Joy and I went to the Urban ride. As we were waiting to start, we heard a "gunshot" or a "big firecracker", sure sign someone has a blowout. We all felt our tires but nothing felt flat. Then someone noticed that I had some tube pinched between my tire and rim. That was the blowout. Changed the tube, and we were on out way. The ride went well, but as we were going up A1A near sunrise we got another flat, same wheel. When I pulled the tire I realized I had an 18 - 23 tube on a 28mm tire. The tube was overstretched. I'm just glad it didn't blow on the 17th st causeway at 30mph! As I changed the tire Ernie the Sweep came by and stopped. I put the tube in and inflated it only to have it go flat again. I figured we were out of tubes, so we sent Ernie with my keys to get the van. Just as he was almost out of sight, Joy realized that I had put the bad tube #1 back in, and we still had a good tube to fit. We called Ernie just in time and he came back. We were soon on out way. Unfortunetly I had turned off the Garmin, so we lost the rest of the ride.