Proper PSI For Trailer Tires?

[Tumbleweed13]

I'm curious as to what you consider the correct psi, to put into your trailer tires? I have a toy hauler, 28' twin axle. Fully loaded i'm 15 - 16K lbs. The max rating on the tires, is stated at 80psi. I've always pumped them up, to 75psi. Giving me a bit of room for pressure increase, due to heat.

What do you guys think?

I have a buddy, that has a very similar set up, and he only runs 50psi. His tires have the same max psi as mine. Is this ok too?

That are your thoughts on this?

Thanks, Joe

[Ohio_Engineer]

The OP question was about trailer application. Most have the correct answer of using the pressure molded on the tire sidewall that is associated with the max load.

Because of the unique suspension i.e. when turning any curve or corner the tires do not rotate around a center-line that points to the center of the turn radius. This results in what is known as a "slip angle". This means that the "Interply Shear" force (the force that is trying to tear the belts of the body) I provided a link to the Google search results for "Interply Shear tires" for those interested in the technical details.

Motorhomes and other motorized vehicles do not have the same level of Interply Shear so they can inflate based on measured load, but I strongly suggest a cushion of +10% on the inflation needed to support the load so you don't have to chase your tail every day as ambient temperature changes.

[BenK]

Tire PSI is not just to hold/carry weight...there are many duties that tires have
to do...carry weight is only ONE of them

Proper PSI is more to do with keeping the tire's shape while it is doing all of
those duties...directional, stopping, acceleration, and shock absorption

Directional is straight line, slalom, curves, cornering, etc. Within them is the
slip angle, roll over resistance, transition times, etc

More weight will have the tire's shape changed and even more so during maneuvers

Of course, it too low or too much, the tire tread will wear unevenly

[Cummins12V98]

If you have the OE load range tires on your RV running the MAX load rating is "usually" the correct answer.

All of the DRV Mobile and Elite Suites for example run the GY "H" tires. Per the weight/inflation chart I need to run MAX @ 125psi with my two axles weighing in at 17,500#.

A tripple axle or a lighter unit than mine can and should run 5psi over their actual tire weight's recommendation on the weight/inflation chart.

Benefits per GY is having better tire wear, better traction and a better ride for the RV.

Same goes if you are upping the load rating as I did on my 36' MS. I went from GY "G" to GY "H" and ran the tires at 105-110psi based on my tire weights. After thousands of miles the tires looked great.

[ktmrfs]

Tumbleweed13 wrote:
Thanks for all the responses, and info. A few mentioned ride comfort in there responses. I should have been clearer. My main concern is for tire wear/ degradation. I'm more worried of blow outs and failures than a smooth ride. Thanks again.

My experience, along with a neighbor that has put over 100K miles on his cargo trailer is that running at max sidewall pressure for tires of the same size as specified originally you'll see normal tire tread wear even if you go up on load range.

BTW neither of us have had any blowouts either. But then we both have TPMS as well, and it did catch a nail hole I had that was causing a tire to loose enough air.

In my case I've run 25K miles on a set of ST tires LRE at 80psi replacing LRD 65psi tires and the tires were worn evenly. Same with the neighbor who went from LRD to LRE.

Now I imagine that if you go with larger tires and much high load rating eventually you'll end up wearing the center of the tread first.

[Tumbleweed13]

Thanks for all the responses, and info. A few mentioned ride comfort in there responses. I should have been clearer. My main concern is for tire wear/ degradation. I'm more worried of blow outs and failures than a smooth ride. Thanks again.

[LIKE2BUILD]

Tumbleweed13 wrote:
I'm curious as to what you consider the correct psi, to put into your trailer tires? I have a toy hauler, 28' twin axle. Fully loaded i'm 15 - 16K lbs. The max rating on the tires, is stated at 80psi. I've always pumped them up, to 75psi. Giving me a bit of room for pressure increase, due to heat.

I have a buddy, that has a very similar set up, and he only runs 50psi. His tires have the same max psi as mine. Is this ok too?

Trailer tires are rated at max PSI when the tire is cold and are engineered to withstand the pressure increase due to heat build-up. Those pressure ratings are intended to maintain proper tire shape (tread and sidewall) during operation to withstand the rated load.

I always run trailer tires at MAX RATED PSI regardless of the load on the trailer. This is to ensure the sidewall is supported and I'm not causing excess wear on the tires. Your buddy running Load E tires at 50PSI is flirting with disaster. Run the tires at max and they will stay cool and perform as designed.

KJ

[deltabravo]

Tumbleweed13 wrote:
I'm curious as to what you consider the correct psi, to put into your trailer tires? I have a toy hauler, 28' twin axle. Fully loaded i'm 15 - 16K lbs. The max rating on the tires, is stated at 80psi. I've always pumped them up, to 75psi. Giving me a bit of room for pressure increase, due to heat.

