So I had my bike tuned up this spring and I am running into shifting problems again. It seems that I should be learning how to do some of this stuff myself or throw out a lot of money on tune ups. Can anyone recommend a good book that can help me in this area? As a side question: I had a race this past weekend and noticed a couple of times when I got out of the saddle to accelerate that my chain shifted on the back cassete unexpectedly. What causes that?