A few contacts but never had a real problem. Unless your blowing through at full speed you are not going to out ride a medium to large dog. Some are protecting territory and are aggressively moving you on. Keep going. Most seem to be having sport they may touch you and that's it. Keep going. But then you have the really aggressive dog you are probably going to get bit. This can be a dangerous situation and I am no CESAR MILAN but if I am going to have to deal with this animal I am NOT going to do it from a bike. If you stop and get off you are no longer sport or running prey. You may bluff him down and hope like heck the owner comes to your aid....or not. I hope I never run into this dog.