ARCADIA, Calif. - It can be argued that Bill Shoemaker's greatest ride came on the summer day in 1991 when, in the first months of his quadriplegic existence following his one-car wreck, he successfully negotiated the hallway of a Colorado rehabilitation hospital using the sip-and-puff mechanism of his customized wheelchair. Later, he became so adept at its operation that he could run right over the tip of your shoe and make you think it was an accident.