Originally Posted by
sharp
... I run my fingers up and down over and over inside my tires to feel for anything until I'm sure there's nothing. Then I visually inspect the outside to see if there's anything stuck in that I couldn't feel from the inside...
It is possible to have crap in your tires (usually tiny shards of glass or wires picked up from the road) that you can't feel or see, but that are still in there. Are you flatting in different places on the tube/tire? If so, you're just experiencing bad luck. If you don't know, you should always keep track of where the leak is by paying attention to the orientation of the tire and the tube.