Are you filling your tires with a regular tire pump, or a Co2 cartridge? If it's a Co2 cartridge, that is only temporary air and will leak out within a day or two. I went through a string of flats because I kept changing tubes and refilling out on the road with a Co2 cartridge. The next time I'd ride, I'd get a flat again. Finally I learned this most important tidbit of information and it solved all my problems! So, if you use Co2 out on the road, when you get home, let the air out and refill before you put your bike away. That way, when you go to ride again, if the tire is flat, you know it's not from the Co2 leaking out, but a real flat.