+1 on autumn riding. My daily commute route takes me on city streets for half a mile and then through a large apartment complex to hook up with the bike trail heading downtown to my job. Just before I get to the trail there is a really large speed bump and I always thread my way between one end of the speed bump and the curb and though it's a narrow passage I'm going uphill at a pretty slow pace. Last year about this time I was making it through the chute and there was an accumulation of leaves at least 6" deep and as I rolled into the pile my front wheel rode up onto a black walnut with the thick, green skin still attached and I immediately pitched over onto my side with no chance to get out of my toe clips. My shoulder, elbow and hip joints were sore well into the new year from what had to be a crash at no more than 2 mph.!!