Rattlers are a common sight on my rides in the Summer. Only very close encounter I had was on a singletrack with two other guys. I was second in line. Guy up front spotted the snack on the track and stopped ten foot past. Of course all i saw was my buddy stopping and I pulled up right behind and next to the critter. Snake just turned around and went back in the bushes. Didn't rattle at me either. Took a minute or so to get me heart rate back down. We now have a hand signal for snake!