The format was changed for GP 2005 with 16 riders (instead of 24) taking part in each Grand Prix event, and over the course of 20 heats each rider started in 5 heats and raced against every other rider once (which is the classical round-robin formula of the individual tournament).
GP 2005's format changed from 24 to 16 riders per race, and the racing structure was based on a round-robin system with each rider competing in 5 heats against every other rider once.