Dog's disturbing cycle

My rescue dog is now 18 months old.

- 

He is well behaved at home but has developed a worrying habit. He seems to enjoy chasing cyclists and I cannot take him anywhere near them. He doesn't try to bite but jumps up at them. Why does he do this, could he grow out of it and if not, where can I get help?This is a very common problem, especially in young rescue dogs. It is possible that your dog missed out on the early puppy socialisation period around t