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

 

You are comparing normal (glove box) vs max. Right?

 

Glove box

 

ALWAYS the door jamb or glove box.

 

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

 

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

 

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

 

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.

 

No argument here. The better choice is to know what you are doing!

Matt