Bicycle Mechanics - Rear Derailleur Cage Hitting Cog in Low Gear

I have a 13-26 9 speed Campy cassette and Campy 9 speed rear derailleur. When I'm in the 23 cog (the second lowest gear), the teeth of the 26 cog hit the top of the inner cage. It's a short cage rear derailleur which officially should be able to handle a 13-26. I've already got the body tension screw all the way backed out. This is a later generation Campy RD whose "b-tension" screw for moving the top pulley away from the cogs is to turn the screw counter-clockwise.

I posted this in another forum and the best response I got was to shorten the chain. This suggestion worked, but I had to shorten the chain by two links. The result is that I now need to be very careful about accidentally shifting into the big-big combination.

Any other thoughts?

What is the front crankset size? 53/39? I would take the bike to a good LBS mechanic. Something doesn't sound right. I use a short cage on a 13-29 on 3 different bikes (8, 9, and 10spd) and don't have the problem you are describing? Are you sure the hanger isn't bent?

What did you change? How did this come about? New wheels? Cassette?

What you're describing sounds like you have incompatible parts. Maybe I'm just reading it wrong. <shrug>

If you had pics I bet the guys would fix it no problem.

Here are some pics. I bought the frameset used. The drop outs seem straight and there's no indication that it's been bent. The rear derailleur didn't come with the bike but I bought it used. The cassette and chain is mine. I was previously running this cassette and chain on another bike - first with the original short cage 9 spd derailleur and later with a 10 spd medium cage derailleur that I bought when the 9 spd one cracked. No problems.

The only "funky" thing that is happening is that I'm running a Shimano crank - a 53/39. Otherwise, the whole drive train is Campy 9 speed. That includes the shifters, RD, cassette and chain. Other than this problem in the second lowest gear the rest of the gears all shift smoothly.

To me it looks like the B adjust isn't set properly. I know that you discussed that in your original post but that's what it looks like. As Deanster said, you derailleur hanger could be bent. Since it sounds like you're stuck I think it's time to roll it into a shop and let them have a go at it.

It looks to me like you started you adjustment on the wrong end of the cassette. Not sure if that makes any sense. Basically, bottom line, its cable tension. You did your adjustment in reverse. Start tuning from the large cog side with your shifters reset to the beginning postion.
If this doesn't make any sense I apologize. There is aways the LBS.

Good luck.