I recently purchased this type of RD http://www.amazon.com/Shimano-RD-TX5...STABD824GH5793 as a replacement for my old one. However, I am unable to attack it to the derailleur hanger on my MTB. The hanger is a non replaceable steel one. Am I suppose to slide the RD onto the rear skewer? What is the tiny bolt in the pic used for? It is not long enough to pass through the width of the RD and the hanger.
Any tip will be very appreciated.