To assist tracking of the belt it is advisable to crown the drive pulley. When considering drives with minimal difference between the pulleys’ diameters or with vertical or semi-crossed drives, it is advisable to also crown the smaller pulley, decreasing the h value by half. With multiple pulley drives, the pulleys to be crowned are only those touched by the same face of the belt. It is important to crown the pulley (s) as shown in the figure below. Do not fit pointed or truncated cone-shaped pulleys.
Materials recommended: cast iron or steel with smooth surface finish. The dimension h is a value of the pulley diameter up to 400 mm (see table 1).
For Ø >= 400 mm, h is a value of the diameter Ø, as well as the face width b of the pulley (see table 2). Usually the belt width recommended is as a minimum 10 mm narrower than the pulley face width.

1) Dimensions for pulleys having diameter D from 40 to 355 mm.
The values of the dimension h, related to the diameter D, are shown in the table herebelow (ISO R 22 / DIN 111):

2) Dimensions for pulleys having diameter D from 400 to 2000 mm.
The values of the dimension h, related to the diameter D and to width b, are shown in the table herebelow (ISO R 22 / DIN 111):