Proper PSI For Trailer Tires?

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

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.

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.

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.

Snipped from Tireman9 rvtiresafety.com blog;

*When not driving in a straight line there are special side loads on multi-axle trailers because the tires are fighting each other because they are not "pointed" to the center of the radius of the turn. These loads cause interior structural tearing. Sometimes 24% higher loads than those seen in tires on non-trailer application. Initially tearing is at the microscopic level but with time and repeated cycles these forces grow which can lead to small cracks at the belt edges as seen here at the arrows.*
and
*You can lower these forces by either decreasing the load 24% on the tire (probably not something you want to do or may not be able to do) or you can increase the inflation to stiffen the structure and decrease the slip-angle. In this case you could increase the tire inflation from the minimum inflation needed for the static load to the inflation associated with the max tire load as molded on the tire sidewall.*

Also add the fact ...many trailers can weigh more on one side than the other. Using a pressures from a minimum pressure chart may cause the tire(s) on the heavy side to run over loaded.

A severally over tired trailer has its own problems with the best psi for the good of the tire.

mike-s wrote:

theoldwizard1 wrote:

TexasChaps wrote:
I run at max cold pressure as stated on the sidewall.. never had a problem.. ever..

Correct !

Maybe, if the original spec tires are installed, and the camper is loaded near its load capacity. If the max load calls for a LR B tire (35 PSI), but LR C (60 PSI) tires were installed, inflating to the max is probably not the thing to do. It will cause a harsher ride. A LR C tire at 40-50 PSI can provide a compromise between more load capability (margin/safety/longevity/reliability, which can be a separate argument) and an overly harsh ride.

Car and truck tires are frequently specified at less than their max load pressure, simply because the max load isn't needed.

And, some TTs may be similar - the tire/pressure label is what to go by, not what's marked on the tire sidewall.

quite right, but you will find that most OEM specified trailer tires are marginal at best.. hence all the talk of upgrading to larger sizes and or LT tires.. my TT for example has the same pressure on the sticker as the tire.. so on stock tires I would prefer a "harsher" ride than under inflated tires..

I've always ran my TT tires to the max psi on the tire which was the same as the TT's tire sticker. I now had E instead of D rated tires on. I run them lower than the max psi of 80 because they have a higher weight rating. You need to run the tire at whatever psi is applicable to it's load.

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.

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.

Exactly and also the advice per the tire shop.

You can weigh your trailer...all wheels...and get the answer needed to use a tire pressure chart to potentially soften the ride of the tires by using a reduced pressure....or you can get the maximum load rating of the tire by using the cold psi on the sidewall of the tire.

I'm a simple guy and want the max load rating on a trailer that is subjected to road forces, sway etc....but that's me. For my money, it does not make sense to accept a reduced load rating to soften the ride on a trailer. And yes...the sticker on the side of the trailer will tell you the pressure for the tires your rig came with...

Picking a number out of the sky or not checking the tires is not in your best interest...