Max PSI

[Ag&Au]

Originally Posted by purman

That just gives you the max PSI, What people need to know is what PSI for what weight. Just because you can put 65 psi in your tires doesn't mean you should..

People don't run the max PSI on their car or truck? So why run the max on a AS. Run what your weight is plus some for extra cargo. When towing I up my PSI on my SUV by 10 psi to 55 psi. front and back. I can go up to 80 psi but don't need to. MY trailer (originally) was 4800# dry. Now i'm betting its over 5000# plus everything else I'm up around 6000+. I don't need to run my Trailer up to 80 psi, It will just bounce down the road...

Read it more closely. It give maximum load for a given PSI. So if you read it the other way, It give the minimum PSI for a given load.

Ken

[perryg114]

Well how about everyone start measuring tire temperature profiles at different pressures and see what you get, myself included. I expect I am running my tow vehicle tires at too high of a pressure and the wear patterns on the tires I just took off support that. Another way to determine proper pressure is using the chalk test. Put a chalk mark on the tire and drive a few feet. If the mark is more faded in the center then too much air if on the sides then too little. The temperature test is better.

Perry

[3campers]

I guess it directly relates to your situation and set up. I run my AS tires at 50 each and my TV (E rated) tires are 50 up front and 60 in the back. For me the ride is super smooth. I have to remember to knock the rears to 50 when I done or my truck rides like a tank!

[slowmover]

Trailer tires at maximum sidewall pressure. No exceptions.

Tow vehicle:

1] Within vehicle manufacturer placarded limits
2] Also respecting any FF/RR bias

Load versus pressure for the TV. After 1.5 hours of steady state driving, should not see more than a 3-5 psi pressure rise (from cold). The "lowest" air pressure (respecting the above) with this low pressure rise is the number to try to achieve for best handling, braking and tire life. A few more pounds (respective of percentage change) for slightly better mpg, perhaps. On the rollover prone pickups/SUV's this is even more important.

You all might read around on BARRY's TIRE TECH website, by a tire engineer who has recently taken an interest in RV tires (especially the problematic ST). The above is just a condensation of that, and from the RV.net thread "Revised" from a little earlier this year.

A quality tire pressure gauge, a trip or two to the scales (not just for hitch rigging), and some record keeping to know the TV tire pressure range from solo/unladen to solo/laden and to the highest wheel position weights when towing.

.

[TG Twinkie]

Our 26' Argosy has a GVWR of 6200#. I have run 3 years and almost 20K miles with the pressure at 55#. Haven't had a single tire problem. No rivets popping etc..
Have left items on the counters by accident. They are still there upon arrival. Towing speed is about 62 mph.
Never run the E rated tires on the TV over 65#.
I check the pressure in the morning before departing and about once every 600 miles or so.
When I stop for fuel or at a rest area, I check for hot spindles and wheels (for brakes running hot) and give the tires a kick.
Been doing this for the last 51 years of driving, pulling every kind of trailer one can imagine with every kind of load as well.
Although I haven't kept track. I'll bet I haven't had to change more than 1 tire every 5 years. I would bet that 80% of those flats were caused by junk on the road.
Maybe I'm one of the lucky ones. Don't know.

[macofpei]

So, If I currently have D rated tires--@ 65 psi and now I am thinking of changeing to an E rated tire, can I still run at 65 psi or do I have to increase to the 80 psi--I ran my tires (last falls trip) at 60 and had a blow-out. All other trips I took, I was running at 50 psi. It would seem to me that when I added the extra 10 lbs of pressure, my AS bounced more that it did at the 50. I have a 30 Classic rated @ 8700 lbs.

[purman]

Originally Posted by macofpei

So, If I currently have D rated tires--@ 65 psi and now I am thinking of changeing to an E rated tire, can I still run at 65 psi or do I have to increase to the 80 psi--I ran my tires (last falls trip) at 60 and had a blow-out. All other trips I took, I was running at 50 psi. It would seem to me that when I added the extra 10 lbs of pressure, my AS bounced more that it did at the 50. I have a 30 Classic rated @ 8700 lbs.

D rated tires have a load of 2540# I believe. If your running tandem the total load for all four is a little less say around 9000#. I need to find the chart to be sure.

My tires have a load capacity of 2680# but on a dually trailer they have a load of 4470# They are E rated Michelins... 225 75 R16

So you should be running pretty much max psi of 65 or 60 psi on your tires because you are pretty close to you max rating on your tires.

