I think they both took the bus which is kind of how they became friends as freshmen, but didn't like to cause the bus is for losers. Then when Brooks got his licence Eric started getting rides with him.
The way Brooks tells it, he overslept, was woken up by a phone call from someone else they carpooled with, then Eric called all grumpy at Brooks, Brooks told him to get a lift some other way, but the bus had already left. Eric then had to get a lift from his dad, but they ran into Brooks on the drive to school- had words with each other and Brooks said no more lifts.