Christopher bought a new car. He was going to travel the country with it. His friends helped him prepare for the trip. "You should carry a spare tire," said Brian. Christopher didn't see a point to that. "New cars don't need spare tires," he said. One week later, Christopher went on his trip. He couldn't wait to explore the country. Suddenly, he heard a loud pop. His car started making a strange noise. Christopher pulled over to the side of the highway. He walked around his car.