Is it an actual 'bumper', or more of just a 'travel indicator'. On mine, I figured it was just an added feature(instead of the old tried/true wire tie around the shaft) to aid in adjusting the shocks' travel. The material it is made of, I would not think would be heavy duty enough for a bumper.. Also, the damage to the rubber piece, probably happened in the trailer while towing, not on the track...unless you tie the car down by the frame and eliminate suspension travel while transporting..

Sorry,,,after re-reading the post, I see you are talking FRONT shocks