<div class="section abstract"><div class="htmlview paragraph">AFTER making an extensive examination of many brake lining materials, Mr. Oetzel comes to the conclusion that no short test can show adequately the characteristics of a piece of lining.</div><div class="htmlview paragraph">It seems that no one value of coefficient can be used to represent a piece of lining, according to the author, because the coefficient varies so widely with temperature and pressure and with the degree of service curing.</div><div class="htmlview paragraph">He says further that there seems to be no way to reduce the characteristics of a lining material to some simple “index number”; that the best that can be said is that, when correlated with road tests, characteristics determined from samples form a useful basis of judgment.</div></div>