jpsawyer

Hey.
So I have a broken long cage Shimano Ultegra 6700 rear derailleur (the arm with the barrel adjuster broke off), and a Shimano 105 5700 short cage rear derailleur in my parts bin. The Ultegra one replaced it a few years ago.
Both derailleurs are in great shape, minus the broken barrel adjuster arm. And finding long cage 10 speed derailleurs is hard now.
Has anyone here ever replaced just the cage? Will there be compatibility issues?
I'm assuming its doable, but wanted to ask here before getting into it and then having two useless derailleurs.
Thanks!

Andrew R Stewart 

Since the service of cage replacement went away a few decades ago for all practical purposes your question will likely require finding someone who has tried this on these exact two ders before. Shimano has used a variety of different cage pivot/attachment designs over the years, usually a design is used over a range of models until some reason makes them change.

The thing had to be able to be assembled so it has a way to come apart. One thing that I have seen with Shimano cage pivots is they have a pin/screw that retains the cage pivot bolt within the body's housing. This screw/pin has been "locked" in place with a rivet like deformation, of the hole in the body, bearing on the pin/screw's head. So even if its a screw you will have to unthread it through the rivet like notching before it will come loose from the body.

Once the cage/pivot bolt can be pulled somewhat out of the body's housing then the cage can unwind (due to the spring's tension) and often be simply pulled out entirely. Since the Ultegra der is already a toss out (except for pulleys, anchor bolt and limit screws for the most part) I suggest you explore taking it apart first. Then if you gain knowledge and/or confidence try the 105. Andy

Dave Mayer

I've disassembled and mixed/matched dozens of Shimano rear derailleurs. Not this exact combo, but if it works, then it works. It should take less than 10 minutes for the cage replacement.

Unscrew the long fixing bolt on both derailleurs - do not strip the tiny hex heads! Reassemble with a liberal amount of grease.

fietsbob

Yea with Shimano, Its parts cannibalization from a donor derailleur....


I only did so on old Campag Euclid, their discontinued run at the MTB market,

as said above, this was 30 years ago..


*as sung by Edith Bunker on All in the Family..

Dave Mayer

So I looked at the exploded parts diagram of Shimano 5800 and 6800 rear derailleurs. They are incompatible designs. Previously, 105 and Ultegra rear derailleurs had compatible lower assemblies. No longer.

105 may be compatible with Tiagra and lower.

Matt Gaunt

Just in case you decide not to try the cage exchange with your 5700 mech (or it doesn't work), it looks like you can still pick up new 5700 105 GS cage rear mechs on Wiggle and Chain Reaction (and probably other sources). Don't be put off by the "medium cage" label. The GS cage is the 'long cage' for road (SS being 'short cage' for road and SGS being actual long cage for MTB).

masi61