Power-Defined Accelerating Ability
The accelerating resistance at the maximum possible acceleration amax,P determined by power is overcome by the instantaneous excess traction force FX,ex. When the translational and rotational accelerated masses are considered, the following results:

Eq. 3-10

Eq. 3-11

where: ei = mass factor in the gear level i
The characteristic of the power-defined accelerating ability corresponds to the characteristic of the excess traction force when the rotational accelerating resistance (ei = 1) is neglected.
As far as the rotational masses (ei > 1) are concerned, due to the increasing mass factors at a falling gear number, the characteristic shown in Fig. 3-6 indicated by dotted lines, results. In order to achieve a high climbing ability even at maximum load in commercial vehicles, a very high ratio has to be realized in the smallest gear. In this case the value of the mass factor can be so high that the accelerating ability in the first gear is smaller than in the second.