No metal tired vehicle, including tractors, motor trucks, traction engines and other similar vehicles, shall be operated or driven upon or over any paved or hard surfaced public street within the city if such vehicle has, on the periphery of any of the road wheels, any block, stud, flange, cleat, ridge, lug or any projection of metal or wood which projects radially beyond the tread of traffic surface of the tire; except, that this section shall not apply to tractors or tractor engines equipped with what is known as "caterpillar tractors" when such caterpillar does not contain any projections of any kind likely to injure the surface of the road; provided, however, that tractors, traction engines and similar vehicles may be operated upon the aforementioned public streets which have upon their road wheels V-shaped, diagonal or other cleats arranged in such a manner as to be continuously in contact with the road surface; further provided, that the gross weight upon such wheels per inch of such cleats in contact with the road surface, when measured in the direction of the axle of the vehicle, does not exceed eight hundred (800) pounds. (1977 Code § 12.12.010)