Trailer tires

We bought this 5er a year ago and the first owner had a blowout with the original carlisles and he put them on again. They are about 3-3.5 years old according to the invoice but get this... there are no numbers molded in any of the ovals. I don't know how that happened! Anyway, they look perfect when I spin them. The towmasters I've had were crooked and had ripples in the sides. I don't care how good these carlisles look, I'm putting on LTs before going very far. 4 yrs is a little too long on STs, here.Craig