The paper deals with the problem of the importance of the tooth belts pitch for the dynamics of the transmission with the tooth belt. For many years there have been defined pitches of tooth belts, previously reserved for belts made of rubber and another pitches for belts made of polyurethane.

In recent times this division doesn’t apply and in addition there are belts with pitches which previously hasn’t existed e.g. HTD9M or AT15. The paper presents a parameter that makes the wheel diameter dependent on the number of teeth involved in the coupling with the pulley. It is the equivalent of the coverage coefficient occurring in cylindrical gear transmissions. The previous elaboration about this parameter didn’t take into account unevenly placed teeth on the width of the belt.

The occurrence of the new pitches is possible in "high volume" applications and occurs more and more often, therefore it’s important to remember about the consequences connected with the changing of the pitch of the tooth belt in the belt gears.

Keywords: tooth belt, belt pitch, coefficient of coverage