R 408.10156 Mounting depressed center wheels.

Rule 156. (1) A depressed center wheel, except as prescribed in rule 157, shall be mounted with specially designed adaptors. (2) The back flange shall extend beyond the central hub or raised portion and contact the wheel to counteract the side pressure on the wheel in use. (3) The adaptor nut which is less than the minimum 1/3 diameter of the wheel shall fit into the depressed side to prevent interference in side grinding and drive the wheel by its clamping force against the depressed portion of the back flange. (4) Adaptors affixed by the depressed center wheel manufacturer shall not be reused.