What Replacement Tires do I Need for My A78-13 Boat Trailer Tires?

Published 03/11/2022

Question:

Hello, I need to replace the tires off my boat trailer. They are old tires, with the markings of A78-13. What is the modern equivalent size? Ive found varied information on line. From ST175/80-13, to 175/70-13 I think the difference is the overall size of the tire. The current tires come very close to the metal fenders. Are the new tires going to be too big and cause issues rubbing or even getting back on the trailer? OR am I going to have readjust my fenders? OR should I go with a car tire?

asked by: Sam S

Helpful Expert Reply:

The new equivalent of tire size A78-13 is 175/80-13. This is the exact same size, so there should not be any interference at all with your fenders that fit the A78-13. I went ahead and attached a FAQ article and table that shows this translation.

As far as using passenger car tires, we strongly do not recommend this for a couple reasons. Firstly trailer tires have stiffer sidewalls and do a better job dealing with vertical loads when hauling. Also, since trailers do not have turning axles, car tires have different cornering nuances than trailer tires.

For a great replacement tire for your boat trailer, I recommend the Kenda ST175/80D13 Bias Trailer Tire # AM1ST51.

expert reply by: Bob C