A friend put my bike (roadie 700C) on their car rack (towbar one) and told me to let the tyres down a bit in case they blow out due to the hot temperature (30 deg C +). I laughed and said what difference is there to riding on a hot road, that should be hotter and I've never had a blowout because of heat. Then today I had the bike in the back of my car because I was planning to go racing after work and it was a hot day (32 deg C +) and when I came out to the car at 5pm the rear tyre of the bike was flat. This has actually happened to me at least twice before but I just put it down to a piece of glass or other debris still in the tyre from a previous puncture. But this being the third time I'm thinking that maybe my friend is right and the heat is causing a blowout. The latest 'puncture' seemed to involve the valve splitting away from where it joins the tube (Conti brand tubes). I'm thinking too that Conti tubes might be a bit thinner and lighter than the other cheapo tubes I have previously been using therefore exasperating the problem. Anyone else experienced this?