How do you unlock 2011 season in nascar the game 2011

I found this out when I was playing one time. If you have already bought the 2011 season from the marketplace or from online, you need to restart your 2010 season (if you have already started one). After you restart and try to start the season over, it should give you the option if you want to race the 2010 or 2011 season. Then, you can choose 2011, and if you do, that is when you can race the 2011 cars online. If you do that, you cannot race the 2010 cars, and if you want to race them, you have to switch back to the 2010 season. Hope this helps you!
~Wes~