If you are doing it legitimately. In race mode.
The thing with the online racing is, when you keep winning you start further back on the grid.
If you are having trouble competing, People tend to ram you or get in the way at the start. Quit out of the lobby after about 4 or 5 wins and search for another game and you will start at the front of the grid again.
Even if you end up back in the same lobby you will start towards the front.
Getting to 75 shouldn't take more than about 6 or 7 wins. Depending on the amount of people in the race.