I had an interesting situation with my new SD60. After cutting grass for the first time and "playing" with my new ZTR for a week or so, I discovered a completely flat left front castor tire. I checked all the tires for proper air pressure and found the right front had about 8 PSI in it. The max listed on the tire was 28 PSI. I put 8 PSI back into the Left , assuming the dealer knew the correct PSI needed. I also had read that less PSI would result in a better cutting ride on the SD 60. The tire went flat again in about a day. I was upset to think about dealing with Warranty work already. I then put 20 PSI in both front tires. The left lost air pressure again and was down to about 12 PSI by the next day. I refilled it and was calling about the warranty repair with the dealer. The tire has now remained at 20 PSI now for over a month. All I can figure is that the tire never had enough initial pressure to "seal" the bead properly on the wheel. Maybe someone here has an answer that makes better sense or that has experienced a similar situation. I love my new SD 60 and look forward to many years with it.