I had a similar problem with an old pair of RSX STI levers. A bike shop told me that they would have to be replaced as the ratchet was worn out. Just to make sure I undid the large allen bolt on the front and then a second little screw this reduced the levers to about 20 tiny parts that I didn't stand a chance of putting back together but did confrim that the ratchet was very worn. These things are built by robots in Japan and are not servicable by humans, try to get some more use out of them then replace them when the ratchet refuses to hold at all. I replaced mine with bar end shifters which I like a lot.
James, May 2006
