I have an older Exmark Lazer Z 60" and I was wondering how much you can get out of a set of tires before replacing. I have a lot of hilly accounts that are safe enough to take this mower on, and I would like to have some good grip when on these hills. I probably have say 1/4-1/3" of tread left on these tires, and figure soon that I would need to replace them. How much remaining tread determines replacement? I was looking at the possibility of getting some different tires than what I have for next time(I have normal o.e.m. tires now). A mix between something that's better for the hills (something that grabs better), and something decent for the wet grass. Are the stock tires good enough, or is there something better out there? I do not want to spend big bucks on tires neither, so maybe sticking with the stock tires next time around would be fine by me. Any advice would be appreciated.