...for a Shimano 105 "Golden Arrow" RD. I'm looking at http://www.loosescrews.com/index.cgi...id=68605511034 and I just want to clarify: if I need to replace both pulleys, then is the top one the "guide pulley" wheel and the bottom one the "tension pulley" wheel? Can anyone tell me what the difference is between a guide pulley and a tension pulley wheel in terms of the actual structure? Is one actually bigger/smaller than the other? I can't tell from eyeballing it.
Also, before installing, is there any part of the wheel that should be lubed? If so, grease or oil?