Mohave County miner and our mineral wealth., 1920-07-03
RELATION OF SOLID AND PNEUMATIC
 TIRES TO MOTOR TRUCK EFFICIENCY

it is not uncommon to find trucks car rying twice their rated capacity. When it comes to standing up under this usage, there seems to be no doubt that solid tires will not only carry heavier overloads, but will last longer in such service. This seems to me the most important and least understood factor in the entire list. Apparent savings may be offset or overbalanced !, by the additional trips that become necessary when an overload cannot be carried.
 Closely allied to the cost of over loading pneumatic tires is that of un- der-inflation. The constant and ex- treme flexing caused by overlooking has a tendency to weaken the side wall, making it much more likely to fail in service. While solid tires are not invulnerable they can stand more abuse and are less expensive to main tain in working condition.
 In addition to the likelihood of in- curing expense from overlooking and under-inflation, there is the danger of running pneumatic tires from running them after being punctured or blown out. It is not uncommon for practi- cally new tires to be ruined by driv- CTS who do not stop their trucks as soon as they begin to suspect tire i trouble.
 In attempting to collect data as to mileage on pneumatics, l found many varying claims, ranging from 200 mil es under adverse conditions, to 25,OOO miles on lighter trucks, over good roads with proper care. With rare exceptions the mileage delivered. by solid tires is considerably greater than that from pneumatics in the same class of service.
 When the earning capacity of the truck concerned is judged by the num- Der of trips per day, the advantage seems to lie with pneumatics equip ment provided the runs are long enough and not restricted by such fac tors as traffic congestion and delays at terminals.
 As I suggested before, there are certain conditions under which trucks on pneumatics can make trips when those on solids can not be operated Hence, their earning capacity is just so much greater. It has been noted that trucks on pneumatics not only negotiate the unpaved roadways more easily, but do less damage than those on solids, and hence are looked upon with more favor by the farmers they serve.
 When we come to consider the rel ative effects of solids and pneumatics on the cost of operation and upkeep we find wide variety of opinions but very few conclusions based on ac- curate cost records.
 Let us examine briefly the items (which should be included in such costs, and see how they are affected by solid and pneumatic tires The fol- lowing items are usually not affected by tire equipment; in terest on invest ment; insurance; taxes and license; garage; supervision; wages of driver and wages of helper.
 The following, however may vary according to the type of tires used: depreciation; gasolinea oil; tires! re- pairs due to wear and tear and ac- cident.
 Taking them up in the order given, there are, so far as know, no depen- dable figures covering depreciation op which to make comparisons, as no trucks have been run long enough on pneumatics to determine their effect on the ultimate life of the truck.
 As to the relative consumption of gasoline and oil, very few reliable fig ures are available, but the best in