I ran 60 psi on my D rated Carlisle tires and my trailer is under 7500 lbs loaded..
Goggle your tires chart on line to find the exact load range for 4 tires.

So to answer your question "YES" you can run lower than 80 psi. But the Michelin chart for my tires says 65 psi would be less than what they want for your trailer weight. 70 psi would be recommended. But you need to consider what you have in the trailer. Dry weight is different the loaded weight..

Whatever tire you switch to, look at the weight ratings for that tire and what minimum psi you can run at that weight..

Good luck, this is a hot topic...

[slowmover]

The pressure/load range tables are not for trailers.

There is a reason ST tires are marketed as having "stiffer sidewalls", and the reason is the forces trailer tires undergo which passenger vehicles do not. The trailer is levered -- jacked -- into positions, and not just in backing. Turns, again, leveraged by the tow vehicle exert pressures against the trailer which passenger vehicles do not undergo.

The "best" tire has much to do with matching the load of the trailer, yes, but the sidewall printed maximum pressure is a requirement for trailers.

Go read your owners manuals.

Or tell us why more than one tire engineer is wrong on this subject.

.

[perryg114]

I seem to remember this statement at the beggining of his ST tire page.

First, this article is about travel trailers – RV’s – that have ST type tires. Other kinds of trailers or RV trailers with other types of tires are not addressed here.


If tire engineers are so godly why are so many ST tires failing? There are good and bad engineers and those bogged down in corporate BS and bureaucracy to do their jobs. So brand me a heretic. Following the status quo is not working and tires are failing. When ST tires are tested to the same standard of car tires I will start using them.

Perry

[purman]

Originally Posted by perryg114

I seem to remember this statement at the beggining of his ST tire page.

First, this article is about travel trailers – RV’s – that have ST type tires. Other kinds of trailers or RV trailers with other types of tires are not addressed here.


If tire engineers are so godly why are so many ST tires failing? There are good and bad engineers and those bogged down in corporate BS and bureaucracy to do their jobs. So brand me a heretic. Following the status quo is not working and tires are failing. When ST tires are tested to the same standard of car tires I will start using them.

Perry

I'm with you.

[bovk]

I will be talking about a single axle trailer only. The reason I stated that is that the need for ST tires is 0 (if you see a reason please respond).
We got so scared of blow-outs that we measure slightest differences in temperature, pressure, load and so on. That is the result of a badly designed tires from more than one manufacturer. If a tread separates at one set of conditions it will separate within all of conditions I read in this thread. If you choose a well designed tire rated for your use it will serve as well as if it would be installed at the rear of your TV, meaning 50kMI plus. What tire you choose is a subject of a different thread but for single axle LT tire 16", rated E is a good option.
With this in mind, I think 70 psig on the E rated tires (it drops the rating to D) is OK, I am watching mine for the last 4000 MI trip and I do not see any negative effect, they are colder compared to my TV tires (the same brand, type, size).

[slowmover]

Originally Posted by purman

I'm with you.

I sure you both misread the post. The thread is about max psi on tires, not ST tires. Try again.

[purman]

Originally Posted by REDNAX

The pressure/load range tables are not for trailers.

There is a reason ST tires are marketed as having "stiffer sidewalls",

.

No Where on my ST tires does it say it has a stiffer sidewall.. how is it made stiffer? It sure doesn't have anymore belts in it. and plenty of people have busted ST tires parking their trailers. So if they do have stiffer sidewalls it isn't doing much..

Max PSI is just that. The MAX, it doesn't mean you have to run the MAX, I never have and never had a blow out. I sure don't run the Max on my TV.. And the Max weight of my ST tires was far above the weight of my trailer. So why would I run them at the Max if my Weight was nowhere near the Max. Just makes for a rough ride.

thats a lot of MAX

[perryg114]

If you take any tire at 80psi it will be a lot stiffer than at 50psi.

Perry

[purman]

OK, I don't think this will ever be settled. But I searched most of the tire company web sites and couldn't find to much info on putting your tires to max PSI.

What I did find was plenty of PEOPLE, NOT tire companies saying you should.

No it can't hurt a regular utility trailer or boat trailer to do this. But we are talking about AS and they want a smooth ride, not a bumpy one, and thats what MAX psi will do if the max weight rating of the tires is well over what the MAX weight of your trailer.

