We propose that the reason Motor O simulations face the dilemma of either underestimating the THI rate constant or using unrealistically soft bonds and angles is that the 12th power repulsion of the LJ functional form is unrealistically steep and therefore overestimates the van der Waals repulsion between the rotor and the stator during THI. For Motor O, among the scanned QM conformations, the closest distance between the rotor methyl H and the stator H on C12 is as close as 2.0 Å, well below the minimal-energy distance of 3.0 Å for this interaction in the force field, and well into the range of distances where the 12th power repulsion becomes problematic. Motors S and N, in contrast, have a puckered and more flexible stator, and thus can alleviate this repulsion during THI, making the LJ repulsion acceptable for simulation of these motors.