Ever since I've owned my bike, I've had a very difficult time inflating the tires. Today I needed to bring them up to spec, but I could not get any air to go into the tires. I could check the air pressure with a gauge just fine but no air would go into them. After trying various air chucks I ended up replacing the cores of the Schrader valves and was then able to inflate the tires. I've never encountered this problem on any vehicle. The valve cores did not look damaged but would not allow air to flow in only out.