The "U" was the first Allis-Chalmers tractor to be painted "Poppy Orange" rather than dark green. The "U" was also the first production model farm tractor to offer pneumatic tires. Pneumatics were more comfortable and let the tractor be driven at higher speed on the road but most important they required about half the power in the field. It wasn't long before all manufacturers were offering them on their tractors.
