Once on our annual WI trip I was lagging behind the two leaders (in a hilly section) and was really struggling on some of the hills. They had apparently awakened a dog who was waiting when I came along. By far the BIGGEST dog I've ever seen. I was climbing a hill as I passed his house and he came out to chase me. His footfalls sounded like a horse coming up behind me. I couldn't speed up and was barely moving on the steep hill. That dog's shoulders were at the same level as my 55cm bike top tube. He growled and hung close while I struggled up the hill. I tried to talk to him in a confident but soothing voice ("You're OK, big guy" "Be cool") all while sucking wind. He could have torn me apart right there, but he didn't.