A seal assembly includes an annular inner casing disposed on a shaft and including an axial portion and two radial portions. An annular outer casing is disposed about the inner casing and includes an axial portion engageable with the body bore and a radial portion. An annular elastomeric seal member is coupled with the first radial portion of the inner casing and is engageable with the outer casing axial portion. An annular bumper has a fixed end coupled with the outer casing radial portion and a free end disposed adjacent to the inner casing second radial portion. At least one spacer extends from the bumper free end and is disposed against the inner casing second radial portion or within an opening through the inner casing second radial portion. The spacer(s) are detachable from the bumper when one of the inner and outer casings angularly displaces relative to the other casing.