OK. Last time I wanted to change a cog set, I purchased the tools from my LBS, and in showing me how to use the tools they changed it for me. Today, I did it myslef for the very first time. I think I did it correctly, but here is the problem. The bike is my husband's. He was running a 53/39 in front with a 12/23 casette in back and what looks to be a very short cage rear derailleur (all durace 9). The new casette we ordered is 12/25. First DH replaced his chain before going out of town. By mistake he made it a link shorter than the old chain. The new casette arrived today. It seemd to install smoothly (yey, my first time!), and I got the rear dearailleur adjusted so it would shift nicely (mostly all I fiddled with was the barell adjustor on the tension, or whatever that knob is that lets you make fine adjustments in the tension), but I noticed a problem when in the small front ring and large rear ring. The part of the derailleur that hangs down in back hits the spokes of the wheel. Is this because a 25 tooth cog is too large for a short cage rear derailleur, or because the chain is too short? If its the derailleur, can I even find a 9 spd durace rear derailleur anymore, and if so which one do I need (or maybe easier he could go back to a 12-23 casette, he was OK with it but on a very hilly ride last weekend one of the racer boys commented he'd be better off with a 12-25 and since it was worn and needed replacing he decided to try it. Please help, as I am supposed to have the bike ready for us to go on a ride early saturday, and he is getting back from his trip tomorrow nite.