At the risk of repeating myself, I will mention this again. Most tire dealers, at least honest tire dealers, will tell you that 4 years is pushing the life of trailer tires. In Arizona 3 is closer to being replacement time. The long spells of sitting, the turning and backing without a differential puts major strain on the tire and tires sidewalls. Most sit for days, weeks and months in the elements, including sun which dry rots rubber, as well as other products. There will be those that tell you they have gone 5 or more years with the same tires. Good for them but that length of time is asking for a failure and possible major damage to your unit, not to mention the safety of you and others on the road. So, while the tread looks great at 4 years, there are probably hidden issues with the tire that will jump up and get you sooner or later.
