I have to replace my valve stems today. I was checking the tire pressure and they were a little low. Got the compressor going and when I started to add air the valve stem pushed to the side a little and I could see all kinds of cracks in it from dry rot I guess. Tires look great no cracks at all. I keep 303 on the tires but never had put any on the stems. Next time you check your tires take a look at the stems too. Might save some trouble later.