The Recommended Rank defines the rank requirement for a Career race. The higher your Car Rank compared to the Recommended Rank, the easier it will be for you to win. The lower your Car Rank compared to the Recommended Rank, the harder it will be for you to win. The only way to increase your Car Rank is to upgrade your car. If your rank is too low for a race, the recommendation will become red, which means that you will need to upgrade your car in order to race.