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THE INDIA RUBBER WORLD 



[May 1, 1916. 



European Pneumatic Tire Sizes. 



FRANCE was the pioneer country in the manufacture of 

 automobile tires and used millimeter dimensions conform- 

 ing with the metric system which also originated in that 

 country. .A.11 Europe followed the French lead by using metric 

 measurements in manufacturing automobile tires. 



America entered the field later, but, instead of metric meas- 

 urements, inch sizes were adopted. So today there are French 

 or metric tire sizes universally used in Europe while inch sizes 

 prevail in America. This state of affairs is regrettable, and the 

 probabilities are that for a long time to come American and 

 European tire makers will continue to use different standards. 



Nevertheless, with the tremendous impulse which the war has 

 given to the e.xport trade in American automobiles and auto- 

 mobile tires, and in view of the universal movement in favor 

 of standardization, it is of interest to briefly review the evolu- 

 tion of European practice and tabulate those sizes now gen- 

 erally in use, together with their equivalents in inclies. 

 EUROPEAN SIZES. 



Xot many years ago. when the automobile industry was still 

 in its experimental stage, practically every constructor built his 

 product entirely in his own shops and made wheels best suited 

 to the general characteristics of his machine, regardless of 

 styles and sizes used by other builders. This resulted in an 

 unlimited range of tire sizes and designs which tire manufac- 

 turers were obliged to produce and for which the motorist had 

 to pay. 



With the growth of the industry and the desire of auto- 

 mobilists to have a minimum of difficulty in obtaining tubes and 

 casings to fit their machines, automobile makers were grad- 

 ually obliged to follow the lead of certain large concerns which 

 had many machines in public use and for which dealers could 

 afford to stock tires. In other words small automobile manu- 

 facturers, to satisfy their customers had to adopt sizes used by 

 those makes of automobiles that were most widely distributed. 

 This was a first step towards standardization, but the number 

 of tire sizes remained very large. 



A leading European automobile tire manufacturer publishes 

 a catalog listing tire casings and inner tubes in 38 dii^ferent 

 metric dimensions, besides 6 American sizes in inches. Many 

 of these tires are made in an extra strong and heavy variety 

 under the name of limousine tires which are not included in 

 the 38 sizes and this list does not include what are known as 

 oversize tires, that is to say, there is no 815x120 millimeter 

 variant of the 815x105 millimeter tire. So that, taking ac- 

 count of the great number of odd sizes still in use, it can be 

 safely said that at least 50 different sizes of pneumatic auto- 

 mobile tires are now on the European market. The following 

 table gives the European sizes most widely used, together with 

 their equivalents in inch measurements: 



FRE^•CH OR METRIC TIRE SIZES. 



Sizes 



Equi. 





BRITISH rNEUM.\TlC TIRE STANDARDS. 



iMany unsuccessful efforts have been made in Europe to 

 standardize tire sizes. The principal reason of this non-success 

 has been because of the number of cars made under old con- 

 ditions and which are still in use. 



In England, during 1913, T. H. Woollen of the Society of 

 Motor Manufacturers and Traders, initiated and carried 

 through the work of reducing the number of standard rim 

 sizes to 20 that would take 38 standard tire sizes. As there 

 were 38 standard tire sizes, and several oversizes as well, with 

 only 20 rims to accommodate them, in many cases two different 

 standard sizes of tires would fit the same rim. 



In 1915, the Tire Committee of the S. M. M. T. suggested 

 reducing the number of tire rim si'es to 10 standards while 11 

 different sizes would be standardized for the tires themselves. 

 Of this range of tires two of the smallest would fit the same 

 rim while for each of the others there would be a correspond- 

 ing rim. The suggested tire standards are shown in the fol- 

 lowing table ; 



PROPOSED BRITISH STANDARD SIZES. 

 Sizes in Millimeters. Equivalents in Inches. 



These standards are now before the Engineering Standards 

 Committee, a semi-governmental institution which regulates 

 British mechanical and electrical standards, and are now await- 

 ing the final decision of this official body. 

 COLONIAL SIZES. 

 The proposed British standards, above given, do not include 

 sizes that are specially made for rough service in the Colonies 

 and known as Colonial sizes. The following sizes are most in 

 demand : 



COLONIAL TIRE SIZES. 

 Sizes in Millimeters. Equivalents in Inches. 



{ 

 Di 



Some British tire manufacturers consider a 915x105 milli- 

 incter (36.02x4.13 inches) tire as a Colonial size. 

 CONTINENTAL EUROPE. 



The lessons of the war have emphasized the advantage of 

 standardization, and reports from both France and Germany 

 indicate that serious efforts will be made in these countries at 

 least to standardize tire sizes after the war. All recognize that, 

 although standardization pushed too far may lead to the stifling 

 of originality, it is preferable to a chaos of tire sizes which 

 leads to confusion and difficulty in obtaining air tubes and 

 casings, not to mention the fact that lack of standardizatiort 

 makes tires more costly. 



