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Show " DETERMINE WEAR ON AUTOMOBILE TIRES L- ' ' - - " . Following a Tire Under Various Leads. wuicning tiirotigh clear plate glass with both the naked eye and the photographic pho-tographic camera, the bureau of standards is experimenting with a specially constructed apparatus to determine de-termine how and why the treads of autom-ibila tires wear and the effect of the axle load and air pressures. The apparatus, devised to ascertain by intimate observations the varying configurations in tire treads for the Information of the Industry, Includes a miniature car moved hack am forth on a track by rack and pinion, with tire pressing against the glass plate at varying pressures and loads. The full text of a written statement on the subject follows: Apparatus by which the wear of automobile tires in service can lie re corded and studied has Just been completed by the bureau of standards. A pneumatic tire is constructed with a thick layer of rubber around its ouler circumference to act as a wearing surface. This is cnmmonU referred to as the tread of the tire as distinguished from Ihe hoci.v of the tire, which Is designed to withstand air pressure. The ideal tread, in ad dltion to giving tractive properties to the tire, shot. Id wear down uniform ly and at such a rate that it will last as long as the remainder of the tire. From an observation of the manner man-ner In which treads wear In service as well as from laboratory tests, it is apparent that the wear is Influenced by the construction of the tire an 1 the design of the tread as well a-s h. external conditions such as road surface, sur-face, speed of operation, etc. The fact that the wear of a tire tread is influenced by the design of the tire has been emphasized by the general adoption of the balloon tire, which because of its large contact area subjects sub-jects the tread to greater distortions as It comes in contact with the road than Is usual in high-pressure tires. The bureau has built an apparatus consisting of a small car, which may he moved hack and forth on a track by rack and pinion. The body of the car consists of a sheet of clear plate glass. A tire under a definite load and air pressure may be pressed against this glass plate and observed ihrougli t lie glass. Ily running the car along the track while the lire is pressed against it Ihe distortions of ihe tread corresponding to the action in service can lie se"'j and phnlo graphed. |