# Thread: Car air pressure

1. ## Car air pressure

Does it matter what time of day, or the temp on when i fill my tires?? Filled them 2day at 3pm and its like 60 out. Didn't fill them max cause i had 2 gauges, didn't know which one was accurate, didn't wanna over inflate

2. Generally you want to avoid filling to the limit in high heat....because if you fill your tires to say 30psi....on a hot day, then fly down the highway...which is getting baked by the sun..so is even hotter....then the tires will substantially heat up....then take a psi reading....you'll find it way higher.

So best to check your tire pressure after driving a bit...and factor in some heat changes if it's middle of an icy winter....or middle of a hot summer day.

3. its best to check and fill your tire pressure without having ridden on them very much

in fact you should actually check them before you even leave your driveway...

when you ride on the tires it heats em up, which causes the air to expand and give false readings about the pressure

4. Your car manual most likely says check your tires after not being driven on for THREE HOURS. also it says to fill them up at that time too, kinda hard to do that at a gas station i guess eh?

Best to check it at normal room temperature.. say like 60 - 75

5. Very interesting. I was wondering this myself. I find I get different readings before and after driving.

6. Originally posted by mikemean
Very interesting. I was wondering this myself. I find I get different readings before and after driving.
Yeah, that's what I was getting at. You have to use your head, and a little common sense will let you adjust to why the readings are different. Take the psi when they're cold....and if you fill them to the very limits when cold...then drive high speed....the pressure will be up past the limits of the tire.

Measure the tire after driving for long periods, you'll find the psi past the limit...and will have a tendancy to think "too high, I better let some out"...then you'll let some pressure out...now when the tires are cold you'll take a psi and find it way below.

See how the game goes? That's why it's really just common sense...if it's a hot day, and you've driven for a while, realize the psi will be a bit higher. If it's cold out, and you haven't left your driveway....realize the psi will be a low reading. Which brings me to my warning...filling up cold tires can lead to them getting overinflated too easily once you get driving. Which is why I prefer to check them accurately after "driving a bit"....short distance.

7. ok, thought soo... My lumina was at 25psi filled to 35

Passat was at 30psi, after driving on it, let it cooled for 10 mins filled to 35 psi

Found out my lumina was very very low on oil.. lucky for me to check

8. Here is an article that I found on the internet pertaining to this thread:

Do It While They're Cold!

Tires need to have air pressure checked regularly but it must be done while the tires are COLD!
All tires should have their air pressure checked on a regular basis, preferably weekly for truck tires and at least once a month for passenger car tires.

Truckers and motorists who get in the habit of checking their tires on a regular schedule will experience far fewer tire failures and, as an added benefit, will find that their tires last longer and their fuel costs will decline.

"One of the problems about tires is that they are practically the only part of a vehicle that can be totally abused and the vehicle will keep moving. Seriously underinflated tires will not stop a vehicle. Try driving with no brakes and you'll see what I mean," said Harvey Brodsky, Managing Director of TRIB, the Tire Retread Information Bureau. "Because of this, many truckers and motorists tend to ignore their tires, often until it's too late."

"By not paying attention to this very important component of tire care, they not only waste money, but they put themselves and others at risk of an unnecessary tire failure," Brodsky added.

TRIB recommends setting a regular weekly or monthly schedule for checking air pressure. A properly maintained and regularly calibrated tire gauge should be used, and the tires MUST have their air pressure checked while the tires are
COLD, preferably having been driven for less than one mile.

The retreadability of truck tires that have never been driven underinflated rises dramatically, which has a very positive effect on a trucking fleet's bottom line. The best way for fleets and motorists to lower tire costs is to inspect tires regularly for cuts and other signs of irregular wear, and to check tires with a gauge while the tires are COLD.

A good time to check tires is first thing in the morning after the vehicle has been sitting for several hours or longer. This will insure that the tire inspections and air pressure checks are being made while the tires are COLD.
According to TMC data it only takes about 20 minutes to check and adjust inflation pressure on an 18 wheeler.

The old saying, TAKE CARE OF YOUR TOOLS AND YOUR TOOLS WILL TAKE CARE OF YOU is especially true when it comes to tires.

Tires are tools (try operating a vehicle without them!) and whether we like it or not, they do require care.

The time it takes to visually inspect and maintain proper air pressure in tires is an investment that fleets and motorists really can't afford not to make.

9. This is another statement I found on another site:

Remember, the tire inflation number that vehicle manufacturers provide reflects the proper pounds per square inch (psi) when a tire is cold.

To get an accurate tire pressure reading, measure tire pressure when the car has been unused for at least three hours.

10. ...and one last one

Checking Tire Pressure

Check your tire's air pressure at least once a month, using a good quality pocket-type gauge. You can't "eyeball" tires accurately-radial tires can look fine even when they're underinflated.

To check your tires' air pressure:

Make sure the tires are cold ... their pressure rises when you drive. After removing the cap from the valve stem, press a tire gauge onto the valve stem and check the reading. Add air to reach the correct tire pressure. If you overfill, release air by pressing the metal stem in the valve's center. Make sure you replace the valve cap.

Don't forget to check your spare.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•