Tire psi

You bet..... especially internal dry rot that many times can't be seen by looking on the inside or outside of the tire. I've used dozens of bias ply tires on my GN trailers years ago when I hauled for a living. They do run hotter than a comparable radial tire. If it were my choice they would be replaced with a quality tire before a trip.

The last letter designation tire I had that came on a trailer was a bias ply H78-15 6 ply rated on a 1984 5th wheel Aljo by Skyline.

@jimnlin....actually I would assume the tires are vintage 1989's. The camper was used very little over the years by a fire company for fire saftey demos.Tire treads pretty much in tact. As far as how they stand up all these years later....did concern me. Not sure if unused, or used very little the tire still would have aging affects of the years?

cs2kplus wrote:
Have 4 tires on trailer. They are:

f78-15st st205/75d15

PSI max is 50.

What is recommended for towing? Max or under? I did 45.

They haven't made a F78 tire in years. I wouldn't plan on any all day long trips at interstate speeds on those old timers.
Max pressures will keep them the coolest running.

Executive wrote:
Max as stamped on the sidewall. Check your rims for max psi also. Most ST tires are speed rated at 65mph...Dennis

@Turtle...You're from California so I know you NEVER exceed 55mph..:W....D

Believe it or not you're 100% correct. But I LOVE Utah so I visit there as often as I can and those people "roll" in that state! 80 MPH speed limit in a Corvette, big rig or anything inbetween; it doesn't matter, so, when in Utah................ :W 55 till the border baby and then hammer down......

Max as stamped on the sidewall. Check your rims for max psi also. Most ST tires are speed rated at 65mph...Dennis

@Turtle...You're from California so I know you NEVER exceed 55mph..:W....D

I've got the same size tires and always run them at the max, 50 psi.

Dakota98 wrote:
If you use Nitrogen, your fuel mileage will double. :B

OH MAN LETS NOT START THAT******AGAIN LMAO

cs2kplus wrote:
Have 4 tires on trailer. They are:

f78-15st st205/75d15

PSI max is 50.

What is recommended for towing? Max or under? I did 45.

Depends on the weight being carried, 15" ST's are usually at Max weight capacity, so Max sidewall pressure.

The correct way is to weight the weight carried, if well below the tires capacity then adjust down to keep traction.

If you use Nitrogen, your fuel mileage will double. :B

I always tow at max pressure and most of the time max pressure +10 PSI because I run fast. Pressure is your friend to keep heat down.

One blow out in 40 years RVing. I think that was a nail.