Although I haven't flattened my spare yet and won't since I relocated it this week, I now have permanently embedded clay in the sidewall. It has taken on a sick orange tint from being drug through the Ocala clay pits too many times. Since I will be replacing it in short order, I'm not too worried about it though. It just has to last another 3 weeks... huh, what's that, my front tire is flat...uh oh!