I am riding a 1999 Trek 5000 with primarily Ultegra 6503. I have recently replaced my shifter cables. Lately, I've noticed that the chain will down shift heavily and unexpectedly when I put load on the chain (climbing, or getting going from a stop), it will also jump gears when I hit bumps. This occurs almost exclusively when I am in the middle ring. I had to ride all of the cobbled sections of the Paris-Roubaix challenge in the small ring because I just don't have big ring power and the middle ring was causing too many problems. I cannot duplicate these issues when I have the bike on the indoor trainer, it only seems to occur outdoors.

Additionally, I've noticed that frequently I can move the right shift lever and there will be no tension in the lever. Sometimes it will take two or three movements to the left for me to feel that it is catching the cable. When I pull the shifter back into tension, the above mentioned chain jumping is less frequent.

I hope I am describing the issue well and that someone can help shed some light on the issue. Thanks in advance.