Best way to check tire pressure?

It is *IMPOSSIBLE* to accurately measure tire-pressure at a gas station... for that matter, anywhere you just drove to.

The reason is simple. Tire-Pressure should only be measured COLD.

Once you start driving, the air inside heats up. That causes the pressure to increase... which totally screws up your intentions. So you have no choice but to wait several hours for the tires to first cool down.

 

Tires have to be checked "cold", which means that the car has been driven no more than one mile in the hour before the tire pressure is checked. This is the condition under which the maximum rated pressure stated on the tire is determined. Pressure goes up many pounds with a little driving and makes a measurement meaningless. (The maximum rated pressure given on the tire accounts for this increase. A pressure measured immediately after a long drive may be greater than the stated maximum; that by itself does not indicate a problem.)

I measure mine at home in the morning, after the car has been sitting all night. I also have an air pump at home. Without that, one could note how many PSI/kPa need to be added to each tire and then drive to a service station and add those amounts.

 

I would use my own gauge and check them when they're cold (ie not many miles driven).

 

I think if you go to an auto parts store or a Wal-Mart or someplace like that you can pick up a pretty good tire pressure gage fairly cheap. I think it could be either analog or digital and you don't really care if it's dead on accurate or not, just so it's within a pound or two and is consistent.

Check your tires when they are cool, maybe in the morning before you drive the car and before the sun shines on one side for to long. I try to check mine every week and when I travel I take my gage along.

Just don't buy one of those pencil type things that you carry in your pocket, they are usually very inaccurate. If you get an analog one make sure it has a real gage on it.

 

<div class='quotetop'>QUOTE(aaf709 @ Jul 12 2006, 11:35 AM) [snapback]285024[/snapback]</div>

Auto Zone sells a nice digital gage for about 6 dollars. It holds the reading for the tire untill you reset it, so there is no guessing.

 

I use the Valve Lock that i bought from Sigma. $19 and its pretty accurate. Its a LOT better than that $.99 pencil gauge I bought a walmart.

ValveLock from Sigma

 

A decent digital backlit gauge that measures in 1/2 pound increments can usually be found for less than $10.00 at most places that sell auto parts. If you use that gauge every time you will at least have consistent variance between checks which is what is so important. Even digital gauges will often vary between each other.

 

I own a handheld digital pressure gauge (a la Walmart), and now own a second digital gauge that came with my new portable inflator. Both measure in .5 psi increments, but the difference in measurements between the two is 2 psi. Not sure which one to believe, so I just make sure I'm being consistant more than being "right."

 

<div class='quotetop'>QUOTE(brandon @ Jul 12 2006, 07:06 PM) [snapback]285262[/snapback]</div>

10-4, thats how it works. just use the same one each time and you will be fine.

 

As everyone else has said already, carry your own reference.
.
However, note that even a mile of driving does not heat tires all
that much, *especially* if you've already got them at good pressure
[sidewall pressure, NOT the door/glovebox/owners-manual BS]. Feel
them before you take off, go your half-mile or two miles or whatever
to the gas station, and feel them again. Remember, it takes about
TEN degrees F to make ONE psi of difference. Just having the car
sit with the sun on two out of four tires for a while will have a
much more profound effect than driving a short distance, and you
should try to take such environnmental factors into account when
you go to check your pressures.
.
_H*

 

This is from an old issue, but TIRE BUSINESS (a trade journal), September 2nd, 2002, had an article from a Consumer Reports ratings of tire gauges...

"Consumer Reports" magazine recently rated 8 tire gauges according to
accuracy, ease of use, readability and ruggedness. As TRIB has stated
before, gauges loose their accuracy if frequently dropped. Of these
gauges the AccuGauge H100X and Monkey Grip M8854 were knocked out of
calibration by an average of more than 5psi when dropped from a height
of 3 feet onto a hard floor, (ruggedness test) and rated as Fair. The
Pressure Inc. DT-105's digital "went blank for about 5 minutes and
then returned to normal." It was rated as Very Good.

