Tire Standards.
Page 1
If you've noticed an error in this article please click here to report it so we can fix it.
The early adoption of standard loading per unit of mass is to be anticipated on the part of manufacturers of solid-rubber tires. This intention, of which a "One Hears" paragraph gave advance intimation a week ago, deserves a welcome at the hands of owners and users. Too many running troubles have in the past been in fact ascribable to gross overloading of the tire-sections that were employed, and we cannot pretend to think that motor-vehicle manufacturers are not in a large measure themselves to blame for the dissatisfaction which we have in mind. The tiremaker is ever ready to sell the next higher section than the supposed normal for a particular load, but the price-cutting tactics of the vehicle salesman often thwart his laudible desires. The new buyer in his novitiate stages hearkens to the allurement of the lowest inclusive price, and finds that he wants a new set of tires after 3000 miles, or less, of running. This old folly, of a truth, dies hard.
We have enjoined, for more than eight years, the wisdom of the large-section tire, and we are well aware that there is no better method of keeping down mileage costs or of insuring regular service. Numerous readers of THE COMMERCIAL MOTOR have testified to the savings that have resulted from observance of our advice. The. increase, for example, from 120 mm. to 140 mm., on a three-tanner, frequently yields a life of 14,000 miles compared with 8000 miles, for the driving wheels, whilst the increased cost is not more than 25 per cent. We give below some data for loading according to present-day practice. This is very good, so far as it goes, but the load per unit of mass (volume) of rubber in the complete tire still remains undetermined. That is not satisfactory to user or vendor. The Tire Section of the Society of Motor Manufacturers and Traders will have conferred a real boon upon every owner, when its labours on this subject are completed, and when the ultimate agreed maximum figure for loading, expressed in lb. per cubic in. of tire, is announced. The following are common width and depth measurements, for band tires, for the axle-weights (not gross vehicle weights) which we give 10 cwt., 56 mm. by 44 mm._; one ton, 75 min. by 60 mm. ; two tons, 110 mm. by 75 mm. singles, or 75 mm. by 60 mm. twins ; three tons, 87 mm. by 65 mm. twins ; four tons, 100 mm. by 75 mm. twins; five tons, 120 mm. by 80 mm. ttirins ; six tons, 125 mm. by 85 mm. twins ; seven tons, 140 mm. by 90 mm. ; and eight tons, 160 ram. by 100 mm. twins. One maker is now offering 290 mm. by 90 mm. tires, for use, as twins, under axle-loads of six tons or more. The diameters, of course, must not be under the normal, or the greater frequency of contact with the road, and therefore of reversal of stress, must be met by the adoption of a larger cross-sectional area of rubber material. Small-diameter wheels add to tire wear and tear. The agreed loading is likely to be fixed at an intensity of between 1-i lb. and 2 lb. per cub. in.
We regretfully admit that owners sometimes do not "play the game" about loading. Mileages, in the ease of maintenance contracts are one bone of contention: loads are another. We have good reasons for anticipating more applications of the " Easyweigh " hydraulic jack, which costs only about 27 10s. and weighs as it lifts, as a means of checking these short-sighted practices.