What size and type are our horse trailer tires?

Question

On the side of our horse trailer tires it states: Dico st, Sport Trax, F78 15ST but no where does it state the size.

Answer 1

F78  15 IS a tire size.  the tires are Bias ply tires not Radial.  Any tire shop can tell you a comparable radial size

Answer 2

The F78-15ST trailer tire is also called an ST205/75D15.

Answer 3

The answers above are correct but I dont see why you would have an (F) series tire, those are very old and unsafe tires.