Been lurking for a few months. I bought my 640 last spring when I was recovering from pneumonia and the doc told me could not engage in my normal leisure activities, climbing and mtn biking. I didn't really know what I was buying and was mostly planning to use it as a daily ride to work. Then I took it off road in the national forest by my house. Now I'm in deep and can't get enough of exploring fire roads and single track around Santa Fe on this beast. I'm in the midst of disassembling the bike and taking care of any issues I find. Many thanks to all who have contributed technical info on the 640!