Reversible steering gears, irreversible and semi-reversible. Steering gears in terms of their properties can be divided into reversible, irreversible and semi-reversible. The reversibility of the steering gear results from the appropriate selection of the inclination of the thread turns in helical gears or the spiral of the worm in worm gears. By reversibility is meant a property of the steering gear, consisting in the tendency of the steered wheels of the car to set itself to driving straight ahead, when a laterally turned steering wheel is released. The irreversible gear, on the other hand, works as self-locking, i.e.. essentially turning of the side steerable wheels, as well as returning to straight-ahead driving requires the same effort. A certain facilitation of the return of the wheels to driving straight ahead is achieved only thanks to the appropriate setting of the front wheels. Often in modern cars, intermediate type steering gears are used, i.e.. semi-reversible. Such a transmission ensures, to some extent, the tendency of the steered wheels to move straight ahead, while minimizing vibrations in the steering wheel (in the reversible transmission, they are transferred to the steering wheel when driving on uneven surfaces (lateral vibration of the front wheels).