Hello all. I'm an overweight (5'11" 250lb) rider who has recently started riding a lot more. I bought a bike for the first time since college about 6 months ago and started riding fairly short/daily trips to the train station (I live in a small city in Japan). About a month ago I worked up the endurance to start commuting to work (7 miles each way). Since then, I have had some issues with flats. In one month I have managed to have 4 flat tires. 2 were blowouts, two were punctures. I ride a Trek 29er MTB (I grew up mountain biking and was comfortable with the brand/style). I do a good portion of my route on the sidewalk (its also the designated bike path) next to a major road because the road is not great for riding (traffic!). This means lots of bumps and ups and downs etc but I figured hey, mountain bike, there ya go. Anyway, I am wondering, does anyone know what could be causing my blowouts/me to get punctures so easily or what I can do to avoid them? If it is a result of my weight, that makes sense, but the guy at my local shop assures me that it should be fine. As this is an introduction thread, I'll likely be posting this question elsewhere later but thought I'd throw it up here anyway.