N.Y. Comp. Codes R. & Regs. tit. 15, § 53.4 – Determination of coefficient-of-friction class coding.

(a) For purposes of identification of brake linings according to their different friction characteristics, a letter code shall be employed. There shall be two conditions under which coefficients are classified: normal friction and hot friction. The following letter codes shall be used to describe coefficients of friction:
C—Coefficient of friction over 0.05 but not over 0.15.
D—Coefficient of friction over 0.15 but not over 0.25.
E—Coefficient of friction over 0.25 but not over 0.35.
F—Coefficient of friction over 0.35 but not over 0.45.
G—Coefficient of friction over 0.45 but not over 0.55.
H—Coefficient of friction over 0.55.
(b) The coefficient of friction of each lining shall be identified by two consecutive letters, the first to represent the defined level of normal friction and the second letter to represent the defined level of hot friction.
(c) The normal friction coefficient is that coefficient which is the numerical average of the four points located at 200, 250, 300 and 400F on the second fade curve of the plot sheet on which the average of five test runs is plotted.
(d) The hot friction coefficient is that coefficient which is the numerical average of the following 10 points on that plot sheet on which the average of five tests is plotted: points at 400 and 300F on the first recovery run; points at 450, 500, 550, 600 and 650F on the second fade run; points at 500, 400 and 300F on the second recovery run.
(e) If any temperature point or points required to calculate friction coefficients are not reached in the prescribed time limit, the coefficient of friction value at 10 minutes shall be used to give the full number of points required.