Using Stokesian dynamics simulations, the shear-induced diffusivities due to pair collisions of identical spherical or nonspherical particles are considered, with the purpose to evaluate the effects of irreversibility and symmetry breaking. Results are compared to an approximate upper bound found by assuming that the particles leave the collision at their maximum separation. For spherical particles, the effects of surface roughness and a short-range repulsive force are considered. For nonspherical particles, a short-range repulsive force is used and effects of shape are considered. In general, it is found that at small repulsion (range of repulsive force, rc, equal to 10−6 the particle radius R), the shape of the particle has a large impact on the shear-induced diffusivity, so particles with broken symmetry have diffusivities that are up to five orders of magnitude larger than those of spheres. At high repulsion (rc = 10−1R), however, the effect on the particle shape on the diffusivity is not as strong and all particles have diffusivities with the same order of magnitude.