That is, the tooth profile thus corrected to eliminate such interference. Such corrected profile is shown in FIG. 4 which shows the tooth profile of the present invention P.I., compared with the tooth profile of the prior art P.A.It is to be noted that an oval wave generator is described for oval flexing of the flexspline to obtain a mesh between the internal and external gear teeth at two lobes. This type of harmonic drive speed reducer tooth profile arrangement of the present invention is also applicable to wave generators having more than two lobes, such as three or four