What is the correct pressure for inflating tires? inside door label or side of tire?

[nonlinear]

What pressure do you guys inflate your tires to? my dad has some auto repair shops, and as a kid or when I used to work for him in high school, he taught me to inflate tires to the maximum pressure given on the side of the tire. However, i've read in many places (e.g. http://www.fueleconomy.gov/feg/maintain.shtml) that tires should be inflated to the pressure suggested by the vehicle manufacturer, which is given on the label on the side of the driver's door.

just curious, since i had my car in for an oil change today, and the guy let out the air from 44 psi to 32 psi (although i'm not sure if my door says 32, or if the guy didn't read the tire and just assumed it was 32 psi).

what do you guys do?

[revelations]

Chassis sticker - tuned by OEM to make car handle as intended.


If I changed tires and/or rims that signifigantly deviated from OEM, I would run something other than max sidewall PSI or chassis sticker.

[ercchry]

i thought you were an educated man? tell me... WHY THE HELL you would inflated to the MAXIMUM pressure when the tires are cold!?????!!!!

[Twin_Cam_Turbo]

I never ever inflate to maximum pressure unless im seating the beads. OEM reccomended pressure always unless its significantly different from stock.

[Sugarphreak]

.....

[rizfarmer]

I just had my car in to repair a flat and the shop inflated all of my tires to 40psi on a 2 door integra in the cold of winter. That's about 90% of max pressure and way up from the manufacturers recommendation. WTF?

btw I dropped it back to about 32 psi, which is still a little above the Acura recommendation

[nonlinear]

so I just looked at the sticker on my car door, and it says 30 psi for all the tires. the sidewalls say 44 psi max.

then i took a look in the owner's manual for my car, and it says this:

"A Tire and Loading information label is attached to the vehicle's center pillar, below the driver's door latch. This label lists your vehicle's original equipment tires and their recommended cold tire inflation pressures. The recommended cold tire inflation pressure, shown on the label, is the minimum amount of air pressure needed to support your vehicle's maximum load carrying capacity."

it doesn't say anything about what pressure to inflate if non-OEM tires are installed. But I would imagine that if I inflate my 44psi tires at 30 psi, it's going to cause excessive flex, heat, etc. and will reduce the life of my tires.

[ercchry]

Originally posted by nonlinear
s

it doesn't say anything about what pressure to inflate if non-OEM tires are installed. But I would imagine that if I inflate my 44psi tires at 30 psi, it's going to cause excessive flex, heat, etc. and will reduce the life of my tires.

...no

think of it like this.... a ballon can hold 44psi before exploding.... do you fill it to 30psi... or do you fill it right to the max of 44psi?

[nonlinear]

^^dude, the max inflation pressure if FAR from the blowout pressure. and you don't want inderinflated tires, either. this is from my manual:

NOTICE: Do not let anyone tell you that under-inflation or over-inflation is all right. it is not. if your tires fo not have enough air (under-inflation), you can get the following:

-too much flexing
-toomuch heat
-tire overloading
-premature or irregular wear
-poor handling
-reduced fuel economy

too much air:
-unusual wear
poor handling
-rough ride
-needless damage from road hazards.

since the car manufacturers recommendation is the "minimum PSI required to support the maximum load capacity," i conclude that I should run my tires near the maximum recommended by the tire manufacturer, as long as tire value > car value. i've been reading inflation arguments on other forums, too, and conclude this from reading there also.

[ercchry]

have you noticed what happens when you add heat to a tire? (think drag car doing a burn out)

tell me, if you set your pressure to the maximum when the tire is cold, will if not be over that maximum when heated?

EDIT: and minimum pressure for MAXIMUM load? do you often carry around that sort of weight?

[nonlinear]

Originally posted by ercchry
have you noticed what happens when you add heat to a tire? (think drag car doing a burn out)

tell me, if you set your pressure to the maximum when the tire is cold, will if not be over that maximum when heated?

yes, i understand what you are getting at (ideal gas law hehe) however, the max inflation given on the sidewall is a cold inflation value... i.e. the changes in gas volume with temperature are already accounted for.

and, if temp really is a concern, you should keep your tires near max inflation, since under-inflated tires get hotter than properly-inflated tires. actually, i had a leak in a tire on one of my old cars, and when i pulled in to a gas station the tire was so hot it was steaming (from snow)... the plys eventually separated from that tire, and i'm guessing it was due to damage from the excess heat.

Originally posted by ercchry

EDIT: and minimum pressure for MAXIMUM load? do you often carry around that sort of weight?

no i don't, but note that it's MINIMUM pressure. the car manufacturer doesn't say anything about maximum pressure... that depends on the tire design, which is why the tire manufacturer gives the max pressure.

[GTS4tw]

Originally posted by ercchry


...no

think of it like this.... a ballon can hold 44psi before exploding.... do you fill it to 30psi... or do you fill it right to the max of 44psi?

I don't usually agree with nonlinear, but wtf are you smoking? I fill to 5psi under on 44psi tires because I have found it to be optimal for fuel mileage and comfort, but I would be fully comfortable at max pressure. The tires will not blow up at 44psi (or 54 or 64.... but I digress) they will be quite hard and will lose grip on slippery surfaces, but there is no danger.

Also, on your other "fact" the max pressure is tested at COLD.

[ercchry]

yes.. there is minimums and there is maximums, why would you run either? you need a balance, if you do not you will get uneven tire wear... like so:

[nonlinear]

^^yes, however "proper inflation" in that diagram is the maximum inflation pressure given on the sidewall of the tire.

[ercchry]

Originally posted by nonlinear
^^yes, however "proper inflation" in that diagram is the maximum inflation pressure given on the sidewall of the tire.

i doubt it, you know why? i have ran many, many different tires, sizes, diameters, and brands... i have got the over inflated results at less then the maximum sidewall psi.... you would be amazed at how the traction levels drop on a regular passenger car tire around the 40psi mark

[89s1]

Much like the picture in his signature nonlinear must see everything as black & white.

I honestly don't see whats so hard to understand, but he has a hard time with lots of things that seem pretty logical to me...

[nonlinear]

oops

[nonlinear]

Originally posted by ercchry


i doubt it, you know why? i have ran many, many different tires, sizes, diameters, and brands... i have got the over inflated results at less then the maximum sidewall psi.... you would be amazed at how the traction levels drop on a regular passenger car tire around the 40psi mark

yea i've never worn through a set of tires enough to see the long-term wear patterns. but i've always ran at maximum recommended inflation.

i have yet to see a convincing argument of why to run below max inflation. i've also read quite a bit about why under-inflation is bad.

[89s1]

Inflating to maximum pressure leaves less room for expansion of the air as it comes up to temperature. Get it? Set it to max cold, it quickly goes above max when driving long distances or on a nice hot day.

[nonlinear]

Originally posted by 89s1
Much like the picture in his signature nonlinear must see everything as black & white.

I honestly don't see whats so hard to understand, but he has a hard time with lots of things that seem pretty logical to me...

dude, seriously, why do you always have to turn everything into personal attacks on my character? am i really being such an asshole, or such an idiot, that you have to constantly act like an 8th grader? grow up dude!

i'm an accurate and precise guy, and i want my tires inflated properly. i also want to know WHY i'm inflating to a given pressure. if it's too much for you, you don't have to read the thread. geez!