A "little accurate" eh? Mazda is one who ships their cars with higher than the pressure listed on the door placard. Again, this has been discussed many times in the various forums. Always a good idea to check and make sure the tires have been adjusted as soon as you get home (or better yet before you leave the dealer).

 

Here's a question for you guys. Ok, let's say it's 20 degrees outside in the morning. You set your tire pressures accordingly. You drive around a bit, then go home/work for some hours. So, it's now 2pm in the afternoon and the temps are ~ 40 degrees outside. Does anyone/should you readjust the tire pressures to accommodate that rise in ambient temperature?

 

No leave them as you adjusted them originally.in the morning with NO sun on the tires. Any normal raises and difference in tire pressure usually will affect tire/air pressure at higher ambient temperatures or very spirited driving on dry roads. The other reason is during driving even in colder ambient temperature you may raise the temperature on the drive wheels/tires (front) because of some situations where continual and constant braking is done. The braking will heat the wheels which raises the air temperature in the tire which rases the tire pressure. If you have a TPMS that reports in 1-degree increment changes in tires pressures, you can confirm that there is little change in colder driving conditions except as I mentioned.

 

In an ideal world, yes you would adjust pressures according to ambient temps, but in reality who is going to take the time to do this on a daily basis?

 

Thanks, Callisto and chickdr19.

 

I think you miss learning points, FACT you should always adjust the proper tire pressure shown in the auto manufactures tag in the door jam, the best time early morning before any traveling is done with no direct sun on any of the tires. Once this is done if you have no punctures in the tire or leaking wheel/rims and Schrader valve is in good condition with a cap and O-ring sealing properly your tire pressure should maintain the proper tire pressure for months!

I just went into a little more detail explanation that went right over your head.

ASE

 

It's good practice to check tire pressures under consistent conditions, such as Callisto said. That way you remove most of the causes of pressure variance caused by temps and you'll get a better indication over time of how well your tires are holding pressure.. I set my tires maybe 1 lb higher than spec'd to compensate for slight leakage, better to be slightly over than under. Also, get a tread depth gauge, places like Discount Tire will give them to you, and measure all the groves on the tires to make sure the tires are wearing evenly. If wearing more in the center, then pressure too high. Wearing more on the edges, pressure too low. Tire chalk will help you monitor tire "roll". Then youll find the ideal pressure for your tires on your car driven the way you drive.

On the track I would check frequently and adjust in 1/2 lb increments until I found the proper setting for the day, and then adjust before every run. For events like autox we ran lower pressure as the tires would head up quickly and on long tracks ran at a higher pressure to minimize sidewall flex and roll-over. Always used tire chalk to check the roll-up on the side of the tread to make sure I was using all of the tire tread. And happier when I used up the tread faster as that meant the car was pushing it's limits :-)

 

Many people think that the outside temperature has more effect on tire pressure than it really does. The rule of thumb that I recall is that tire pressure will vary about 1 psi for every ten degrees of variation in air temperature. Tire pressure will vary more by the tire heating up as you drive than by ten or 20 degrees of change in air temperature. That's why Callisto's advice is good as it provides consistency. Otherwise, you would be checking and changing pressures every time you get in the car to try to keep a consistent temperature. The engineers realize this when they recommend a tire pressure and the changes in psi are factored into calculating the recommended pressure.

As AZCX5 mentioned, there are times to vary this procedure, such as on the track, but for most drivers and most situations, that is not the best way to proceed. If the air temperature is increasing or dropping 40 or 50 degrees, it's a good idea to check and adjust the pressures while the tires are cold and not adjust them again until the tires are good and cold which takes several hours after you quit driving.

 

Agree, check tire pressure when tires cold. What can throw off readings is when one side of the car has been in direct sunlight all day, those tires willl read slightly higher than the shady side. Esp in the AZ sun!

 

I hear you. I've spent a lot of time in that state - broiling in the summer in the southern part and freezing in blizzards around Flagstaff in the winter.