Short or Long Cage?
 

How do I know if I need a short or a long cage rear derailer? I want to upgrade my mountain bike's rear derailer but I have no idea what whether the Acera derailer on it now is short or long cage and it says nothing on the Shimano website.

Someone correct me, but aren't all MTB rear derailluiers long cage to accomidate the larger rear cogs and the usual triple chainring? I'm fairly certian this is correct. Short cages are usually found on double chainring road groups with a rear cog max of 21/22 teeth.

Your acera derailleur is long cage. Only XT and XTR are made in short cage I believe. Short cage allows snappier shifting....they are used on DH bikes and the like.

So then to replace it I would need a long cage, or could I have a short cage? My cassette goes up to a 30 tooth cog.

i'd get long cage. i think i read somewhere 28t is the highest one should go with a short cage.

Med ,and long cage xtr/xt are all speced for a 34 large cog. Cage length is about wrap capacity.

they are actually refered to as medium cage.

No! There are actually medium cage mtb too. Short cage shimano road are speced for 27 teeth. Cage length is about wrap capacity.Large cog ability is in the parallelogram.

Get a long cage, as that is what you have. Or do the math to see what you can use. Wrap capacity is what cage length is about. (Large chainring teeth - small chainring teeth + ( Large cog teeth - small cog teeth) = the wrap capacity you need. Stay out of the small cogs when in the granny and you can get away with a derailer with less capacity.

Is it really that hard to make one big post instead of 4 posts in a row? About the medium long short or whatever......it depends on what they make in that year.

4 different issues my friend. And as for what you said about the cage lengths, that's just more nonsense like so many other issues in this thread.

What
It was
Different issues....



And nothing I say is nonsense.....how dare you.