  The relative bar torques for 45 galaxies observed at $K$- band with the 4.2m
William Herschel Telescope are determined by transforming the light
distributions into potentials and deriving the maximum ratios of the tangential
forces relative to the radial forces. The results are combined with the bar
torques for 30 other galaxies determined from our previous $K$-band survey
(Buta & Block 2001). Relative bar torques determine the degree of spiral arm
forcing, gas accretion, and bar evolution. They differ from other measures of
bar strength, such as the relative amplitude of the bar determined
photometrically, because they include the bulge and other disk light that
contributes to the radial component of the total force. If the bulge is strong
and the radial forcing large, then even a prominent bar can have a relatively
weak influence on the azimuthal motions in the disk. Here we find that the
relative bar torque correlates only weakly with the optical bar type listed in
the Revised Shapley-Ames and de Vaucouleurs systems. In fact, some classically
barred galaxies have weaker relative bar torques than classically unbarred
galaxies. The optical class is a poor measure of azimuthal disk forcing for two
reasons: some infrared bars are not seen optically, and some bars with strong
bulges have their azimuthal forces so strongly diluted by the average radial
force that they exert only small torques on their disks. The Hubble
classification scheme poorly recognizes the gravitational influence of bars.
Applications of our bar torque method to the high-redshift universe are briefly
discussed.
