I have run into a problem with my 318 and its rear tires. When I bought the tractor, I noticed a leak in the right rear tire. It was slow and I had to add air about twice a month. So I just lived with it. I noticed the the leak was getting worse. When I decided to fix it, I found a hole in the tread that was minor, so I tried to break the bead but could not. I took it to a tire shop and they patched the tire for me. When I got home the tire would still go soft. I checked and the leak was around the rim both on the inner and outer rim. I took it back to the tire person and they tried again and told me that the rim or the tire was bad. It still leaks. The rim does not look bad, nor does the tire. I have never had to replace either a tire or rim on any of my tractors before. Do these rims have a problem with sealing tires? Is the best option to put a tube in the tire? Size is 23 x 10.5 x 12.