Why did both of my inner tubes blow out on a new bike I've only put 4 hours on? I bought a new Diamondback Trace hybrid bike about a month ago. Rode it twice for about an hour a piece and the last time for about two hours. I had no problems any of the times and inflated the tires to about 70psi each time, well within the range specified. A week after the last ride I loaded my bike into the back of my Honda CRV. I didn't check the pressures at that time but they were obviously not flat. I ended up leaving the bike in the Honda for 4 or 5 days before finally unloading it. It became immediately apparent that both tires were completely flat. I took a look at one of the inner tubes and there was a four inch split at the seam that runs the full side of the tube. it was about 90-95 degrees on the days it was in the car and considerably hotter inside the car I would assume. based on the fact that the tires were aired up when put in the car and completely flat when I pulled it out days later I kinda assume it had to do with the heat. I'm just curious if other people have had this happen to them or if it might be something else I haven't considered. id appreciate any insight you have to offer
I have had a couple of times that an inner tube blew up while the bike was parked in bright sunlight. It seems that high temperatures are a contributing factor, but overpressure? I never pump my tires close to the maximum pressure, mostly the pressure is in the lower half of the min-max range. 

The pressure of compressed air increases proportionally to the absolute temperature, i.e. 273+T ;  T in degrees centigrade. Hence an increase from 95F (35°C) to, say, 140F (60°C) will result in an increase by only 8%. I don't believe this itself is causing the blow outs.

More likely the blow outs are due to an undersized inner tube in combination with a high temperature. Rubber is a material that behaves elastically in a limited range. Beyond a point it starts a plastic deformation. I guess that this point drops with higher temperatures. Most inner tubes are specified for a certain width range, e.g. 18&lt;-->23C for road bike clinchers. The remedy is to buy an inner tube that matches closely with the tire width.