With the warmer weather this weekend in Orange County, CA I went with friends on a 100 mile ride through the local mountains. Surprisingly, my wife who is more often that not a reluctant passenger went along. The next day I was behind the bike a noticed a shiny piece of steel in the rear tire. I rode the bike home and pulled out a one inch long shard of metal. Yeah I know, the tire should have gone flat right there. I didn't hear a leak and used soapy water to confirm that there wasn't one. The tire only has about one-third of the tread left, but with this experience I am thinking the wisest decision is to replace it now. That is unless one of you with more experience has a compelling reason to wait until the tread is worn to the point that replacement is required. I am really glad this didn't go flat in a mountain curve with my reluctant passenger on board. Could have been a nasty time. Any thoughts one way or the other are appreciated.