Tire Pressure - MAX vs DATAPLATE

kellertx5er- wrote
"Sorry, but this is not much of an example. You failed to give any facts which support the decision to inflate to max PSI. It only seems that load range C tires were not suitable for the job. "

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The examples I gave were to illustrate that the dataplates are for original equipment tires. Sometimes the tires get upgraded so the dataplate info may be incorrect.

I also included the suggestion to use the manufacturer's website to determine the correct pressure for the load.

To my conclusion the sheer forces are not the reason why the tires damage, if the stucture is undamaged that is.
The damage of the structure of the rubber of the tire is courced by to high temperature at critical rings of the tire , the tire produces more heat that can be cooled down , by to much deflection ,or better bending of the rubber,times number of cycles the tire makes a second.

Especially ST tires are calculated in their maximum load for more deflection allowed at the lower speed of 65m/h.
Asuming this calculation is right done, then still its to the edges.
If then some overloading on a tire, or lower pressure cold( misreading of scale or inacurate device) and the deflection gets to much so to much heat production and temperature of the critical rings gets to high and rubber hardens , and at next bendings , so deflections cracks .

Then when sheer forces , even at the lower speeds they happen, these cracks tear the tire apart.

Best is to give the ST tire a pressure of the given pressure of tire, to build in some reserve so it wont get to hot. Even the 10 psi higher or for truck tire 20 psi for 75 m/h can be needed , even if you keep yourselfes below 65 psi.

for your normal car the 51 psi is the maximum cold pressure and not the pressure needed for the maximum load , this is for P tires always 35 psi ( american TRA system), and there they are calculated for 99m/h the deflection. Because you probably never drive this speed, so for normal cars the pressure can be lower then max given.

"JIMNLIN"....gave a GREAT answer as to why trailer tires should be run at max pressure!

the bear II wrote:
Here's an example:

The company I work for has a fleet of vehicles we can use when going out in the field. One is a chevy 2500 long bed extended cab. Originally from the factory it came with load range c tires with a max PSI of 35. That's what the data plate shows on the door. When the tires were torn up on a rocky road, they were replaced with Load Range D tires. The sidewall shows max is 80 PSI

Similar with a Jeep Cherokee. The tires were replaced with a higher load range tire.

That being said many tire manufacturers on their websites provide charts which indicate the acceptable PSI based on the actual load.

I always keep my tires inflated to the Max PSI indicated on the sidewall. I don't have the time to adjust the pressure depending on load I'm carrying.

Sorry, but this is not much of an example. You failed to give any facts which support the decision to inflate to max PSI. It only seems that load range C tires were not suitable for the job.

Why? 50 years of driving many types of vehicles towing many different trailers on literally 100's of tires.

Do what you like and I'll do what has proven to work.

The OEM tire inflation plate is only valid for the OEM tires. Once you have changed them then other variables come into play

Are those 120 MAX psi tires the OEM tires that data plate recommends 80 psi for ??????

Have you weighed truck/trailer?

dcmac214 wrote:
A LOT of replies to tire threads recommend running the trailer (and I assume also car/truck/motorhome) at sidewall max psi instead of the dataplate psi. Why?

Bad assumption- I do not believe *anybody* has recommended ignoring the data plate on a motorized vehicle- only trailers.

All of the issues with over inflation are not present in a trailer- rather we want the tire to run cooler, and we want the sidewall to be stiff, to reduce sway. Few people will actually wear out a trailer tire.

120 psi trailer tires are certainly not the norm- I have never seen one on anything other than a semi trailer, or smaller than a 22.5. What are they, H load rated?

I think that comparing cars/trucks with trailer is comparing apples and oranges to a certain degree.

I think the trailer tires should be closer to sidewall max pressures because of the stresses that the trailer puts on its tires. Seems to me a fully inflated tire will withstand cornering and scrubbing issues better than a tire that is softer and only partly inflated. But that's strictly IMO.

FWIW however, Goodyear did have a notice on their website that recommended inflating RV tires to max sidewall pressures.

A LOT of replies to tire threads recommend running the trailer (and I assume also car/truck/motorhome) at sidewall max psi instead of the dataplate psi. Why?

Our RV trailer axles are close spaced and in the center of the vehicle vs say a truck with the axles at the corners with the front set steering into the corner and the rear set following. Now watch the trailer tires as they slide sideways (side scrub) around the corner. This action is trying to tear the tire apart....so tire experts and experienced trailer owners have found max sidewall pressure gives their tire the best shot at staying together.

My trailer tires have a max psi of 120. The trailer dataplate tells me the correct psi is 80. So I follow the manufacturer recommendation 80psi. I figure they know better than anone else what's 'right' for my trailer.

If you believe that then no use asking us anything :). Anyhow.....
Somethings not right. I've never heard of a trailer mfg recommending derating a tire on their trailer by 25 percent. Doesn't make sense or
It sounds like some one has upgraded a ST235/80-16 E tire at 80 psi to a much higher rated tire. If thats the case the trailers tire data plate will not reflect the right pressure.

This from a good source when some one has over tired the trailer;
rvsafety.com

Tire Load and Inflation Ratings

Note: Towable – Travel Trailer/ 5th Wheel owners Due to the severe use conditions experienced by tires when axles are very close together – tire industry experts recommend maximum (sidewall) inflation pressure for towable tires unless this causes a sever over-inflation situation (20psi+), often referred to as the ‘basketball effect’. If this is your situation allow a 10 – 15psi safety margin above the minimum required inflation pressure.