New Tires - What PSI?

[tewfiks]

Hello All:
We are finally going to use our new to us 1978 AS Sovereign 31' Land Yacht. It is mostly original with the exception of the refrigerator. We are planning on gutting it and updating to our likes, but for now it is going into service. The kids want to go to Mount Rushmore at the end of the month. I began inspecting it for our journey and noticed cracks in all four tires. I replaced them with E rated trailer tires. My question is do I run them at 80 psi or at 65 psi?

Thanks for any help. I am anticipating many opportunities to learn on this trip.

[FCStreamer]

What do the tire sidewalls say?

[SpletKay06]

Start at 80 if it rides to rough try 65

[tewfiks]

The side wall reads:
E load rating and 80 psi max

[TG Twinkie]

I would run 65, you are nowhere near the max load capacity of 4 E rated tires. No point in beating your coach to death especially if it has the original axles.

[xrvr]

When in doubt use the max.

[CapriRacer]

What we have here is a situation where the vehicle had one size tire on it when it was produced, and the tires have been replaced with another size from a different sizing system. It would be nice if we knew more about the original tires and what the vehicle tire placard says.

But if that info is not available, it is likely that 65 psi a good guess - and I would suggest followup monitoring: Check the pressure buildup during an extended high speed run - and hour or more. If the pressure build up is less than 10%, that would be good. If it is more than 10%, you need more pressure and if it is more than 15%, you need to take immediate action - like slowing down and adding air right now!

[joel]

I ran 65 on my 86 32 . I run 70 on my 90 32 start at 65 if the trailer tends to say it's tail and sway and it is hooked up correctly with anti sway hitch go up about 5 lbs .that stopped the little bit of sway that was left in mine.

[Action]

Dry weight ranges from 4700 to 4800 pounds

Depending on how you travel with tank levels, loaded weight could be 1000 to 2000 pounds more.

Actual weight would be best measured on a scale so at least you have a reference and can add or subtract as you travel or restore.

>>>>>>>>>>Action

[TomKirk]

Side wall PSI says one thing. Owner's manual says another. Which is correct??

The owner's manual for my '77 Sovereign says 45 PSI.

Stick with the owner's manual.

Tom

[Action]

Side wall would be max pressure for max load on a cold tire.

>>>>>>>>>>>>Action

[PecanMan5]

I start at 65 cold and let them warm to 70.

[IAMGLG]

What is relevant is that you put pressure monitors on the metal valve stems. You don't want an unrecognized blowout: then put 65 # in them.

[m.hony]

I have 65 psi cold per the placard on the side of the trailer.
When I am underway the pressure increases to 70-72 psi due to heat while rolling.

[Action]

There is no relevant specification for air pressure to be changed on a warm or hot tire.

One may observe pressure on a hot tire. Changing tire pressure on a hot tire is foolish as there is no specification for pressure on a hot tire that I a aware of.

>>>>>>>>>>>Action

[larryglarson]

65 PSI and watch tire ware.

[Phoenix]

I think I remember reading several years ago where someone said that if higher tire pressures (65 & 80 psi) were used on the old wheels on vintage Airstreams, the rims could crack at the bead and cause the wheel to fail.

Does anyone else remember reading something to that effect?

[Sisu]

The pressure on the tire sidewall is the maximum cold inflation pressure.
Most tire manufacturers will provide, on their website, a chart with cold inflation pressures for the specific tire model by tire size and the weight that the tire is carrying. This is best determined, as someone mentioned above, by weighing your trailer as you typically load it.

[guskmg]

Watch out for old alloy wheels, paticulary the oval shaped slotted wheels, Westerns, made by North American used in the 80s. They are excellant wheels, but they are only rated for "D" range at 65psi. I have cracked them with 80psi "Es." If it is hard to find a slow leak, look for a cracked rim usually running around the rim just under the bead lip.
guskmg

[aftermath]

Originally Posted by tewfiks

Hello All:
We are finally going to use our new to us 1978 AS Sovereign 31' Land Yacht. It is mostly original with the exception of the refrigerator. We are planning on gutting it and updating to our likes, but for now it is going into service. The kids want to go to Mount Rushmore at the end of the month. I began inspecting it for our journey and noticed cracks in all four tires. I replaced them with E rated trailer tires. My question is do I run them at 80 psi or at 65 psi?

Thanks for any help. I am anticipating many opportunities to learn on this trip.

When you replaced the tires with E rated tires did the installer check to see if your rims can handle the increased pressure? If not, you might want to go back and have them check.

To do this correctly you really do need to know the weight of your trailer. I use the GVW posted on and in the trailer. Once you know that, take the weight rating for your E tire and multiply it by 4 to see the load carrying capacity of the tires. You should be well over the GVW of the trailer and that is a good thing.

Inflating cold to 80 psi will provide the maximum for each tire. You can run less but that will diminish the amount each tire can carry. There is a chart out there somewhere that shows how this works. The tires should always be able to carry more than the weight of your trailer. I like to be at least 15% over.

It makes little sense to me to follow the instructions on the side of your trailer if you have changed out the tires to something quite different from the originals. And, proper inflation is important, more so than having a nice TPM system installed.

If you google Maxxi tires, you should be able to find the chart I talked about. Hopefully someone will chime in with a link. And make sure your tires are balanced. Years ago I put some new tires on my tent trailer and the guy told me that they generally don't balance tires on small trailers. He went on to say they don't do it on boat trailers either. I told him that they were going to do it on my trailer and they did grudgingly and I never went back.