OCTODER I, 1913.] 



THE INDIA RUBBER WORLD 



Gaining Better Mileage From the Motor Truck. 



During the past two years tire manufacturers and the trade papers have had much to say in regard to the compara- 

 tively poor mileage obtained from truck tires. It is the opinion of tire specialists that truck makers have been equipping 

 with too light tires for the loads they are called upon to carry. Heretofore this has been more or less a matter of con- 

 jecture; but the concrete examples given below prove the wisdom and economy of adequate tire equipment. 



IT has been conclusively demonstrated that, next to the driver's 

 wages, the largest single item in the cost of operation of 

 a motor truck is the cost of tire replacements. This is 

 even found to be the case in most electric commercial vehicles 

 where the cost of keeping the batteries charged was for a long 

 time considered to stand next to the driver's wages as an item 

 of expense. For the past two years the subject of solid tire 

 wear and destruction has been closely studied by the National 

 .\ssociation of .Kutomobile .Manufacturers and its successor, the 

 .\utomobile Chamber of Commerce, as well as by tire manu- 

 facturers and the heads of establishments which are large users 

 of motor trucks, with the object of ascertaining the factors 

 which have a direct bearing upon or control the mileage ob- 

 tained from the various types and sizes of solid tires. As a 

 result of these investigations tire manufacturers, as well as 

 motor truck engineers, have come to the conclusion that by the 

 adoption of proper methods of operation and the use of proper 

 sized tires, the users of motor trucks can greatly increase their 

 tire mileages and thereby cut the cost of operation and mainte- 

 nance very materially. 



The study of this question has included an investigation of 

 the effects of paving conditions and topography in different 

 cities of the United States from the .Xtlantic to the Pacific; the 

 greater mileages obtained from solid tires of the same size and 

 under the same loads in European countries; the effects of 

 overloading and excessive speed; improper distribution of loads; 

 diameter and shape of tires ; inadequate tire equipment for load 

 capacity, and several other factors bearing upon the subject. 

 The most important of these, which relate to the wearing quali- 

 ties of tires is, without doubt, the proper size of tires for the 

 load which they are to carry. 



It is quite evident that anything that will tend to materially 

 increa.se the tire mileage will at the same time reduce the 

 operating expense more than any other factor. Manufac- 

 turers offer guarantees on their tires of from 6,000 to 10,000 

 miles, giving an average guarantee of 8.000 miles. As a matter 

 of fact, motor truck operators have not been getting this mile- 

 age out of their tires for the simple reason that they have been 

 replacing worn out equipment with others of inadequate size. 

 The average solid tire mileage in twelve principal American 

 cities, derived from more than ISO reports on the tire equipment 

 of various sizes of trucks, both gasoline and electric, as re- 

 ported by the National Association of .Vutomobile Manufac- 

 turers several months ago, is a little over 7,000 miles. In six of 

 these cities the average was from 1,500 to 4.400 miles less than 

 the average gtiarantee of 8,000 miles. 



While it is conceeded that the nature and condition of the 

 street paving have much to do with the e.Kcessive tire destruc- 

 tion and wear, it has been proven by actual demonstrations, 

 extending over periods of from a few months to two years, that 

 overloading and inadequate tire sizes are even greater factors, 

 as will be seen upon analyzing the appended table. These figures 

 have been compiled by one of the prominent tire manufacturers, 

 and they set forth the mileages obtained with different sized 

 tires, the trucks in each case operating tmder precisely the 

 same conditions as to load, pavement, driver, etc. 



.\ltho the average mileage obtained from solid tires is 

 8,000. many cases are reported where this figure has reached 

 15,000: and where the truck owners take particular pains to 



analyze the conditions under which their vehicles operate, and 

 take steps to correct any abuses by the drivers, mileages as 

 high as 30,000 have been obtained. For instance. The London 

 Omnibus Co. reports that in many cases the tires on its 

 vehicles show 30,000 miles of service. In these cases, however, 

 the vehicles are probably those which operate in the heart of 

 London where the pavement is of the best asphalt or wooden 

 block. It should also be stated that particular attention is 

 paid to the efficient operation of these vehicles ; and the fact 

 that they are adequately equipped with tires of proper sizes is 

 probably the factor which plays the most important part in 

 their long service. 



A few specific instances will be cited to show the effect of 

 increasing the tire sizes where the original sets have shown 

 poor efficiency. In all cases it will be seen that where larger 

 tires have been substituted the percentage of increase in the 

 resulting mileage far exceeds the percentage of increase in 

 the size of the tires as well as the increase in cost. This fact 

 alone argues strongly in favor of using as large tires as the 

 operating conditions will warrant. 



One striking example of the results received from tires not 

 large enough for the load, as reported by a prominent tire 

 manufacturer, is furnished by two 1^-ton trucks operated by 

 The Texas Co., one in Fort Worth and the other in Dallas. 

 The rear wheels of these trucks were equipped with 3-inch dual 

 tires, all of which failed in a little over 3.000 miles. When 

 the manufacturer began studying the situation and had 

 the trucks weighed, it was found that each wheel had been 

 overloaded by 858 pounds. The old 3-inch tires were conse- 

 quently replaced with 4-inch tires, which have given more than 

 10.000 miles and are still running. They have worn down evenly 

 and smoothly and afford one of the best examples that could 

 be desired to show the economy of using tires large enough to 

 carry the load. Furthermore, these trucks always carry the 

 same load, being built to accommodate a certain number of oil 

 containers. 



.Another example is furnished by a three-ton truck operated 

 by the National Refining Co. of Indianapolis. This truck was 

 originally equipped with 36 x S-inch single front tires and 36 x 

 4-inch dual rears. While using this equipment the company was 

 changing the tires every two or three months until persuaded 

 by the manufacturer to adopt larger sizes for the rear. This 

 advice was accepted, as a result of which the new tires have 

 been in service for more than a year without a single change. 



.\n ice company was operating a three-ton truck equipped 

 with 36 X S single fronts and 36 x 4 dual rears, and during the 

 busy months of last summer this truck traveled about 200 miles 

 a day, being compelled to change tires every two or three 

 months. The rear tires were finally changed to 36 x 5 duals 

 during March of the present year, since which time the truck 

 has been running 24 hours a day, delivering 84 tons of ice. 

 During the six months of use the tires show only slight tread 

 wear and are still good for several months. The manager 

 of this company reports that he is pleased with the service 

 received from the larger tires and that their installation stopped 

 the delays which were frequent last year. 



The Jackson Brewing Co. of New Orleans operates, among 

 other vehicles, a three-ton truck which was originally equipped 

 with 4-inch tires front and 4-inch duals rear. Before one half 



