Here's my As other have said don't cheep out. I have an Enclosed (15,600lbs gross) that came with 225/85R15 E Good Year Marathons from the factory. Every 2 years a couple of them needed replacing due to belt failure. I switched to a 235/85R16 E Good Year Marathon and have not had a Belt failure since. Side wall deflection is typically the root cause for trailer tire failure. The E rated 16" has more belts and consequently a higher load rating and If I recall correctly they are (were) less expensive than the 15". My Big trailer (21600 Gross) has 235/85R16 Maxon 10ply (from the factory) and so far so good on wear and reliability. Point being more tire (load capacity) is cheaper in the long run.