vinnydelnegro

I'm looking to purchase an entire group, but am a bit confused about rear deraillers. I'm going to be running a 3 x 9, so I want to make sure that the rear derailleur is compatible with a triple. Currently, I'm negotiating with someone for a group that includes a Shimano 105 rd-5501 rear derailleur. I know that I should be looking for a "long cage" and a model that ends in GS rather than SS. However, I don't know if the seller knows the exact model and I have only seen blurry pictures. From what I can tell, the "tensioner" (sorry if my terminology is incorrect) should be longer on a triple. However, is there a way I can tell by looking at the derailleur itself. Is there a model number somewhere on it that would indicate that it is a triple? Thanks again guys. Your help is always appreciated.

stickydpaul

5501 is a triple, 5500 is a double, so you should be just fine.

vinnydelnegro

oh....cool. i guess i got confused when my google search turned this up. it seems to indicate that the 5501 is a double. of course the picture is of a black derailleur and the description is for a silver.

https://www.icyclesusa.com/catalog/sh...derailleur.htm

is it possible to run a short cage with a triple? Sheldon Brown suggests that there is much more flexibility with rear derailleurs than the manufacturers suggest, but doesn't specifically say that you can run a short cage for a triple crankset. Just out of curiosity.....

Jed19

is it possible to run a short cage with a triple? Sheldon Brown suggests that there is much more flexibility with rear derailleurs than the manufacturers suggest, but doesn't specifically say that you can run a short cage for a triple crankset. Just out of curiosity.....[/QUOTE]

No. Short cage derailleurs do not have the capacity to absorb the "chain wrap" that is required.

Regards,

Tom2slow

so let me get this straight (butting in here)
If I want to change a bike that has a double to triple I am likely to need:
chain (duh)
the new triple
ft der
and a rear der?

I understand my mileage may vary and circumstances may be different.....but as a rule?

Gonzo Bob

Depends on how much chain you need to wrap, how precise you are about setting the chain length, and how careful you are about not using the big-big and small-small combos. If you run something like a 12-21 with a 52x42x30 which "requires" a rear derailer with a capacity of (52-30)+(21-12)=31, you could get by with a Shimano short cage which has an advertized capacity of 29. I once set up my road bike with a 13-30 and 50x34. Technically this requires a rear derailer with a capacity of 33 but I used a short cage Shimano with a capacity of 29 and everything worked fine even in big-big and small-small.

fmw

You can use a short cage with a triple. However, when you are using the smaller cogs on front and rear, the derailleur arm may not take up all the slack in the chain and it will sag. A little sag isn't likely to hurt things. You can always stay away from those gearing combinations (and probably should anyway) to avoid the sag. A longer armed derailleur is better, of course.

Retro Grouch 

No. Short cage derailleurs do not have the capacity to absorb the "chain wrap" that is required.[/QUOTE]

I'm going to disagree, at least to a point.

Generally with a triple crankset, particularly on a road bike, you only use the granny chainring with the two or three largest rear cogs. Since you never get into the little/little combination, you don't really need enough chainwrap to handle it.

The opposite, however isn't true. While most riders avoid using the big/big combination, you still need enough chain length to safely cover that combination. If you ever accidentally shift into that gear, even for just a second, a too short chain can cause a LOT of damage.

That said, if you want your bike to look "factory" insted of like something you cobbled together in your garage, you will need a long cage derailleur with a triple crankset.

SaddleBags

What about the opposite - running a long cage on a double? I've got extra spare parts and putting together another build.
Drivetrain is 6600 with maybe a Compact (50/34) crank.