You have the right idea. You can think of the weight of the car being partitioned by the angle of bank into a force parallel to the surface and one perpendicular to it. The force perpendicular to the surface adds to the normal force holding the tires on the pavement and the force parallel to the surface has a component toward the center of the curve that contributes to changing the direction of the car. On a flat track all the centripetal force would have to be provided by the friction of the tires on the pavement.
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