Complex sentence: In May, Phinney won a stage of the Tour of California, using excellent descending skills to break away from a reduced peloton with more than 23 km until the finish, and managed to hold on to win by 12 seconds.
Split into simpler sentences: In May, Phinney won a stage of the Tour of California. With more than 23 kilometers to the finish, Phinney utilized his excellent descending skills to break away from a reduced peloton and win by 12 seconds.