Arizona republican., 1920-01-25

fluence on the structural design of the vehicle but automotive engineers know that it is the tires which determine the general characteristics of the vehicle they are to carry. The development of the pneumatic tire was the chief fac tor in making possible the passenger car of today.
 All except a few of the motor trucks in operation today were built from en- zine to rear axle along lines which would make them adaptable for use on solid tires. In designing these trucks, the sole object of the engineers was to secure the highest efficiency of op eration possible under the limitations imposed by the natural characteristics of solid tires.
 A small number of firms build trucks especially for pneumatics, but the number of makes of this sort is very limited The number will undoubtedly grow rapidly, for the advantages of having a truck ride on air are so ap- parent that the demand for trucks de- signed for pneumaticS cannot help but become great in the immediate future.
 A truck designed for pneumatics diff fers radically from one built for solid tires. Truck and tire engineers are now working together to solve the problem of faster highway transporta- tion and the solution is found in a truck specially designed to operate on
  responding to that of passenger car, an engine which will drive the vehicle at high speeds and still show the nec- eSSary economy in gasoline and oil, a rear axle and differential gears which will compensate for the larger outside diameter of the tires, and a braking system that is powerful enough to give the driver complete control of the heaviest truck under Sll conditions.
 It is because most trucks are de signed for operation on solids that truck users may find pneumatics un- suited to their requirements. If a truck designed for solids is changed cost of this equipment can be most easily offset by increasing the radius of action; that is, increasing the speed While the tires are designed for this the engine, transmission, differential gears and brakes are not.
 Another limiting factor that should be clearly borne in mind is that pneu matic truck tires have been satisfac- torily perfected only in sizes up to s and inches. Larger tires than this are stillsin the experimental stage.
 There are some conditions under which it is wise to changes over from solids to pneumatics, even though the truck construction contemplates the use of solids. There may be certain disadvantages as a consequence of the change, but these will be more than offset by certain advantages to be gained through use of the pneumatics.
 Because of the multiplicity of uses to which motor trucks put, it !s almost impossible to lay down any hard and fast general rule showing the con ditions under which pneumatic tires should be used or under which solid tires would be proper equipment. For information covering any particular case, the truck owner is referred to the sales and service depots of the United States Tire company.
 Pneumatic tires have certain very definite advantages over solids. It is just as desirable to have all trucks op- crate on pneumatic tires as it is to have all passenger cars operate on pneumatics. The invention of the pneumatic tire was one of the grea test steps forward in the development of the passenger car, and the pneumatic tire for trucks is as great a step for ward in the evolution of motor trucks There is no doubt that ultimately pneumatics will be the standard equip ment for practically all vehicles of this character
 The United States Tire company was the first to develop pneumatic truck tires and there can be no question to- day as to their durability and reliabil- ity. Hobby cord pneumatics have suc- ceSSfully met the tests of hard usage on thousands of trucks under the most trying conditions and have proved their worthiness, because they are and al- ways have been specially designed for truck service and are not merely an enlarged passenger car type of tire. Until trucks are designed especially for them, truck owners should hesitate about substituting pneumatics for solids unless they are sure that pneu- matics are better suited to their trucks and their needs than solids.