The DLC adds 4 new AR Racing Challenges on 2 new tracks as well as a new Batmobile skin, inspired by the 1989 movie.
2 of them are 1 lap races and 2 of them are 3 lap races.
I suggest to do the 1 lap races first, since the last lap of the 3 lap race is mostly the same as the 1 lap race. This last lap is always the hardest and if you're experienced in it, it will help you to finish the 3 lap races faster.
Finishing all 4 of them rewards you 12 AR Stars, so you will have to finish another 7 AR Challenges 3 stars with the 1989 Batmobile Skin. To change the skin, head over to the AR Challenge and press
to switch through available Skins.
You will have to finish 5 more Racing challenges and 2 Search and Destroy Challenges from the Batmobile Hybrid Tab. Stars are tracked seperately per skin, so you won't have to worry about tracking your progress.
mentioned in the comments, the 12 stars of these new tracks work towards the Absolution Achievement (Achieve 69 Stars in AR Challenges
As wes coasn
mentioned in the comments, the new tracks added with the 2008 Tumbler DLC can be finished with the 1989 Movie Batmobile and therefore makes the 33 Stars needed for this achievement easier.