Methods of Determining Abrasion. With Particular Reference to the Relation between Road Performances and Laboratory Tests

Abstract

Abstract Many previous papers have included descriptions of abrasion machines, but few have dealt particularly with the correlation of road performance and laboratory tests. It must be admitted in the first place that no abrasion machine, however good it may be, has yet been designed to replace road tests. None of the abrasion machines of the small laboratory type takes pattern into account, for example. Of course, there are one or two abrasion testing machines in which a complete tire is used, but they are not in favor, in view of the expense and time involved in obtaining results. Variation in Relative Road Results.—Relative road results on tread wear may be considerably influenced by external factors such as speed, road surface, front or rear wheel service, tire design, etc. In view of this possible variation in relative wear it is obviously necessary to eliminate as many of the causes as possible when comparing two tread compounds on the road. Probably the best way is to make a tire tread in two halves, i.e., one-half of the tread circumference of one mixing and the other half of another mixing; these halves joined together before curing form a perfectly sound tire. If the compounds cure at different rates, and this method cannot be employed, the best plan is to make a pair of tires of the same design and fit them, say, to the rear wheels of a car, and interchange them from near to off wheels every 500 miles. Even so, it is useless to rely on one or two tires to give the relative road results on tread wear; at least four distinct comparisons are necessary. It is not uncommon for the relative abrasion of two mixings to change during the actual course of the road test.