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Show GUARD AGAINST STONE BRUISES This , Form of Injury to Tires Is One of Most Common and Expensive to Owner. BREAK IN FABRIC IS INSIDE Inexperienced Driver Who Gcta Hard Bump Against Carb or Any Other Object Usually Look, for In-Jury In-Jury cn the Outside. A "atone bruise" la the term used to describe an Injury to a tire caused by striking some object with sufficient fonce to cause tbe tire fabric to be broken. It need not be a stone that causes the damage. The break In the fabric may be In only one ply or It may be la all of them ; but In any case It la always tbe Inside ply that breaks first. An Inexperienced driver whose tire gets a heavy blow from a stone or a curb usually looks over the outside of the tire to see If any damage has been Bump Against Curb Will Cause "Stone Bruise." done. But the old driver knows that If barm has been done the place to look for It is in the inside and that any break In the fabric will be registered on the Inside ply first. Inside Ply Shorter. Normally the Inside ply Is shorter j than the rest and each ply is shorter than any of the others which are located lo-cated outside of It. This Is because it Is on the inside of the curvature of the tire. Now if the tire Is suddenly compressed com-pressed at some point to a considerable extent, "such as shown la the lllustra,-tlon, lllustra,-tlon, the relative position of the piles Is reversed; that la, the ouslde ply becomes, at this particular point, the Inside ply as regards the curvature and the Inside ply becomes the outside ply as regards curvature. If it should happen, as It often does, that only one or two Inner piles are broken, there will not be any signs of the injury on the outside until a considerable con-siderable time afterward. This Is because be-cause the other plies still unbroken will continue to hold against the air pressure pres-sure even though they will be under excessive strain. But continued flexing flex-ing will eventually break them also, and the result may be a blowout, which may occur at any time, even on a perfectly per-fectly smooth pavement Other Effects. Another effect of a break In one or two Inner pllea may be that from continued con-tinued bending the broken edges of tho fabric nib a hole in tbe inner tube at that point Sometimes the break la so pronounced, especially In a fabric tire, that the air pressure forces the Innet tube Into the break, and as this Is continually con-tinually closing and opening, aa the tire rolls, the action la like a pair of pinchers and cuts (he tube. If the tube Is chafed through or cut aftwr a bruise, such as described, the air will pass directly through the carcass car-cass and force the rubber side covering, cover-ing, , and sometimes the tread, loose from the fabric. When this happens the user generally terms It a blowout, and as a matter of fact It Is ; but contrary con-trary to tbe opinion often held, It Is seldom the result of a defect In manufacture. manu-facture. It can generally be traced to an Injury sustained some time prior to the final breaking down of the tire. |
