I use Steel Belted Radials on my 16' ProCraft's trailer ... 175/80R13 8ply Load Range D ... 65psi ... highway speed rated @ 65mph (boat weighs over 1700lbs alone, plus a 90HP Merc )
Both the Kenda's I had on there previously, and the Raniers I have on there now, list 65psi (*cold).
Most all the lakes I go to are a minimum 1.5hr trip each way, and most are Parkway or Interstate hwys for a good portion of the mileage.
I think the latest model Kenda tires of that size are listed at 70psi

