THE RUBBER INDUSTRY — GIBBONS 213 



century a life of 5,000 miles would have been regarded as high. The 

 tire of today is an enormous improvement in every respect. Many 

 of the improvements have resulted from the practical application of 

 developments which have been discussed in this paper. 



The modern tread is several hundred percent better in wear than 

 the old tread. An exact comparison is difficult to make because 

 meanwhile the increased speed of cars and increased efficiency of 

 brakes have made the task of the tread still more difficult. This su- 

 periority is a result of the application of chemistry and engineering. 

 Tread rubber has been vastly improved by the proper use of carbon 

 black, accelerators, and antioxidants. In addition to wear, the mod- 

 ern tread is much safer from the standpoint of skidding than the 

 older tread would have been. I put it this way because the earlier 

 cars, operating with low acceleration and inefficient brakes, did not 

 demand so much in the way of skid resistance as the modern car. 

 Proper engineering of the tread design has been a major factor in 

 the improvement of treads in this respect. 



In addition to the improvements in tread wear and safety, the 

 modern tread has to cope with conditions which require the utmost 

 in engineering. Freedom from noise, stability, riding comfort, easy 

 steering, low wind drift, and freedom from tramp are only a few 

 of the factors which need to be considered in building a tire for the 

 modem car and road. 



The carcass or inner portion of the tire has likewise been improved. 

 The principal difficulties in the old days were blowouts and failures 

 resulting from separation of the carcass plies. The former have 

 been largely eliminated by the replacement of the old-fashioned 

 square-woven fabric or duck by the modern cord construction. The 

 difficulties from separation have been largely eliminated by treat- 

 ment of the cord to secure better adhesion to the rubber and by im- 

 provements in the rubber compound itself, resulting from the use of 

 modern accelerators and antioxidants. 



The chemical and engineering improvements in tire building have 

 saved the consumer vast sums of money. Expressed in arbitrary units, 

 the average tire cost per 100 miles for 4 tires was 750 in 1906, and 

 by 1936 this had been reduced to about 40 — a reduction of practically 

 18 to 1. 



Let us consider the 16 years from 1920 to 1936. In 1920 the 

 tire cost per 10,000 miles was estimated at $163. This figure was re- 

 duced at a fairly rapid rate, until in 1936 the tire cost per 10,000 miles 

 was $38.30. If we assume that car registration and use would have 

 increased as they did had the tire quality and price remained at 

 the 1920 level, we can estimate the total saving to the consumer over 



