Arizona republican., 1920-07-04

form and hence the saving or profit 1t will show depends largely upon the amount it can carry, or in other WordS, it's pay-load. There is a well-nlgh universal tendency to overload trucks beyond their rated capacity and it is not uncommon to find trucks carrying 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 over loads, but will last longer in such ser vice. This seems to me the most inn portant 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 or 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.
 Tn addition to the likelihood of in curing expense from over loading 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 prac- ticalIy new tires to be ruined by driv- CTS who do not stop their trucks @s soon as they begin to suspect tire trouble.
 In attempting to collect data as to mileage on pneumatics, I found many varying claims, ranging from 200 miles under adverse conditions, to 25,0OO miles on lighter trucks, over good roads with proper care. With rare exceptions the mileage delivered by fc Gar ll1 lar fl n that from pneumatics in the same class of service.
 When the earning capacity of the truck concerned is judged by the num- her of trips per day, the advantage seems to lie with pneumatic equipment provided the runs are long enough and not restricted by such factors as traf- fic congestion and delays at terminals
 As I suggested before, there are cer- tain 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 highways more easily, but dc 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 rela- tive effects of solids and pneumatics Oil tue COSL OI ODCI dllOn anu uph6GH we find a wide viriety of opinions, but very few conclusions vased on accu- rate 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 1 following items are usually not af- fected by tire equipment: Interest or 1 investment; 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; gasoline; oil; tires; re- pairs due to wear and tear and accf- dent.
 Taking them up in the order given, | there are, so far as I know, no de- 1 pendable eGures covering deprecia- | ton on which to make comparisons as no trucks have been run long enough on pneumatics to determine their effect (Continued on page ?