tire pressure for a 13' 20lb max?

[floyd]

Originally Posted by Wayne Collins

The problem is that load/inflation tables are not supplied with each tire.
You have to go to the manufacturer's catalog spec sheets, or the Tire And Rim Associations hand book to find them.
Regardless, you are not required to use the max pressure shown on the tires .... unless they are carrying the max load.

And you should never go to by the minimum pressure/load chart unless you want catastrophic tire failure.

[Donna D.]

Originally Posted by Glenn Baglo

The information on the decal applied to the tires that were on the Scamp forty years ago.

Tires have changed a LOT in forty years. Read the info on the sidewall. The tire manufacturer is the "expert" for their product.

[Steve L.]

Generally, if someone doesn't know what their trailer weighs I suggest spec-ing the pressure at the axle GAWR/2. Admittedly this ignores the possibility that the trailer is overloaded for even the axle to carry. I have no sense of how often that happens but I'm convinced that people without an actual measured weight are usually running heavier than their estimate. I wouldn't suggest using any tire that can't carry at least the axle GAWR/2 just on principle.

Car tire pressures are determined by more than the weight of the vehicle. Handling, braking and fuel economy are among the other factors determining the recommended pressure. Using car weight as some sort of predictor of trailer pressure is wrong.

The load tables for ST and LT do not depend on brand so any vendor's load table will work for the same size tire of another brand. I've gone ahead and included the chart for common ST tires.

ST and LT tires carry less load per PSI than a P-metric or R-metric (European pass car tire) or, put differently, they require more inflation to carry the same load. Less deflection means statistically fewer road hazard failures. This is another reason why comparing car tire pressures to ST/LT tire pressures is just wrong.

I have no issue with running at load table recommended inflation so long as pressure is checked (cold) before every trip. Checking pressures is a good idea regardless. Nor do I have an issue running at the max pressure on the tire sidewall.

I don't recommend passenger car tires for trailer use, not even considering the 10% load reduction Tire and Rim (and the government) specify for P tires on trailer applications.

[Cathi]

We have Carlisle trailer tires. Carlisle info says to put their trailer tires at the maximum of 50. That is what we stay near.

[Casita Greg]

With all this talk about various tires/pressures, etc., the one thing missing in all these posts is that not only is all the older tire data from bygone ages outdated and inaccurate, relative to modern standards and tire specifications, but let's not forget about the wheel rims themselves. Most older rims were not constructed to meet the pressure demands of the newer higher pressure tires manufactured today. Many older rims are not capable of handling increased pressures. It's not all about tires and tire pressure. Rims also have limitations on pressure as well. If you are considering upgrading your tires, consider upgrading your rims as well.

[floyd]

Originally Posted by Casita Greg

With all this talk about various tires/pressures, etc., the one thing missing in all these posts is that not only is all the older tire data from bygone ages outdated and inaccurate, relative to modern standards and tire specifications, but let's not forget about the wheel rims themselves. Most older rims were not constructed to meet the pressure demands of the newer higher pressure tires manufactured today. Many older rims are not capable of handling increased pressures. It's not all about tires and tire pressure. Rims also have limitations on pressure as well. If you are considering upgrading your tires, consider upgrading your rims as well.

Just curious, have you ever seen a 13" trailer wheel which failed from over pressure?

[Glenn Baglo]

After picking the shrapnel out of your eyes, there's not much to see.
But, rims are rated for max tire pressure.

[Borrego Dave]

Originally Posted by floyd

Just curious, have you ever seen a 13" trailer wheel which failed from over pressure?

Can't say that I have but at 50# I don't see that that would be a problem even for older rims. I think rust would be a better bet for a failure especially on the bead, maybe from road salts ect. I've had a rim or two on my dune buggy not hold air to well after many water "drownings", even with cleaning them to bare metal and new paint.

[floyd]

Originally Posted by Borrego Dave

Can't say that I have but at 50# I don't see that that would be a problem even for older rims. I think rust would be a better bet for a failure especially on the bead, maybe from road salts ect. I've had a rim or two on my dune buggy not hold air to well after many water "drownings", even with cleaning them to bare metal and new paint.

