Had my first flat ever in an event at the recent South Beach event. Wasn't a blow out....just a quick loss of pressure. There was no puncture in the tire (Conti TTs) and later when I tried pumping up the tube, it held air..... and still does. As indicated, there are these three unusual markings on the tube (Vredestein latex). which are at opposite side of wheel from the stem. Wheels are two year old Enve 8.9s with the original rim strip which looked fine. I had an extender on the stem which was still tight. Any ideas?