tire pressure myth?

[GreyGoose006]

truthfully, i cant even read what is on my doorpanel.
secondly, on every car that i have ever looked at at the dealerships, the recomended pressure on the doorpanel is within 2-3 psi of what the tires say.
have you ever noticed that you never see sidewalls that say inflate to 47.5 psi?
they are usually rounded to whole numbers, and about %75 on the time, rounded to either a 5 or a 0.
owners manuals and door panels too...
you never see an owners manual that says inflate the rear tires to 27 psi and the fronts to 31 psi. this would make sense on say a ford ranger, where you know it wont carry much weight, and if it did, it is not much.
in trucks, the majority of the weight is in the cab, on the front axle, yet the tire pressures are usually the same front and rear.
even on high end sports cars, tire pressures are kept at 5 or 0 intervals for the most part, and are the same front and rear.

HMMMM...

[534BC]

A side road that may be related is the number of times pressure is checked. My friend told me He checks his tire pressure when He fuels up. I said surprisingly "every time?" He said "YEP" I slyly said " Well, do you ever have to add air?" He said Yes He does a lot of times.

I told him I add air to all my tires about once per year when the weather is on a downward temp. I also told him if tires do not leak air then they never need aired up. He kinda looked perplexed.If I had to add air then I would assume it has a leak.

[GreyGoose006]

tires on trucks that see ranges from 2-50 tons are a slightly different issue as this is a much larger range than the average ford taurus' tires will likely ever see.

[GreyGoose006]

thats true tho, if tires dont leak than they dont need to be filled.
(seems obvious to you and me but you'd be surprised how difficult a concept this is to some people)

[Steel]

Dude.
You're nuts.
I see door stickers say 28-29-31-32-33 psi all the time.
the sidewalls on my car are 35psi max on the rear, and 44 on the front. That shoots down your whole "rounded to the nearest 5" idea.

2-50 tons? I don't know of any tire made for that wide of a range. E load tires are usually good for ~3500pounds at 90PSI. That's 1.75 tons. Per tire. Even the trailer truck tires arent rated for too much more than that. Want to put more weight on? Easy - add more tires. That's why trailers usually have 16 tires to distribute their load on (2 per side per axle, and 4 axles).

[534BC]

I think the door panels are maximums as well (for the max load)

I learned a long time ago that each ply was to carry a max of 7 pounds. Don't know if that applies to todays tires.

[GreyGoose006]

i've never seen it. thats all i'm going off.
really? becuse every car i've ever looked at the owners manual to rounds to a convenient number.
who knows?

[534BC]

Originally Posted by Steel

Dude.
You're nuts.
I see door stickers say 28-29-31-32-33 psi all the time.
the sidewalls on my car are 35psi max on the rear, and 44 on the front. That shoots down your whole "rounded to the nearest 5" idea.

If I had those tires and wanted to rotate them , I'd have to put my 3 fat friends all in the back seat.

[GreyGoose006]

Originally Posted by 534bc

If I had those tires and wanted to rotate them , I'd have to put my 3 fat friends all in the back seat.

still laughing...

[534BC]

Very serious matters, but I like to keep it lighthearted anyways and laugh. I hope my backhoe story made someone smile.

[GreyGoose006]

hehe, yeah.
so uh, why quit trying to slow the earths rotation?
if all of us lined up on the equator and all at once, everybody took off at the same time going west, i bet we could have an impact.
think about the thrust of billions of cars accelerating at once.
hell, we could probly reverse the rotation if we coordinated it right!

[534BC]

If we all had the correct tire pressure it would be a lot more effective.

[KiwiBacon]

Originally Posted by GreyGoose006

every time i get off the highway at a rest stop or something i check my tires by holding my hand on them and visually glancing to see that they are at the correct pressure.
usually, unless the wether is exceedingly hot, the tires are no warmer than what i'd say is 85-90* in the summer, and 80-85 in the winter.

You've missed the point.
You're not supposed to be checking for temperature, you're checking for temp variation across the treads.

Hotter in the middle = pressure too high.
Hotter on the edges = pressure too low.

Truck tyres are completely different construction to car tyres. Their sidewalls are so thick that if they are run at less than 90psi the flexing of the sidewalls causes them to overheat and disintegrate.

Further, grip of a truck tyre isn't comparable to a car tyre. Their primary goal is load carrying capacity, secondly longevity, thirdly rolling resistance.

[Knap]

Turn that around and have your 3 friends with luggage get in and then proceed to drive at high speed down the "freeway" - how many ordinary motorists adjust pressures to suit.

Experiment at home, pump up tyre measure psi, then fit and measure psi.

[gdeland]

I work for a major tire manufacturer, there is ALOT of misinformation on this thread. The correct tire pressure is determined by following the VEHICLE manufacturer recommendations, NOT WHAT IS ON THE SIDEWALL OF THE TIRE!. The sidewall lists the MAX air pressure, i.e. what the tire will hold for psi for the MAX Load. The tire does not know what type of vehicle it is going on. ALWAYS look at the door jamb for the vehicle manufacturer's recommendations. Usually for passenger vehicles this is in the 30-35 psi range.