The snow is finally gone here. I got out the NT to take a ride for the first time since October and the front tire was flat. I aired it up and when I checked it ten minutes later it was flat. Aired it up again and checked for leaks. Couldn't find any. It went flat again. Aired up again this time 40 pounds. Checked for leaks slowly with soap and water. None found. Checked several times over two hours. No pressure loss. Rode bike 76 miles. No air loss. What happened. Was tire maybe loose from rim and resealed when I put in extra pressure, just a guess. Tires are pilot road 4's with a little over 4000 miles.