To easily win all the races in career mode easily (not including missions), enter the game options and do the following: set the opponent's strength down as low as it can go; and set your braking assistant on full Exit the options menu and choose a car that is easy to handle, such as an 'A Class' car. Go to a race and you never have to use the brake. Best of all, you will easily defeat your opponent every time. If you are a skilled driver, try doing the same with a very fast car.