OK girls. Any wrenches out there want to tell me what tools I need to buy to change a casette, and how hard it is to do? I have a wheel I bought from Emily on this board (thanks Emily, she is beautiful !) that came with a shimano 105 13-23 casette on it and I want to replace it with an ultegra 12-27 casette. The current wheel on my touring bike has an 11-34 XT casette with an XT rear derailleur, so the bike is already tuned to run with the 11-34 casette. Will I expect to have to adjust the derailleur much when I put on the 12-27? In the future how easy will it be to swap these 2 wheels back and forth? It seems since they are both 9 spd, and the cogs on the 12-27 are within the range of the 11-34 that it should swap easily and not require adjustment. Does what I wanna do make sense. I know the 12-27 will work most of the time, but if I need to carry a heavy load I want to be able to use the 11-34, or if I want to ride it on the trainer without wearing out the nicer tires I may want to swap it.