bluffskruff

I am trying to find out what is better for the kind of riding I do. I do mainly trails. Not to much down hill. I have a hard tail with front shox so trying to find out what would be better a long or short rear derailleur and what is the difference for.
thx

frankenmike 

The difference is in how much chain you need to wrap, which is determined by: The sum of the differences between the highest and lowest number of teeth on the biggest and smallest chainwheels, front and rear. For example, a crankset with 22t small ring and 44t large ring paired with an 11-34 cassette requires (44-22)+(34-11)=45t wrapping capability. This number should then be matched or exceeded by the number listed on the derailer. In laymens' terms, if you use a triple crankset get a long cage derailer.

jimc101

For MTB's Shimano don't do short cage RD's, only medium (GS) and long (SGS) SRAM give the option of all 3 lengths. As Frankenmike you need to know how many T your cassette & crank are, and buy according to that, if you look at the Shimano Tech Docs, you can see what they spec the RD's for.

bluffskruff

thanx for that info guys, i will be looking more into that when i get home. thx

pablosnazzy

get the derailleur that fits your cassette.

Dannihilator

Calling your bluff. I seem to remember there being a shimano saint SS cage deraillieur, and I've had 8 speed xtr short cages in the past. Unless you are riding a DJ/4S/4X/DH bike, it's better to run the proper deraillieur to your gearing.