Tractor tires mounted on stock wheels. The ones in front are mounted correctly so that the tires grip well when braking. The ones in back are mounted to provide more traction under power. Whoever mounted the tires knew what they were doing.
As tall as those tires are that would definitely be a poor man's overdrive theoretically the top speed of that thing is probably about 80 miles an hour if it had the power to turn that speed!!!