When you turn left, the left wheel angles down and the right wheel angleds up. This action causes a weight transfer to the right rear and takes weight off the left rear. In Sprint racing, where both rear wheels are the same diameter, it's the only way you can get a kart to turn. If you didn't take the weight off the inside rear wheel, the kart would go straight when you try to turn. It also makes the wheels point straight ahead even if you don't hold on to the steering wheel. That's in a Sprint kart of course, not a dirt kart. Dirt karts have stagger, and that will cause the kart to turn by itself.