Truck tire pressure

[Marveltone]

You run you pickup tires at 80 PSI, and the centers don't burn out? Not too be smart, but that defies physics unless the truck is only driven on grass.. There can't be more than 1.5 inches of tread contact unless the truck weighs 10 tons...Even then.....

My truck calls for 30PSI by spec, and 6lbs of overinflation caused premature wear on the centers of my rear tires in 1,00 miles..Max sidewall is 44lbs. I would be replacing the tires at 8,000 miles if I did that.

Not arguing...Just sayin'

You seem to be missing the fact that different vehicles will have different load ratings, and so will the tires. Heavier load ratings will mean higher air pressures. For example: A 1/2 ton truck tire may be rated for 35-50 psi, while a 3/4 ton will be much higher, like 60-80 or more.

Just sayin'.

Joe

 

[oldyellr]

Ok, i happened to be looking for some vintage tires for a buddies old hot rod Cadillac project and while at the Coker tire site, emailed them asking what they recommended as far as following air pressure settings.. meaning, do i inflate to the max PSI on the sidewall, or something else... THEY recommended the following...

Craig,
For a smoother ride and a declined chance of tire issues we suggest running
the suggested air pressure usually marked on the side of your tire from the
manufacturer.

Thank You,
Richard Stephens
Web Support

End of story for me... but i get it won't be the last entry on this thread.

Tires for old cars must be a special case. Just as an example, I looked up tires for a 1948 Cadillac on the Coker site and got this:

U.S. Royal 3 1/2 Inch Whitewall 820-15

Note that it says "Load capacity: 1920lbs @ 32 PSI", so 32 psi is probably the max pressure marhed on the sidewall and it likely IS what you'd want to run those tires at. For comparison, the 245/50-16 tires on my 1985 Camaro show 730 kg (1609 lb) at 44 psi on the sidewall, but nobody would run them at 44 psi (the door sticker says 30 psi).

Of course most modern car and "truck" (suv, mommyvan, luxury pickup) tires are way oversized due to styling considerations, so running them at maximum pressure for their size and load rating would be overkill and yield a very harsh ride. Perhaps old cars and actual working trucks (and trailers) don't have these oversize tires just for looks and therefore their maximum pressure is actually closer to the working pressure.

 

[milkman636]

VERY wise question!

Unless the tires on the vehicle are the ones it was BORN WITH, the pillar chart is WORTHLESS (I would argue it is worthless in any event, re: Explorer)...............................................BTW, this is a "trick" question.... What is the PRIMARY deciding factor in the pressures listed on the pillar charts supplied by the OEM?
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NVH - Noise, Vibration and Harshness. aka, Ride "quality". I for one, do not consider it to be good ride quality when you flip onto the roof because the tire failed from under inflation by the TIRE manufacturer's recomendations.

This is exactly right. The "ride" engineers and purchasing people have too much influence on manufacturer tire selection and placard pressures.

Personally I air the D-ranges on my truck up to the 65 psi sidewall pressure for towing and hauling, but I'll air them back down to 55 front and 50 rear for ride quality if I am going to be driving around light for a while. Leaving them aired up while running light is like skipping a stone down the road. Changing air pressures only takes a couple of minutes to do, and it tunes my ride for what I'm doing.

 

[dodge man]

Ya can't go by Coker tire, they make a bunch of stuff for old cars, a lot of which is bias ply stuff.

 

[oldyellr]

Ya can't go by Coker tire, they make a bunch of stuff for old cars, a lot of which is bias ply stuff.

I grew up with those darn bias ply tires in a town with streetcar tracks. Talk about a wild ride! Radials were 1000% more stable on the tracks, but they were almost unknown in North America, except for BFG and imported Michelins and Pirellis, sought after by the sports car people. Back then the sidewall rating, if there was one, would be about what you'd use because the load rating of tires was more closely matched to the application, unlike today's wide tires. So I can see why TheTrailerGuy was recommended the sidewall pressure by Coker for old style bias ply tires.

 

[TheTrailerGuy]

I grew up with those darn bias ply tires in a town with streetcar tracks. Talk about a wild ride! Radials were 1000% more stable on the tracks, but they were almost unknown in North America, except for BFG and imported Michelins and Pirellis, sought after by the sports car people. Back then the sidewall rating, if there was one, would be about what you'd use because the load rating of tires was more closely matched to the application, unlike today's wide tires. So I can see why TheTrailerGuy was recommended the sidewall pressure by Coker for old style bias ply tires.