[ShelbyM]

Casita gives an opinion for the OEM Goodyears, Goodyear have their own weight/pressure table and Carlisle unequivocally state we should use the max pressure on their ST tires. If you upgrade to the newest Carlisle HD, they are E rated, 80psi. Not to mention rims....

[Civilguy]

Originally Posted by Raspy

Softer tires have better tracking on rough surfaces and better traction on icy roads, but may sway more at speed.

So, we don't get a lot of snow in my area. One morning some 30 years or so back, we had six inches or so. I had an old 1/2 ton Dodge van with some radial tires, and likely inexpensive ones at that. Those were definitely the "spaghetti days".

I had some significant hills between my home and my workplace but needed to get there.

Not having any chains to fit the van, I recalled one time at Pismo Beach when we had taken our tires down to about 10 psi in an old Land Cruiser. It worked like a charm on the soft dry sand on the dunes. We could go places in 2WD that we could not go in 4WD with full tire pressure.

So, I brightly took the van's tires down to a much lower pressure. Following a little test drive with alarming results, I was then treated to an exercise in inflating them back up to recommended pressure with a hand pump. There was an awful lot of air to be added to those big tires...

Next, I took some NM cable (Romex style) and found I had just enough cable to get four wraps around each rear tire. That sufficed to get me to work. By the time I needed to drive home, the bare pavement chewed up the Romex and I pulled it off on the way home.

So, I have since made it an article of faith to make sure that our car tires are fully inflated during the winter, a few psi above the vehicle's half load pressure noted inside the gas cap. This means about 32 psi versus 28 psi as recommended for half load in the case of our 2003 Passat. I figure the tire pressures are not going to elevate as much while driving in the cold weather as they do during hot weather.

So, am I correct in believing that low pressure is actually not good on snowy / icy roads? I expect most folks have more experience with snow and ice than we get in our area.

[floyd]

Originally Posted by Civilguy

So, am I correct in believing that low pressure is actually not good on snowy / icy roads? I expect most folks have more experience with snow and ice than we get in our area.

On road traction in snow actually works best with narrower tires with aggressive tread. We often see that 4WD trucks with wide offroad tires can not come close to competing with stock sized properly inflated tires on a stock truck.
On beach sand there is a need to float with wide tires at low pressure.
On snow covered paved roads there is a need to cut through the snow to gain traction.
I was driving home in my Pinto one day in deep snow. The snow packed into the timing belt and shifted it, shutting down all progress.
Along came a 4WD farm truck with relatively narrow stock sized stiff tires. He hooked a chain onto my car and towed me the last 5 miles to my house. On the way we had to drive through a ditch to get around a JD4020 with a snow plow which was stuck in the middle of the road.
Trying to float on snow with tires too wide or under inflated, can cause a loss of control or even a roll over. (Save that for snowmobiles.)
As for a trailer, it will go where it is "towed" when equipped with right sized tires properly inflated.

[Civilguy]

Thanks Floyd!

We can now return our readers to our regularly-recurring thread on trailer tire pressures.

[Mike Magee]

Back to the OP, I would get rid of that lousy sticker in the wheel well that says 20 Lbs Max. With today's tires, 20 Lbs. Min. would be a much better (but far from perfect) rule of thumb.

[Raspy]

Originally Posted by Civilguy

So, am I correct in believing that low pressure is actually not good on snowy / icy roads? I expect most folks have more experience with snow and ice than we get in our area.

Lower pressure works well on snowy roads. But not way down like you do in sand.

On icy highways the ice becomes rough. Hard tires tend to skate around on this surface because they cannot conform to the irregular surface if they have highway pressure. Traction suffers with high pressure on paved surfaces that are frozen with ice and you can find yourself sideways pretty easily.

