I have a 2004 Metro HP 36" with the 15 Horse KAW that has lately been leaving tire ruts in my mowing pattern. Not divots from turning, but in the normal path of mowing on each side of the swath. I use the mower primarily to access back yards with gates and to mow small town home size yards. I am 6'2, 225lbs and ride a jungle jim velke behind this mower. However, I tried walking instead of standing on the velke and it continues to make the ruts. I have checked and played around with tire pressures, both lower and higher; maintain a sharp edge on both cutting blades, which are brand new and have been used maybe twice; and, have checked the blade height and pitch of the deck, which is neutral, meaning equal height in front and back. I mow at 3.5" and alternate the mowing pattern every other week, i.e. one week straight, next week diagonal. I do have a set of new tires for this mower, but they are not installed. Would this help? Any other suggestions or thoughts on what i might be overlooking would be appreciated. Thanks guys.