A model tractor based on a smaller version of a real tractor was built to study how well it could grip the ground. The model tractor could be driven with two or four wheels. Tests showed that using all four wheels gave the strongest pull, three times more than using just the front or back wheels. The back-wheel drive was better than the front-wheel drive. The four-wheel drive had more resistance to moving than the other modes. The best balance between grip and movement was found to be a traction ratio between 0.3 and 0.4.