To get this, along with all the other level 7 related achievements, you must get each of engine, stability, wheels and traction to level 7. Obviously, collecting money is the easiest way to get these, but front flips and back flips will net you $50 each time you complete one. Air time will also help you along with the money, as will reaching checkpoints, although these only count once.
You will need a total of $55,600 to upgrade each vehicle to level 7. Coins won on other levels will not transfer.