I read a recent study, think it was done in the UK...anywho. They said they determined after 6 months, or a 1yr, whatever the length was, of pre-ride stretching, or pre-anything stretching for athletes, didn't make them less prone to injury at all.

In fact, they found that stretching actually caused more fatigue and less performance for endurance athletes, because the stretching is actual physically straining, and you cause/create micro muscle tears when doing it.

With that said, there are some stretches I do a few times a week, next day after a ride, few days after, to ensure some typical cycling flexibility things you should look into. Plenty of stuff on the web and in the thread relating to that.

I do some basic warm up techniques to get the blood flowing/heart rate up to start a warm up, then do a 15 minutes tempo pace up to get warmed up and increase speed. I've found this to be the key for my peformance personally, no stretching pre-ride/race...but a good longer warmup and sweat.