These aim to show groups of cars that can be raced together competitively, such that you can choose any car in say “Sports B” and have a good race with a group of people who are also limiting their selection to the same cars.
Within this section (click +Contents if on mobile), you can see a simple tier list for every raceable car class in the game. However with a lot of vehicles in each class there are often groups of cars that are close on performance. When it comes to racing in GTA Online, most classes have only one or two cars that can be used in a competitive setting because they’re so much quicker than everything else.
