Tire pressure when towing

[TiredTrucker]

Works in general practice most times. But also the fact that the OEM isn't forthcoming with all information is also in play. And tires are NOT spec'd by the OEM, but by the tire manufacturers. Vehicle OEM's do not develop and R&D tires and make them. They put out minimum standards, obtain buy contracts with suppliers that give them that minimum standard at the lowest cost. Then, they recommend inflation pressures based on GVWR.

On commercial truck tires, the vehicle OEM's stay out of the tire pressure game, as they should, and let the tire OEM's provide the proper inflation based on the load on the tires for maximum performance, maximum life, and maximum safety concerns based on the tire design characteristics. That inflation guideline changes as weight loading on the tires change. An over inflated tire for the actual loading on them can be as detrimental and an under inflated tire. Maybe not in terms of the risk of a tire blowing, as would be the case with an under inflated tire under heavy load in hot weather, but in terms of negative effects on traction (and subsequent tire wear) and braking ability, putting both the user and others at greater risk. A tire is developed to have a certain amount of footprint on the road surface. A tire that is over inflated for the load has a decreased foot print. And depending on the actual compound used for the tread, improper inflation for the load can cause loss of performance characteristics. And an overinflated tire for the load, since it cannot flex properly, will put additional shock loading on the suspension components. Again, a negative.

While the vehicle OEM recommends an inflation, we all know that all tires are not made the same way, with the same compounds, and with the same tread and sidewall designs, even within the same class. And vehicle OEM recommendations do not factor that in also.

 

[Ramblejam]

Originally Posted By: TiredTrucker
(and subsequent tire wear)


True. Whole bunch of pickups running around unloaded with 80 PSI in their rear tires that just wear out the center tread.

 

[CapriRacer]

Originally Posted By: TiredTrucker
Works in general practice most times. But also the fact that the OEM isn't forthcoming with all information is also in play. And tires are NOT spec'd by the OEM, but by the tire manufacturers. .......


I'm going to truncate the post so as to not take up space, but I am going to comment on a lot of what was in that post.

TiredTrucker, I hope you understand that I am not picking on you, but your post has a lot of common misconceptions about OEM tires - ones that others also have and some of that needs to be corrected,

First, here is a page I wrote up on OE tires: Barry's Tire Tech: OE Tires

Short version:

In passenger cars and light trucks, OE tires must meet the specs published by the OEM (Ford, General Motors, Toyota, etc.) Those specs result in a pretty tight box. While the tire manufacturer is the one with the R&D, the OEM also does a lot of tire R&D work as the OEM's do vehicle handling modeling and test the tires for *Force and Moment*, so they know a lot about how tires behave.

They also specify many tires in a given year and have developed a good amount of expertise as to what the treadoffs are and how far they can push them. The vehicle manufacturers also do a ton of ride and handling work.

The result is that without exception the tires that come on a new vehicle from the factory is unique to itself. It is unlike every other tire, even though the name on the side may be the same as another.

And it isn't always that the cheapest tires gets sourced. When I was involved in the process, Ford divided up the sourcing such that it was more or less that same percentage from year to year - with a couple of percent incentive to get the best supplier rating. This meant that a lot of time and effort was put into the selection process by the purchasing depart to get the best mix of cost and performance - and sometimes that meant a given given vehicle didn't always get the least expensive tire.

Oh, and the cost was set long before the tire was through the development process. In other words, the tire manufacturers set their prices BEFORE they actually knew what the costs would be. It was a bit of a c*r*a*p shoot.

In commercial trucks, this is done differently. Commercial truck buyers specify the tires they want - and if nothing particular is specified, the OEM will supply the standard tires they pre-select - which is a standard over the counter product, not specially designed.

Also, nowadays the designs of tires are such that many tire properties don't change much with loading and inflation pressure. Wear and handling are such such properties. The grip level may change, but the way the tire reacts - not so much.

I hope this clears up a few things.

 

[TiredTrucker]

Well, I have hauled a lot of production auto parts, including many truckloads of tires to the assembly plants. I have discussed tires with the suppliers. Not always is the same tire that goes to the plants the same tire that is at a tire dealer. In some cases, differing compounds are used that, while the tire does meet the OEM spec, it is not always the same tire level of performance and quality.

And I do know a little bit about loading and pressures. I average 445,000 miles out of a set of drive tires on my semis and around 225,000 on my steer tires. And still have 8-9/32 tread left with no uneven wear. Same methodology I use commercially, I use for my 2500 pickup. I deflate them to 55 for general purpose and light loading, and inflate them for heavy loading. I have noticed better wear since doing so many years ago. Wheels do not hop on rough roads nearly as much, thereby increasing tire tread life, when inflated more appropriately for the load. On my 2015, that causes the TPMS to have a fit, but that's ok. I easily ignore the TPMS just like I easily ignore the seatbelt warning when I am out on the property and not using the seat belt. Somewhere in the ballpark of over 5 million miles driving to my credit, and I have not caused a major accident, and tire related failures I can count on one hand over several decades.

Grip level does indeed change as you say, and that can have a detrimental effect on braking, control, and safety with a tire that is inflated more than needed for the load on them. This is another reason why I adjust pressures based on tire loading. I would like to be able to stop that 7000 lb pickup in the shortest distance possible instead of eating that van full of kids that just pulled out in front of me.

 

[meep]

...editorial comment from the peanut gallery. I commend you both for actually having differences in opinion and being totally comfortable in that without taking offense or turning it into a pi55ing match. Bravo. Respect. Says a lot...