Carlisle Tire & Wheel Company
Bias Line
Carlisle Tire & Wheel Company
Radial Line
Carlisle Tire & Wheel Company
Bias - a guess the last one in this list may be what you have.
You can match up the sizes and deduct if you have one of these three lines or another.
On that trailer only a E (LRE) load rating is going to give any margin of safety if you are going to fully load it. I expect that only radials will go that high based on these charts. This will give you around 3000 pounds of load rating per tire.
Read on your tires what the load rating is in POUNDS. Hopeful at 65 PSI they are good for 2500 pounds. Technically four would give you 10K gross capacity BUT they will not provide the protection against blow out and other problems that a E rated tire that would be good for more like 3000 pounds each.
If you will buy a new set of E rated (3000 pounds) of most any brand of radial tires and put them on the front axle AND your hitch height permits you to tow with the trailer level you will be in good shape. When you replace the current ones get the same your two new ones IF they have given you good service.
There is no way on God's green earth for a man to load a twin axle trailer with a gross of 10K pounds and have 2500 on each tire.
This is why the 80% rule is provided by the tire experts.
As a rule any tire on any equipment hauling trailer with < Load Rating of "E" will leave a bad taste in your mouth. In the case of RV's it is even more critical due to the $$$$ of damage a blowout can cause to the RV itself.
Look at the LRE tires in the charts where the last letter denotes load rating. See their weight and tread thickness. Just in tread you get 30% more so that offsets some of the higher cost because of longer tread life.
Do not fret over what you may not have but just know if you fully load the trailer with less than E rated tires from any brand you choose the will be trouble so just back off with the load you put on it.
Hint 1: At some point you will be tempted to over gross your trailer.
Hint 2: There is NOTHING cheap about low quality tires. Quality only cost ONCE but it up front.
Get you a set of E or better (watch rim PSI limits when hitting F or above tires for anything) and get to trucking.
Shop because I got Carlise UT tires C rated for much less than for B rated by shopping. Find you a small tire store managed by the owner and talk with him or her.
Consider Greenball based on Chris' personal experience and business experience. Just so not overload what you currently own.