I'm 6'4" 275 and I get all my miles riding my road bike for commuting 11 miles each way 1-4 days per week. In the peak of my commuting season, which is starting this week due to the mild winter, I will drop down to 255 or so. I'm shopping for a mountain bike and I've been very intrigued by the single speed 29er's. I'm curious how single speed mountain bikes is for a big guy. I have a lot of mtb experience and have previously owned high end bikes but have only had a road bike for the past 5 years. I know most of this is determined by the riders fitness level and experience but I would still like to know your thoughts. Are single speeds only for those skinny guys you see cruising the city?