What do you guys think?

Run them at 80 PSI. You don't need to run lower PSI to allow for heat expansion. The tires are always marked with a pressure, followed by the letters "PSI COLD"

[Wild_Card]

RedRocket204 wrote:

Wild Card wrote:
For example my dually rears are rated 65psig...and thats what is on the door sticker. If i am unloaded its ridiculous tonrun max psi. Sometimes too much air is a bad thing

And what you are addressing is for a motor vehicle... not what the OP asked about as the OP's question was concerning trailer tires.

I used this as an example...what i am addressing is that every tire mfg...be it LT,ST, or P rating Automobile, truck, trailer, ATV and Streetbike has a load to psi chart.Every tire.

I have G rated tires on my trailer that gross's 11k...why the hell would i run max psi in them? There is not enough load to flatten the tread...so it will wear the middle tread faster.

[Wild_Card]

tinner12002 wrote:

Wild Card wrote:
For example my dually rears are rated 65psig...and thats what is on the door sticker. If i am unloaded its ridiculous tonrun max psi. Sometimes too much air is a bad thing

That's funny because my dually tires are rated at 80psi just as the fronts. Door sticker says to run 65psi for max load but other than ride quality if I had 4-5K on my pin I do think I would bump it up above 65psi. Just my opinion. As for the OPs question, I run anywhere between 75-80psi in my trailer tires. Tires are rated at 80psi at max load so that's what I start out on trips with, if it drops to 75psi overnite I don't worry as the psi comes up when traveling and as outside temps come up.

I think i pretty much stated in my post that it was the door sticker that stated 65psig for max load. Of course they are rated for 8o...they can be rotated to the front which is max load of 80 on the door sticker

[JIMNLIN]

Lets go one step farther from Goodyear germane to the subject which is tires on trailers; trailer tire pressures

Special Considerations
**Unless trying to resolve poor ride quality problems with an RV trailer, it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up.**

Goodyear mentions a poor ride quality which would be someone who has over tired their trailer such as one poster on another website who mounted a 17.5" 16 ply rated load H Sailun S637 at 6000 lbs per tire on light loaded 7k axles.

[drsteve]

I always run my trailer tires at the max inflation listed on the sidewall, and I have never had a problem of any kind.

[mike-s]

ktmrfs wrote:
In fact many of the trailer tire mfg. state the tires are designed to be run at max inflation pressure regardless of load

Citation? Because, Goodyear says this:

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.

...and backs it up by publishing load/inflation tables which show pressures less than the max for a load range.

[ktmrfs]

mowermech wrote:
You can always try the "chalk test" to find the CORRECT tire inflation.
Make a chalk mark or two (or more) across the tread of the tire. Drive a few yards on a hard surface, then look at the chalk mark(s).
If the chalk mark(s) are worn off evenly across the tread, the inflation is just right for the present load.
If the chalk mark(s) are worn only on the sides of the tread, the tires are under-inflated for the load. Add air.
If the chalk mark(s) are worn only in the center of the tread, the tires are over-inflated. Remove air.
For best traction in braking and turns, the contact patch between the tire and road must be as large as possible. Over or under inflation reduces the size of that contact patch, and wears the tread unevenly.

I'll disagree with contact patch related to pressure. the info on using chalk to see if your near correct on inflation is a common tool, well characterized.

contact patch area is very linearly related to pressure once you've got a reasonable pressure in the tire. contact patch area in square inches will be very close to the weight the tire is supporting divided by the tire pressure in psi. Contact patch SHAPE is highly dependent on the aspect ratio of the tire.

At very low pressure it is not linear because your also then dealing with the sidewall stiffness in the equation.

High inflation reduces the area of the contact patch while low inflation increase the area of the contact patch for a given load. The shape will change as well.

the shape and area change both change traction characteristics along with the effects of sidewall deformation with lateral load with varying pressure.

[ktmrfs]

Turtle n Peeps wrote:

mike-s wrote:
Tire and loading sticker on the left side, in front near the bottom.

PSI is cold pressure, if it calls for 80 PSI, put 80 PSI in when cold. 75 PSI would be underinflated. The given pressures already take into account any pressure increase from heat.

This ^^^^^. I personally run max or even max +10. In 40 years I had one blow out.

Ditto, with the comment this is what I do for my TRAILER. TV and cars trucks etc. run what the mfg recomends.

In fact many of the trailer tire mfg. state the tires are designed to be run at max inflation pressure regardless of load.

And I do that even though the load capacity at max pressure is much higher than the actual load. and the tires still wear very evenly.