I have a B6000 and had the same problem. I had ag tires 6-12 on front and 7-16 on rear. I put carlisle turf 22x7.50-12 on front I bought from smallenginewarehouse.com for less than $75.00 shipped for both. Any passenger car or light truck tire 245/70/16 for the rear will work fine. I also think the firestone winterforce tire is the best choice, they are directional with soft rubber to grip the grass better and they are the most cost effective of any new tire. I have spent many many hours researching this. You will not be dissappointed. I am not sure if they will hold air without a tube because I kept the tubes in mine.