Trailer Tire Replacement for Size A-78-13

Question:

I have a 1976 Ranger bass boat a real classic. The trailer has A-78-13 tires on 13in wheels, they are mounted with 5 lug bolts. I would like to go to st205/75R 14 in wheels. The center hub hole is smaller on the 13in rims than the 14in rims. It looks like the 5 hole pattern for the 13and14in rims are the same. I dont want to buy new rims and tires if they wont work. Will the lug bolts vs. Lug studs and nuts be a problem? And will the larger hub hole on the 14in rims be a problem? I would much appreciate your expertise... Thanks

asked by: Roger

Expert Reply:

Since your trailer uses lug bolts to secure the wheels to the hubs that means the hubs are hub-centric which means that the pilot hole of the wheel is what centers the wheel to the hub. To replace wheels you'd have to go with wheels that have the exact same pilot diameter as what you currently have so that it centers properly. We can help you replace just the tire though.

The metric equivalent of an A78-13 tire is a 175/80-13. This size is available in load range B, # AM1ST74, rated for 1,100 pounds at 35 psi.

It also comes in load range C, # AM1ST76 for bias ply or # AM10199 for radial, both rated for 1,360 pounds at 50 psi.

And there is also a load range D in this size, # AM1ST77, for bias ply and # AM10210 for a radial both rated for 1,610 pounds at 65 psi.

Radial tires run cooler and track better than bias ply tires but bias ply tires are better for off-road applications. I have included a link to our articles on tire sizes and trailer tires in general.