When I first started last year I was over 200lbs and averaging 12.7mph (according to my records) on the rough(crushed limestone) but flat trails. Once I got past the ~ 500mile threshold, I noticed my average speed improving, when I stopped riding I was averaging 15mph on the same trail at ~170lbs. Just imagining how heavy my bike is (I've never actually weighed it), and the fact I'm running on size 700x35 tires, I don't see that # improving any further