We were making good time up the Jackson Cabin trail until, just a few miles before the cabin, my front end seemed to wash out and I headed off the trail and into a dry creek bottom. I was trying to figure out what had happened when Craig pointed out that my front tire was flat. We used some rocks to prop my bike up and we removed the tire. We discovered that the valve stem was torn away from the tube and the tube was unrepairable. I had aired down to 15 PSI earlier, which I don't normally do. Apparently, I'd aired down too much with the Karoo tire and no rim locks. Troy mentioned that mountain bikers will stuff grass in the tire when they have unrepairable tube problems. Since we had no better ideas, we decided to try that. Here is Craig with some straw to stuff in.