Mr. Byrne, 57, cuts a dashing figure. His hair is not so much gray as a spiky, incandescent white, part gracefully aging rock star, part phosphorous bomb. He wears white pants, white shoes and a bright orange vest beneath a dark blue jacket. It is hard to picture him in spandex. Even his bike, a hybrid, has personal flair. The handlebars are modified to allow him to sit up more straight as he rides. ďSince Iím not riding for sport, I kind of like to see where Iím going,Ē he said.