A few minutes into my run to the hardware store today, my rear tire blew out. I figured it wasn't a big deal since I could toss/patch another tube, but as it turns out, the tube blew out where the tire tore off the bead. Does anyone know how this could happen? The tire had been on/off the rim a couple times because I had improperly put the tube in and had to patch a couple small tears, but nothing that would've gone through the sidewall. When I got th bike, the tires on the Araya 700c rims were 700-23c and the one that tore was 700-20c.