The second situation is deeper snow. If tires are too hard to flex much, they will pack up and become smooth as though they have no tread. Then traction is very poor. Flexible tires with less pressure will flex and throw out the snow from the tread. They clean themselves. Then deep clear tread is constantly coming in contact with the surface.

In both cases the object is to engage the surface and not just pass over it.

Narrower harder tires with very aggressive tread can act like gears in muddy snow and get ahold of a lot of material to pull themselves along by getting deeper into the surface and not floating on top of it.

Running in sand like you'd find at the beach, the wider the better for floatation and the lower the pressure the better, within reason. Sand also works best with speed and power. More speed and more power solve traction issues in sand. I have a set of soft wide flotation tires and a set of narrow hard "pizza cutters" for my Jeep. The soft tires will go places in sand, in 2WD, that the narrow ones can barely do in 4WD.

In the desert with sandy roads with rocks, ruts and pot holes, definitely air down to about half normal pressure. This takes a lot of stress out of the suspension and adds a lot of traction. Plus it reduces the chance of destroying a tire on a sharp rock.

On my Ram, with load range E tires, I tend to let them down from about 60 PSI to about 40 PSI in the snow on the highway. This makes a big difference, but isn't so low that I might damage a wheel or pinch the sidewall. Also, since they are not then skating around on a hard uneven surface, the ride improves. They also don't get hot in that kind of weather and running at slow speeds, but I'll drive them in dry conditions to get to a convenient place to air back up.

[Civilguy]

Thanks John! Who knows, I may just learn something someday.

Pumping up all four tires on that old Dodge van with a bicycle pump was certainly an education!

[floyd]

Originally Posted by ShelbyM

Casita gives an opinion for the OEM Goodyears, Goodyear have their own weight/pressure table and Carlisle unequivocally state we should use the max pressure on their ST tires. If you upgrade to the newest Carlisle HD, they are E rated, 80psi. Not to mention rims....

Goodyear's Weight/Pressure tables which apply to RV trailer tires clearly state that they are minimums to prevent tire damage. It is in their PDF on their website.
Goodyear even recommends removing the tire from the rim to inspect for damage if they are run at pressures below the chart.

[ShelbyM]

Originally Posted by floyd

Goodyear's Weight/Pressure tables which apply to RV trailer tires clearly state that they are minimums to prevent tire damage. It is in their PDF on their website.
Goodyear even recommends removing the tire from the rim to inspect for damage if they are run at pressures below the chart.

Yes, that's my point, sorry if I was unclear Goodyear gives you the option to run lower than max pressure, using their weight table. Carlisle says always use max pressure. I guess if you run Goodyears you can weigh your trailer and select an appropriate pressure. If you run Carlisles you just pump 'em up and go....???

[floyd]

Originally Posted by ShelbyM

Yes, that's my point, sorry if I was unclear Goodyear gives you the option to run lower than max pressure, using their weight table. Carlisle says always use max pressure. I guess if you run Goodyears you can weigh your trailer and select an appropriate pressure. If you run Carlisles you just pump 'em up and go....???

Your point is not really the same as mine...
Of course if you wish to run a few pounds lower than maximum tire pressure on less than a maximum load, you can do so safely. As you approach the weight table limits you will increase the possibility of uneven tire wear and the danger of catastrophic failure.
It is better to get the right tire for the trailer to begin with, but good "B" rated tires are hard to find nowadays for lighter trailers.
The maximum pressure which will still allow even tread wear is most efficient and safest for a trailer tire.
The best trailer tire wear and longevity on my Scamp13 has been Carlisle RH with 50PSI. My present spare was taken out of service in good condition with even wear and more than 30000 miles on it, leaving about 40% tread.
When I bought my trailer, it came with "B" rated Marathons (35PSI Max on sidewall). I ran them 27000miles @ 40PSI before switching to "C" rated tires which I felt were more appropriate for my application.

I am presently running my second set of Carlisles and...
Yes, I "just pump 'em up and go".

[ShelbyM]

Well, I guess I don't get your point. Are you using Carlisles and running a pressure other than what they specify (max on sidewall?)