In order to replace the ST145/80-R12 tires on your trailer, I recommend using the Kenda Karrier S-Trail Radial Trailer Tire part # AM10140. This tire like your existing have a radial ply which is better for long highway hauls and it comes with a load range E rating which is suitable for use up to 1,520 lbs per tire. It also has a 65 mph speed rating.
In regards to the date code you can find this information on the sidewall of the tire. There will be a set of four numbers which are separated... view full answer...