AH! DAng it!! i promised myself i wouldn't get drawn back into this debate...

As my attorney always says, "I hate to confuse this conversation with something pesky like an actual fact... but.. "

1. Coker tire Coker Tire - Your Source for Antique Tires and Wheels as you can see by simply clicking a button isn't some backwater craphole that knocks off just bias tires. It is the worlds LARGEST specialty tire company, doing well over $500 MILLION In sales annually, which leads me to believe that they do not hand out tire inflation advise offhandedly.

2. This group has been having the same discussion and are having about as much luck... Tire pressures - Sidewall vs. door pillar - Allpar Forums for Chrysler, Dodge, Jeep, Plymouth, and more

3. B.F. Goodrich says.... BFGoodrich Frequently Asked Questions | BFGoodrich Tires

4. Firestone has this really cool demo showing what different inflation pressures look like on a tire... http://www.tiresafety.com/inflation_11.swf

Other than that.... i guess you engineers will all figure it out. Me.. i like good, stiff tires that handle sweet. i keep mine within a few pounds of max sidewall pressure all the time.

God Bless.. now let's start a new thread. show me your shredded trailer tires! I know you guys have popped a few over the years. did you get any photos?

 

[JIGBUILDER]

I use different tire pressures in my wifes 1500 crew cab chevy 4x4 with P265/70-17 tires. I'm a old guy and have always used the chalk line for determining best tire pressure for the tire/wheel and the trucks ladin and unladin weight. Wheel width has much to do with how flat a tires contact patch is with a specific tire pressure.

When empty I've found that the full 44 psi works best in the front tires and 38 psi in the rears on the rough county roads around here. Her trucks door tire pressure placard call for 35 psi in all four. With 35 psi they were wearing the tires edges and the tire had to much compression/rebound in the sidewalls (basketball bounce). The Z71 suspension/stiff shocks probably has some input there also.

When pulling any of my trailers I use max 44 psi pressures in the rears.

Don't forget a P tires capacity on a truck is required by fed law to be derated 10 percent.

 

[whateg0]

You shouldn't forget that a tire that is inflated to a higher pressure has a smaller footprint and that means less braking ability. I also find it a bit funny that people say you should never trust the manufacturer of the vehicle to know what they are talking about because of one bad example. I would hazard a guess that because of the liability involved, most of the time, the vehicle manufacturer is going to recommend a pressure that is well above a range that would endanger the tire and thus the car, and then lead to a lawsuit - again.

Just my 2.1¢.
Dave

 

[SPYDERLK]

3. B.F. Goodrich says.... BFGoodrich Frequently Asked Questions | BFGoodrich Tires

4. Firestone has this really cool demo showing what different inflation pressures look like on a tire... http://www.tiresafety.com/inflation_11.swf

3 - Good answer to the tire inflation question.
4 - Note that a low profile tire is used for the demo. These are very sensitive to low tire pressure due smaller sidewall [heating] and much more likely bump pinch causing rim and tire damage.
larry

 

[SPYDERLK]

You shouldn't forget that a tire that is inflated to a higher pressure has a smaller footprint and that means less braking ability. Just my 2.1｢.
Dave

Gravel ... and washboard surfaces.
larry

 

[milkman636]

...............I also find it a bit funny that people say you should never trust the manufacturer of the vehicle to know what they are talking about because of one bad example. I would hazard a guess that because of the liability involved, most of the time, the vehicle manufacturer is going to recommend a pressure that is well above a range that would endanger the tire and thus the car, and then lead to a lawsuit - again.

Just my 2.1｢.
Dave

Its not about trusting them. Its just that the manufacturers have to pick a single compromise number for tire inflation that suits every operating condition that your truck will experience within its design parameters. They have hours of meeting where groups of engineers discuss why their number is the best. Then they settle on a compromsied specific number. That's one of the reasons new vehicles cost so much. We simple minded:confused2: owners can't be trusted to make our own judgements about loading and tire pressures.

 

[Egon]

You shouldn't forget that a tire that is inflated to a higher pressure has a smaller footprint and that means less braking ability./QUOTE]

According to some long ago physics the contact area does not matter.

 

[JasG]

You shouldn't forget that a tire that is inflated to a higher pressure has a smaller footprint and that means less braking ability./QUOTE]

According to some long ago physics the contact area does not matter.

Going by this in dry PSI have very little impact, but wet higher PSI can be better. Basically in dry condition you are correct it doesn't seem to matter.


