In 2007 new MotoGP regulations limited the number of tires any rider could use over the practice and qualifying period, and the race itself, to a maximum of 31 tyres (14 fronts and 17 rears) per rider. This introduced a problem of tire choice versus weather (among other factors) that challenges riders and teams to optimize their performance on race day. This factor was greeted with varying degrees of enthusiasm by participants. Bridgestone had dominated in 2007 and Michelin riders Valentino Rossi, Nicky Hayden, Dani Pedrosa, and Colin Edwards all acknowledged shortcomings in Michelin's race tires relative to Bridgestone. Rossi, disappointed with and critical of the performance of his Michelin tires, switched to Bridgestones for 2008 and won the world championship in dominant fashion. Pedrosa controversially switched to Bridgestones during the 2008 season.