A device includes a plurality of tires and a suspension system as subcomponents. The suspension system includes at least one suspension sensor configured to provide suspension data (S). A controller is operatively connected to the suspension sensor. The controller has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method for determining respective tire normal forces (Fzi(t), i=1 . . . 4) for one or more of the plurality of tires, based at least partially on the suspension data (S). The tire normal force (Fz) is the net force acting on each tire (or wheel) in the vertical direction. The tire normal force acting on each tire may be determined without using the specific model of the tire, road information, wheel or tire sensors.