The braking distance is at the bottom with comments about the findings.
TIRE PRESSURE SURVEY AND TEST RESULTS

 

[oldyellr]

You shouldn't forget that a tire that is inflated to a higher pressure has a smaller footprint and that means less braking ability.

According to some long ago physics the contact area does not matter.

I remember that too and believed it at the time. But that was before tire technology was developed to where acceleration, cornering and braking forces started to go above 1 G.

 

[Reg]

Going by this in dry PSI have very little impact, but wet higher PSI can be better. Basically in dry condition you are correct it doesn't seem to matter.


The braking distance is at the bottom with commenst about the findings.
TIRE PRESSURE SURVEY AND TEST RESULTS

Where it MATTERS is when there is standing water on the road.
Lower pressure translates to larger area, leads to easier hydroplaning - at which point braking and steering are GONE AWAY.
This is why WIDE tires are such a bad choice, they LIFT too easily on water.

 

[Egon]

Thanks for the information JasG.:thumbsup:

 

[JasG]

Thanks for the information JasG.:thumbsup:

Your welcome.

 

[zzvyb6]

Sorry to have to correct some misinformation here, but the EPA now pretty much sets the required pressure in all car and truck tires because of rolling resistance (fuel economy) demands. Requirements are set by a coast-down test which is then used to recreate the roadway conditions on a chassis dynomometer.

Stopping distance effects are not an issue because the tire construction recipe is then established by the tire manufacturer in order to meet dry, wet and sometimes snow traction requirements of the tire for braking and traction in order to meet MVSS105 stopping distance requirements. These are requirements set by Federal Law, not some arbitrary committee at a vehicle design or marketting meeting. Additional tire properties are set by design if ABS is used to meet stopping distance.

That's why I only buy OEM tire manufacturer brands. Its no secret in the industry that off brand tires have dismal performance for rolling resistance, traction, durability and longevity. If low cost is your need, low performance comes along with it. Amongst these brands, only the models with certain key symbols on the sidewall actually are equal to the OEM tires. GM's TPC, BWM star and Mercedes codes are well known.

 

[oldyellr]

Sorry to have to correct some misinformation here, but the EPA now pretty much sets the required pressure in all car and truck tires because of rolling resistance (fuel economy) demands.

That likely explains why the door pillar tire pressure numbers on today's cars are higher than they used to be 40 years ago and why a lot of "old timers" never trust those numbers and use the maximum sidewall number instead.

 

[xtn]

Sorry to have to correct some misinformation here, but the EPA now pretty much sets the required pressure in all car and truck tires because of rolling resistance (fuel economy) demands. Requirements are set by a coast-down test which is then used to recreate the roadway conditions on a chassis dynomometer.

Stopping distance effects are not an issue because the tire construction recipe is then established by the tire manufacturer in order to meet dry, wet and sometimes snow traction requirements of the tire for braking and traction in order to meet MVSS105 stopping distance requirements. These are requirements set by Federal Law, not some arbitrary committee at a vehicle design or marketting meeting. Additional tire properties are set by design if ABS is used to meet stopping distance.

That's why I only buy OEM tire manufacturer brands. Its no secret in the industry that off brand tires have dismal performance for rolling resistance, traction, durability and longevity. If low cost is your need, low performance comes along with it. Amongst these brands, only the models with certain key symbols on the sidewall actually are equal to the OEM tires. GM's TPC, BWM star and Mercedes codes are well known.

It is my experience that OEM tires are not the absolute best available at all. They certainly aren't the worst choice and you could do a lot worse, but if you research you can do a lot better too.

But of course "better" totally depends on the qualities that you value as an owner. Better dry grip? Better longevity? Better NVH? Better foul weather performance?

On my car I choose to give a high value to dry grip, a secondary value to turn-in feel, a distant third value to longevity, and almost no value at all to any other quality. Therefor I choose an 'R-comp' DOT legal tire with a 60 treadwear rating that I like the feel of. If your criteria are different than mine you would hate this tire. I get about 4,000 miles out of a set, they have a lot of rolling resistance, they hydroplane at the drop of a hat, are not much good below 50degF or when driven in the rain and when used hard they sling little drops of rubber up onto the body of my car. By by my personal standards for that particular car and what I expect out of driving it, they are "better" than any other choice.

So depending on one's usage and criteria, OEM is not automatically the best. My aftermarket tires stick better, are faster around the track and cost less than OEM.

xtn