It is very difficult to measure sidewall angles. These angles change as the belt is bent, and the sidewall and top surfaces are not always perfectly flat -- thus making the measurement difficult. Also, belt angles will change slightly as the belt is run in the pulleys, making comparison of a new belt to a used belt meaningless.
Belt angle is a very important belt dimension which can significantly affect performance and belt life. Gates has spent a great deal of testing resources optimizing the angles for the constructions of our two aftermarket belts. Because of the importance of this variable, our manufacturing tolerances are maintained to an absolute minimum.
It is important to understand that each belt construction dictates its own angle system and it is entirely possible that belts from various suppliers will have slightly different angles.