[QUOTE=afryska]Thanks all for the info. Actually, I was looking closely at the group today, and am a bit confused... it's obviously an integrated and indexed system (not down-tube shifters), but all the components are labeled S.I.S. (including the integrated shifter/break levers). This seems to contradict what everyone said about S.I.S. being only down-tube and bar-end, since these are definately integrated. Could these perhaps be Shimano's first attempts at integrated systems, before S.T.I.?
QUOTE]
You are correct, the sis is on the sti. In fact after I posted my reply to you I realized that I have my sti on the sis (index).
In other words the index "clicks" into each gear as you shift, where friction slides into each gear.
idex somewhat locks into each gear with each "click" as where friction when you shift gears you could over shift or under shift and you may not have your chain alligned correctly.
This is not a problem as you will hear the chain making a noise, and all you have to do is bump your shifter one way or the other.
SIS "index" is just easier and alligns the chain in the proper place as you shift.
again if I am incorrect I am sure I will be corrected, but this is how I understand the sis to work, its how its was explained to me a long time ago from my lbs when I got my first roadie.
Hope that clarifies this question for you.
about weight I dont have a clue, sorry...