BRAND & MODEL PRICE OVERALL SCORE
1. Accutire MS-4000 $30.00 Excellent
2. Accutire MS-4020B $15.00 Excellent
3. Monkey Grip M8867 $10.00 Excellent
4. NAPA 90-389 $ 8.50 Excellent
5. Monkey Grip M8862 $ 3.00 Very Good
6. Pressure Inc. DT-105 $11.00 Very Good
7. AccuGauge H100X $19.00 Fair
8. Monkey Grip M8854 $ 9.00 Fair


The prices have dropped since then. The #1 (actually the MS-4000B) is now only $9.

 

when i check my tires, it's in the morning when it's still somewhat cool outside before i go to work. if they need air, i mark down how much i need to put in each tire and stop at a gas station on the way to work if i have time, and on the way home if i'm running a bit late.

at the gas station, i take the current reading of the tire and add however many lbs of air the tire needs.

oh yes, and i use an analog gauge to take the readings.

 

In Australia, by law tyre repair/replacement garages have to have a master gauge. I had my gauge checked against their master and it was spot on. I have a small compressor so inflate my tyres at home.

 

<div class='quotetop'>QUOTE(john1701a @ Jul 12 2006, 12:34 PM) [snapback]285022[/snapback]</div>

After reading your great manual, John...I decided to go and get the tire pressure increased to at least 40/38...which I did...car wasn't cold and I'm a tire pressure dummy, so my mechanic did it.

I have the Campbell Hausfeld cordless inflator on order...that's the one you recommend. Is is easy to use??? Do you have to measure tire pressure with a separate gauge, or does the unit tell you you have...x amount of psi per tire???

Also, you recommended a tire guage...it was a Brookstone. They now advertise a new "smart pressure" guage...with three different colors...to alert need for fill (or empty) and it stores two different pressure memories (front and rear). Would you recommend this one?

When I get the portable inflator, can I plug it in to a standard outlet to recharge it's 12-volt battery? I assume you could also just plug it in and use it since one would most likely be changing tire pressure at home with "cold" tires...

Thanks!!

I just got 32,8 mpg on my first tank, 31 calculated, so I refilled, recorded this and reset MFD...right off the bat, my average is now above 40....was 60, but I do have lots of inclines to negotiate and do take very short trips, but have learned to combine errands so ICE stays warmed up and even to let car run in Park with power on instead of turning off, if I am just going to run into house....

Hope my second tank shows results of all I have learned so far from your manual!!!

I'm getting the coasting down, but sometimes I pick up so much speed I have to brake, and I'm trying to save some to get started on the next incline...also "dead-screening" a bit as well on some flats....

LOVE my PRIUS! It says 51 mpg...but I'll be happy if I go above 40...since I use E10 and drive very short 5 minute trips...some are 10-15, and am trying to combine errands.

So...Hopefully, I will get this tire pressure thing working for me as well.

P.S. Not the best photo, but my avatar is a digipix I took this morning of my car.....

terri

 

I always check my pressure when cold. I don't look at the sidewall either because I am not going to blow $$ on tires. Mine are set 32 for the front and 35 rear on both cars.

I wont go into the sidewall number because it is like talking to a wall with many of you. If you want to run your tires at the MAXIMUM pressure, that's your choice. I will run mine at a safe limit that has allowed me to get 36k+ out of my tires.

 

<div class='quotetop'>QUOTE(Blackfang @ Aug 6 2006, 08:18 PM) [snapback]298773[/snapback]</div>

The usual recommended pressure is 2 pounds greater in the front. The door sticker says 35 front, 33 rear, and some people use higher pressure.

 

<div class='quotetop'>QUOTE(Blackfang @ Aug 6 2006, 08:18 PM) [snapback]298773[/snapback]</div>

OEM tires on the prius are crap... using toyota's pressure ratings wears them out pretty quickly.

 

Coming out of my driving, I have a VERY steep, short incline to get to the top of a hill....

In winter, my Camry was great with Blizzaks or similar tires and the front wheel drive.

I will see how the Integrities perform this winter since I have them, but I am keeping my tire pressures at 40/38....maybe even a bit higher when I get my portable 12 volt tire inflator, since the increase I had was done after the car had run some.

I plan to replace them with wider tires when the time comes, so might as well inflate now and see how my winter goes and my mileage.

terri