Arizona republican., 1920-07-04
RELATION IF SOLID AND PNEUMATIC
 TRES ID MOTOR TRUCK EFFICIENCY

Tn the first installment of this ser ies the mechanical features involved in changing from solid 10 pneumatic equipment were discussed. Let us now look at the practical operating features that must be considered in de termining which type of tire will make the truck most efficient in service
 Broadly speaking, the efficiency of a truck in performing its function de bends upon the amount of time or money, or both, that it saves for the shipper, as compared with any other means of hauiage. While it is diff . cult to separate all the factors bear ing on thesei two items. they may be roughly classified as follows:
 The factors effecting time are: Dis tance Of hauls; traffic congestion' speed Of delivery; regularity of deliv- cry; condition Of roads-(effect on speed of truck; number of trips per day, and time out for repairs, etc
 The factors effecting money are: Amount Of pay load and overload; con dition of road-(effect on tires and truck); number of trips per day; cost Of operation; cost of upkeep, and cost of substitute equipment.
 Tn what way does the tire equip meDt bear on these nactors2 To begin with, the operator must pay from 75 per cent to 225 per cent more for pneumatic than for solid tires. No dependable figures indicating the rela- tive cost per mile of the two types are avilable, but from such information as can be obtained, it is my belief that it will cost from two to three times more per mile to run on pneumaticsY than solids.
 Let us see how pneumatic tires may effect the time factors If the opgr- ator is engaged in long distance haul ing with relatively few stops. pneu- matic tires will almost invariably save running time, due to the fact that they absorb the road shocks so much more easily than solids. It should also be noted that the drivers fatigue in such cases is far less on pneumatics than on solids.
 Up to the present, however, conlpar atively few trucks are engaged ih long distance hauling. The great ma jority of trucks operate in cities where they cannot possibly obtain a speed of over ten miles an hour. For such speeds there can be no possible saving in time which would offset the extra cost of running on pneumatic tires.
 The condition of road surface has a very important bearing on the time element, as it has a direct effect on the speed of the truck. In fact, under certain circumstances the increa ased traction afforded by the heavy duty pneumatic makes it possible to operate the truck while if it is equipped with solids it cannot be driven at all. This is particularly noticeable in rural dis tricts where there are no hard-sur- faced roads.
 One of the advantages frequently mentioned in the greater number of trips per day which may be obtained from a truck equipped with pneu- /natics. So far a s this factor by it self is concerned, there is no--doubt that the advantage is in favor of the pnauTnatic
 There is one more important factor to be considered as affecting the time element. and that is the number of hours the truck is laid up for repair. Barring occasional lay-ups caused by defective material or workmanship. solid tires can be depended upon to give uninterrupted service from the time they are applied until worn down to the point. They can then be re- placed without serious loss of time.
 Owing to the comparative vulner- ability of pneumatic tires, they are far more likely to require time out for repairs and replacements.
 Punctures do not seem to be so ire quent or so costly in point of time ,ds blowouts due to cutting and chaffing g of sidewalks from ruts, as well as to under-inflation and overlooking.
 When we come to compare the time out for causes other than tire trouble, we find a variety of conflicting claims, though it seems to me the evidence favors the use of pneumaties.
 It is claimed by some that the use of pneumatic tires acceIerates the wear on certain parts, such as bearings, bushiugs and steering kunck1es, and that a correspondingly greater amount of time required for the adjustment renewal Moreover, many owners state that the use of pneumatics on trucks cause their drivers to over
 To q chances that result in accidents and time out for otherwise unnecessary re- pairs than is the case onAsolids.
 The amount of work truck can per