As you find yourself changing the number of
chain rings that you use from three to two, or from three to one, or two to one, you’ll
find that you may be able to also get away with changing the length of your derailleur
cage. Most bikes come with a long cage, which is designed to take up a greater difference
in front chain rings. The smaller the difference that you have, the shorter length you can
get away with. So, this is a long derailleur cage. This derailleur here is medium length.
You can see that it’s a little bit shorter. And then, this cage here, is a short cage,
which is once again shorter yet. So, medium cage derailleurs are good if you’re not running
an extremely large gear range in the rear as well, and you’re running three cages, so
that would be the medium cage one. The long cage is good if you’re running three rings
up front, and a wide range cassette in the back, like an eleven or twelve-thirty-four.
The small, short cage derailleur, which originally, these were only on road bikes and now a few
companies make them for mountain bikes specific use, is really good for a double-ring application
with a tight rear cassette, or a single-ring application because the shorter the cage,
the shorter you can make your chain and the less swing weight there is, so the snappier
and more effective the shifts are. Another reason to change your rear derailleur is obviously,
if like this one, things are broken. So, when we’re changing out our rear derailleurs we
want to make sure that we set out limit screws correctly, and that we’re setting cable tension
the right way. You can follow some of those steps other places, but basically you want
to make sure that you’re aware if you have a Shimano style derailleur with a rear loop
and a different cable pull, because one type of shifter works with one type of derailleur.
So, yeah, don’t be afraid to change out you’re derailleurs to save some weight and increase
some performance, or just to suit your needs better.