The only cramps I will occasionally get on the bike are in the backs of my calves. I normally only get those early in the season when I'm doing a fairly high cadence.

My biggest problems with cramping come post ride, one or two or five hours later. Sometimes I turn over in bed, or when getting up out of a chair, my big muscles will just lock up tight. Verrry painful. The worst is if I have a long drive home from a century or so and I cramp up while driving. You have a limited scope in the car to stretch things out, so you just have to ride it out. Ouch!