I recently purchase a new Exmark Lazer Z advantage series 52" ultracut deck. The front tires held air for about 2 weeks before one just went flat. I put air in it and it has been fine until yesterday. I took it off my trailer and then noticed it was flat again. This was the first time I had used it since last Saturday. I ended up using "old faithfull" (36 WB) on the yard I was at. I went to get air between jobs and it was flat before I got to the next yard, CURSES! Used the 36 again. Man, does it stink cutting with a 36 WB while I'm looking at a Lazer with 55 hrs on it on my trailer with a flat tire. For some reason this is one of the only models still using pnuematic tires - what's up with that.