Tire Pressure?

[jerr529]

I have on star and i rec once a month report on my truck it seems i have evry month a 2 lb loss from tires i check regularly and i have a Accue tire pressure gage and my tires tell me that im 35 to 36 lbs,Is it possiable that you can lose a lb of pressure over a months period// I also have the DEC and that never reads righyt lol.Anyone have problems like this and is it normal too lose pressure over a months time??

gerard

[dlstewart01]

Since air is a gas, it expands when heated and contracts when cooled. In most parts of North America, this makes fall and early winter months the most critical times to check inflation pressures...days are getting shorter...ambient temperatures are getting colder...and your tires' inflation pressure is going down!

 

The rule of thumb is for every 10° Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower).

 

In most parts of North America, the difference between average summer and winter temperatures is about -50° Fahrenheit...which results in a potential loss of about 5 psi as winter's temperatures set in. And a 5 psi loss is enough to sacrifice handling, traction, and durability!

 

Additionally, the difference between cold nighttime temperatures and hot daytime temperatures in most parts of the country is about 20° Fahrenheit. This means that after setting tire pressures first thing in the morning, the vehicle's tire pressures will be almost 2 psi higher when measured in the afternoon (if the vehicle was parked in the shade). While that is expected, the problem is when you set your vehicle's tire pressures in the heat of the day, their cold pressures will probably be 2 psi low the following morning.

 

And finally, if the vehicle is parked in the sun, the sun's radiant heat will artificially and temporarily increase tire pressures.

 

We put some of these theories to the test at the Tire Rack. First, we mounted two tires on wheels. We let them sit overnight to equalize and stabilize their temperatures and pressures. The following morning we set them both to 35 psi. One tire and wheel was placed in the shade while the other was placed directly in the sun. We then monitored the ambient temperatures, tire temperatures and tire pressures through the day. As the day's temperatures went from 67° to 85° Fahrenheit, the tire that was kept in the shade went from our starting pressure of 35 psi to a high of 36.5 psi. The tire that was placed in the sun and subject to the increase in ambient temperature plus the sun's radiant heat went from our starting pressure of 35 psi to a high of 40 psi. In both cases, if we had set our tire pressures in the afternoon under the conditions of our evaluation, they would have been between 2 and 5 psi low the following morning.

 

Next we evaluated the affects of heat generated by the tire's flexing during use. We tried to eliminate the variable conditions we might encounter on the road by conducting this test using our "competition tire heat cycling service" that rolls the tires under load against the machine's rollers to simulate real world driving. We monitored the changes in tire pressure in 5-minute intervals. The test tires were inflated to 15 psi, 20 psi, 25 psi and 30 psi. Running them all under the same load, the air pressure in all of the tires went up about 1 psi during every 5 minutes of use for the first 20 minutes of operation. Then the air pressures stabilized, typically gaining no more than 1 psi of additional pressure during the next 20 minutes. This means that even a short drive to inflate your tires will result in tires that will probably be under-inflated by a few psi the following morning.

 

Add all of these together, and you can understand why the conditions in which you set your vehicle's tire pressures are almost as important as the fact that you do set it.

 

It's important to remember that your vehicle's recommended tire pressure is its cold tire inflation pressure. It should be checked in the morning before you drive more than a few miles, or before rising ambient temperatures or the sun's radiant heat affects it.

 

And by the way, if you live in the North and park in an attached or heated garage you will lose pressure when you leave its warmth and venture into the real world outside during winter. Add 1 psi cold pressure tire pressure to compensate for each 10° Fahrenheit temperature difference between the temperature in the garage and outside.

 

And you will loose some air pressure over time.

•It’s possible for a passenger tire initially inflated to 35 psi (pounds per square inch) to lose 1 psi each month.

[jerr529]

Stew thanks for that responce,i gather its no big deal i inflate my tires to 35psi accoring to my accure tire gage.Its been a crazy month here in NY some days this month we hade in 70 then below 20 other days a really flux in the temps.So now 3 tires at 32psi ill pump up again to 35psi and see what happens after a week I have the same Veh as you ,I was worried i had leaks??

thanks

gerard

[700 sportsman]

I would reset the TPMS for a more accurate reading in the DIC

[jhbrennan]

I would reset the TPMS for a more accurate reading in the DIC

TPMS adjusts itself for psi fluctuations - not sure how you reset for more accurate reading??

[trucc_boi]

whats the difference between running 40psi vs. 35psi vs 30psi.. or even higher than 40psi if your tires are rated that high.

[dlstewart01]

whats the difference between running 40psi vs. 35psi vs 30psi.. or even higher than 40psi if your tires are rated that high.

 

The Maximum pressure listed on the tire, is just that, a maximum pressure that the tire can handle. That does not mean that you should run that pressure in normal load and driving. The auto manufacturer sets the pressure you should use for every day driving. If the tires are under inflated, they will ware out on the edges. Overinflated, they will ware out in the center. The only time the max pressure should be used is when you are at max load.

[ken1mod]

Gentlemen,

 

Tires must be inflated according to the load they carry. Load range E tires (75 psi max on sidewall) should be inflated to 30 if they only carry 800 lbs. These charts are all over the internet. Overinflation can definitely be achieved below the sidewall max. Check the tire manufacturers sites.

 

Over inflated tires handle rotten, stop rottten and wear out the center of the tread fast. Sometimes it is useful to check the tire print after a short rain on a driveway. Full contact is what you want.

 

Also, this is why the sticker on the drivers door is often less than the max sidewall pressure. Further, we rarely load our trucks to capacity.. My silvy loves just 25 psi in the rear tires because I never really load it.

 

Ken

[700 sportsman]

I would reset the TPMS for a more accurate reading in the DIC

TPMS adjusts itself for psi fluctuations - not sure how you reset for more accurate reading??

 

 

Do a search on here for TPMS Calibration, it involves putting truck into "learn mode", and then letting air out of each tire (in a certain patter) until the horn chirps