I went for a ride four days ago. During the ride I can feel my rear tire (Continental Gatorskin tubular) getting soft. It is a slow leak but I can feel it getting really soft a mile later, so I stop, fill it with my co2 cartridge and ride home (another 20 minutes). Arrive home, tire is still hard.

Next morning, the tire is flat, so I change it.

Well, I want to find out what caused the flat on my tire, so I mount the tire to a spare wheel, pump it to 100 psi and listen for leak or try to feel where air is coming out. No luck. I rub soapy water on tread. Still no leak. Two days later the tire is still pumped up hard as a rock.

So how can a tire go flat (twice) then stay filled like nothing ever happened?