Tire Pressure Confusion

Hi,
My sister-in-law owns a 2003 Hyndai Accent. I check the tire(s) pressure, etc. for her. Tires are P175/70R13 if I remember right. On the tire sidewalls, "normal load", the max PSI is "44 LBS", but in the
glove box, a label for tire pressure states 30 !!!
A newspaper article I read recently states to use the information on the sidewalls for proper tire pressure. However, my brother read an article that recommends using the information on the car door jam or glove box.
Does anyone know for sure what is the proper reference for tire pressure?
Thank You in advance, John
PS, Remove "ine" from my email address
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You are comparing normal (glove box) vs max. Right?

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Glove box
snipped-for-privacy@verizon.net wrote:

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ALWAYS the door jamb or glove box.
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Ed Pawlowski wrote:

Not necessarily. The car maker's recommendation is a compromise pressure that gives some combination of ride quality, handling and fuel economy that someone at the car maker thought was the "best" compromise. It may not be the best for you. I prefer to err on the side of best fuel economy so I generally run higher than what is recommended, realizing that I sacrifice some ride quality in doing so. As long as you don't go below the car maker's recommendation (this could compromise the load capacity of the tire for your vehicle) nor above the tire maker's maximum rating, you are fine. EXperiment until you find a pressure that is the right compromise for you. For my Sonata, I run 32 psi.
This is less than the max allowed (I believe my current tires have a max of 35), but more than Hyundai's recommendation of 30. My Chrysler minivans run best at 35, which is well above the Chrysler recommendation which I forget at the moment, but I think is in the 28-39 range. These vans are heavy and I find better performance and handling with the tires at the max allowed pressure. Some used to claim that higher pressures adversely affected performance, braking in particular, but tests I've seen don't support that. Handling and braking are generally better at or above 30 psi and often keeps getting better right up to 35. Higher pressures also raise the speed at which hydroplaning will occur.
http://www.nhtsa.dot.gov/Cars/rules/rulings/TirePresFinal/FEA/TPMS3.html
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In the case of my Infiniti, which I have no idea of what tires came originally, the glove box says 29 lbs. I have noticed low-pressure wear and increased to the tire sidewall of 35, however the ride is stiff. I believe I'll knock down to 32.
This has been an argument I've had with tire shops for 20 years. Some say one, the others say the tire. It all goes back to what cam with the vehicle originally IMHO.
Steve
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wrote in message

That may be true, but for someone unfamiliar enough that they don't know where to look, proper adjustment for their condition is probably out of the question. The tire maker certainly does not know what car the tire will end up on or the conditions you drive under so go by the car maker's recommendation unless you know what you are doing.
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Ed Pawlowski wrote:

No argument here. The better choice is to know what you are doing! :-)
Matt
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snipped-for-privacy@verizon.net wrote:

Read what the tire says. It says MAXIMUM pressure, not recommended pressure. The tire sidewall is a limit, not a recommendation. The owners manual and placards on the vehicle are recommendations.
I personally run my pressures on the high side, but generally not to the maximum value allowed by the tire maker.
Matt
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