PM
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I just switched to an 11-28 and use it with my DA 7800 short-cager. Works fine.
05-06-09, 05:04 PM
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I have an 11-28 with a Tiagra long cage and a 22 tooth front difference. That's a total capacity of 39 and it's rated for 37.
05-06-09, 05:10 PM
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the ratings are conservative to keep idiots from suing the manufacturers.
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Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
05-06-09, 05:30 PM
#12
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None of the advantages of the short cage is accurate other than the few grams of weight.
That said, I can't imagine a RD that will clear a 27 but not a 28. Worst case, you might need a longer B screw. Just be sure to set the chain length properly. In the 50/11 or 50/12, make the chain as long as possible without hanging loose or rubbing the RD cage. If it won't wrap the 50/28, you've exceeded the RD's maximum wrap capacity. If you are sure you will never accidentally shift to that combo, that's no problem.
What many people do not realize is that chainstay length affects wrap capacity. Some frames get up to 2T of additional wrap by having the perfect chainstay length. Manufacturers know this, so some users will get 31T of wrap fro a RD rated at 29 and others won't. The ratings can't assume perfect chainstay length.
That said, I can't imagine a RD that will clear a 27 but not a 28. Worst case, you might need a longer B screw. Just be sure to set the chain length properly. In the 50/11 or 50/12, make the chain as long as possible without hanging loose or rubbing the RD cage. If it won't wrap the 50/28, you've exceeded the RD's maximum wrap capacity. If you are sure you will never accidentally shift to that combo, that's no problem.
What many people do not realize is that chainstay length affects wrap capacity. Some frames get up to 2T of additional wrap by having the perfect chainstay length. Manufacturers know this, so some users will get 31T of wrap fro a RD rated at 29 and others won't. The ratings can't assume perfect chainstay length.
