This was a pretty simple achievement, even if you're alone. All that needs to be done is start a game as the shooter, and before the race starts, aim at a driver's front tires before they start to move. The second the race starts, shoot, and you should have it. A simple 20g cheevo.
But if you're with a friend, or have two controllers, then put them on opposite teams, with your main controller as a shooter and the other as a driver. Then aim at your guest's wheels, and shot 'em out.
Of course if you just have fun with the game, eventually you will unlock the achievement on your own agenda, while having fun!
Best of luck to anyone with this game! Hope this helps