A parking brake for vehicles, which guarantees safe parking from the very first time it is actuated, comprises a drum and at least one shoe intended to press against a cylindrical surface formed on the inside of the drum, recesses and projections being provided on said surface. The method involves determining the lateral diffusion error by use of a predetermined set of calibration standards. The combination enables to raise disease treatment effectiveness. In the first position, the pivot member operates as a seat for supporting a rider thereon to define a ride-on configuration.