My girlfriend rides her Trek 1000 year around and seems to get a lot of flats. Probably one every 3 days to a week! They happen on both wheels and generally are failures around the valve stem. Not stem seperation, but what looks like serrated scuffing from the stem threads or wheel on the thick rubber base around the stem. Whenever I have flats on my Trek 5000 they generally are similar in cause. What's the deal? Is it because we're using the fully threaded Bontrager tubes, or is there some sort of tape that we could build up around the valve stem opening or on the tube itself? Thanks.