This is from the Goodyear website: (RV section on tires)

Proper Tire Inflation

Correct tire inflation is a key component in tire care. The recommended maximum inflation pressures for your tires are indicated on the certification label or in your owner's manual. Since RVs can be loaded with many different configurations, the load on each tire will vary. For this reason, actual air pressure required should be determined based on the load on each individual tire. Inflation pressure should be adjusted to handle the tire carrying the heaviest load, and all tires on the axle should be adjusted to this standard.
Each manufacturer provides load and inflation tables specific to their products to help you determine the correct tire inflation pressure for your vehicle's loading.
Underinflation brings a higher risk of susceptibility to damage due to road hazards, reduces casing durability, and causes a loss in fuel economy, plus uneven or irregular tire wear. Severe or prolonged underinflation brings about an increased risk of tread separation.

So, what ever you do don't under inflate your tires. But also don't over inflate them..

I don't think we will ever get a straight answer on this, even from the Tire industry..

My tires are rated to 9800 lbs, my trialer loaded is well under 2500 lbs of this. So I don't see the reason to run the max of 80 psi. It will give a harsher ride than is needed, and bounce the inside of my vintage AS. I'm I going to run 55 psi? NOPE. This is not an ST tire anymore either. I will run between 63-and 73 psi. I will have to play with it to see where the temps run the coolest, and the ride is the best.. IMO..

[Ag&Au]

Originally Posted by purman

I don't think we will ever get a straight answer on this, even from the Tire industry..

.

You will not get an answer from them because they don't recommend truck tires on trailers. Until they do you will have to use whatever information you can find if you put LT tires on your trailer. You and only you have to live with what you choose. There are other who choose to do differently. They have to live with their decision also. You can't expect an company to spend money on research on how to use their product in a way they don't recommend.

Personally I am going to inflate mine to the max, because I'm pretty close to that anyway, and I believe that's the safest.

When my stiff suspension and fully inflated tires beat my airstream to death, I'll scrap it and buy one that will go to Mars. We'll probably be doing that by then . However, I'm not too worried about that.

Ken

[Gene]

Jason is right that this will probably never be settled, but we keep trying.

As I understand it, ST tires were designed to have a stiffer sidewall than radials because of unique stresses on trailer tires, especially when backing and more especially while backing at severe angles. ST tires will skip sideways when backing at those angles, but LT's are less likely to. Their sidewalls flex and when they break free, they really jump. Put enough pressure on a sidewall and the tire will come off the wheel. This is very difficult to do, but whether the stress will damage the tire—invisible to you—is unknown to me. The flex in the sidewall means better traction at highway speeds unless you go much too fast—then they break free and you skid. Most people never experience that except maybe on snow and ice, or if they want to see how fast they can go.

Unfortunately, ST tires have many other problems, well documented on this Forum and on others. Radials have improved greatly over the years and some are built with steel cords in the sidewalls as well as in the tread. The Michelin Rib tire is one of those. Backing at extreme angles is to be avoided with any tire. As I have learned backing, I find I rarely ever have to back at extreme angles. That comes with experience.

One way to have a stiff sidewall is to inflate tires to the max allowed for a specific tire and wheel. I run Load Range E tires on the trailer at 72 lbs., not 80. Rednax recommends 80 lbs. He has more experience with trucks and trailers than most of us and he may be right.

Gene

[purman]

Originally Posted by w7ts

You will not get an answer from them because they don't recommend truck tires on trailers. Until they do you will have to use whatever information you can find if you put LT tires on your trailer. You and only you have to live with what you choose. There are other who choose to do differently. They have to live with their decision also. You can't expect an company to spend money on research on how to use their product in a way they don't recommend.

Personally I am going to inflate mine to the max, because I'm pretty close to that anyway, and I believe that's the safest.

When my stiff suspension and fully inflated tires beat my airstream to death, I'll scrap it and buy one that will go to Mars. We'll probably be doing that by then . However, I'm not too worried about that.

Ken

If I ran closer to the weight max I would run them at the max. If you are running max you won't beat it to death. I think I would beat mine if I ran them at 80. Or at least give it a hard ride.

From what I have been able to read and not from tire companies The ST tires have thicker nylon side wall cords in them. The side walls on my D tires where 2 ply nylon cords. The same as my E rated LT tires. But I don't know if this is true as I can't find that info on any tire web site.

[slowmover]

What is to misunderstand? Trailer tires are a subset of RV tires, and as such are subject to forces not seen by all RV tires.

One can use the term interply shear as reference to this force in ones reading elsewhere. The type of tire used on a trailer does not change this, not does the need for greatest resistance to this force (which is maximum sidewall stated air pressure).

Read through Roger Marble's blog on RV tires (tireman9, on the forums to which he posts) for more info.

.