About 3 miles from home last night I noticed a bumping from my back wheel and quick inspection revealed a grape sized blister on the rear tyre. At the time I guessed the tube had pushed through the carcass and decided to limp on and sort it at home. About 300m down the road there was a loud bang but, oddly, no flat tyre. The blister had burst but that was it. I've yet to inspect but the only scenario I can come up with is that the 20psi I've been losing each day has left the tube but not the tyre - That the tyre itself has become pressurised. Anyone had a similar experience? All will, hopefully, be revealed when I get up close and personal with it tomorrow morning.