I never stretch before any physical activity: cycling, skiing, hiking, and so on. I begin each activity slowly and work my way up to my normal operating speed as my muscles warm up. So I don't jump on my bike and head out at top speed. the first few miles are just casual pedaling. When i ski (mainly telemark) I start off on easy slopes until I'm in the groove before tackling any steep stuff. there's a lot of so-called science in the proper way to exercise, but a lot of it is just hype and an excuse for research, the writing of articles and books, and the selling of lots of unnecessary equipment. That said, if something feels good, do it. If stretching before cycling feels good, no harm in doing it.