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Old 04-01-2013, 01:47 PM   #1
Acrown
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Tire Pressure

I have a 2013 Silvarado 2500HD that I use to pull my 2008 Fuzion 393 toy hauler. The truck has a TPM system that shows me tire pressure. I always check tire pressure before each trip. On our last trip, I noticed the rear tire pressure getting close to 90psi as we were on the freeway. I had set them to about 78 PSI before the trip (Chevy says it should be 80psi).

My questions are...
1) How high can it go before I should stop and do something about it (e.g., 90, 95, ???)

2) What should I do when it reaches that max tire pressure (e.g., stop and remove some air pressure, stop and wait to cool down, etc).

I have only been towing since the start of the year so any help is greatly appreciated. Thanks
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Old 04-01-2013, 02:09 PM   #2
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Quote:
Originally Posted by Acrown View Post
I have a 2013 Silvarado 2500HD that I use to pull my 2008 Fuzion 393 toy hauler. The truck has a TPM system that shows me tire pressure. I always check tire pressure before each trip. On our last trip, I noticed the rear tire pressure getting close to 90psi as we were on the freeway. I had set them to about 78 PSI before the trip (Chevy says it should be 80psi).

My questions are...
1) How high can it go before I should stop and do something about it (e.g., 90, 95, ???)

2) What should I do when it reaches that max tire pressure (e.g., stop and remove some air pressure, stop and wait to cool down, etc).

I have only been towing since the start of the year so any help is greatly appreciated. Thanks
If you will take a closer look at the tires, the max inflation pressure is a cold inflation, not a hot one. Tire manufacturers know that the pressure will increase when the tires warm up, but they want you to check the pressures when the tire is cool, usually around 70F if possible. By doing that, the tire is also properly inflated when it warms up as you drive. To my knowledge, there is no max hot inflation number so you do nothing when the tire warms up except keep on driving.

Most tire manufacturers have extensive information on tire inflation on their websites. I encourage you to do your own research and learn as much as you can.

One exception you should understand. If ONE tire gets a lot hotter than the others, pull over ASAP. Without touching the metal, check to see if the wheel on that tire is really hot compared to the others. If it is, it is usually a sign of trashed bearings or brakes.
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Old 04-01-2013, 02:27 PM   #3
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The tire should not gain more than 20% unless there is a condition present. That condition could be as simple as speed.


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Old 04-01-2013, 02:27 PM   #4
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A couple of additions here. Check the manufacturers inflation charts for your truck tires. You will see that their load bearing rating is directly related to tire pressure. The lower the pressure, the lower the weight rating. That tire pressure is set cold. Now here's the kicker: An under-inflated tire with too much weight on it will get hotter than a properly inflated one because there is more flex in the side walls and tread. This is what leads to almost all premature blowouts.

If you are towing, you want the max load bearing capacity possible so you inflate the tires to their max cold pressure. The extra weight is then properly supported by the tires. Many of us will drop the pressure on E rated truck tires when not towing to soften up the ride a bit. That seems to be OK as we're not carrying the extra weight associated with towing or hauling. On my '02 Dodge 3500 dually, I ran 80 psi when towing but knocked the rears down to 60 psi otherwise. There was no perceptible difference in tire wear, but my backside appreciated it immensely.
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Old 04-01-2013, 02:34 PM   #5
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The tire should not gain more than 20% unless there is a condition present. That condition could be as simple as speed.


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If that occurs, the first culprit to consider is under inflation. A properly inflated truck tire should handle normal highway speeds without issue unless traveling in unusually hot weather. An under inflated tire will get excessively hot even in cool weather conditions.
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Old 04-01-2013, 02:37 PM   #6
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If that occurs, the first culprit to consider is under inflation. A properly inflated truck tire should handle normal highway speeds without issue unless traveling in unusually hot weather. An under inflated tire will get excessively hot even in cool weather conditions.
Amen. Under inflation and speed is a terrible combination.


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Old 04-01-2013, 02:56 PM   #7
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Amen. Under inflation and speed is a terrible combination.


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I believe it has an official name too. Ford Explorer Syndrome.
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Old 04-01-2013, 03:02 PM   #8
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The tire should not gain more than 20% unless there is a condition present. That condition could be as simple as speed.
He set his pressure to 78. 78 +20% is around 94. I'm not sure there is an issue as long as both rears are reaching the same pressure.

But I don't have the sensors so am not really sure what pressures mine reach when warm. I run about 75 cold when towing.
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Old 04-01-2013, 04:59 PM   #9
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I use the sensors on my trailer but not my truck. It has been common for me to start out at 65psi and reach 75psi on all four tires. 20% would be 78psi. And to Steve's point, under inflation is a major contributor to excessive heat build up. The point that I was trying to make was in conjunction to his, that speed, in addition to low air pressure, is a disaster waiting to happen, especially with heavy weight thrown into the mix.


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Old 04-03-2013, 11:37 AM   #10
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Originally Posted by SteveC7010 View Post
If you are towing, you want the max load bearing capacity possible so you inflate the tires to their max cold pressure. The extra weight is then properly supported by the tires. Many of us will drop the pressure on E rated truck tires when not towing to soften up the ride a bit. That seems to be OK as we're not carrying the extra weight associated with towing or hauling. On my '02 Dodge 3500 dually, I ran 80 psi when towing but knocked the rears down to 60 psi otherwise. There was no perceptible difference in tire wear, but my backside appreciated it immensely.
Steve,
Ditto here too for my F350 when I ran brand new tires Costco said they had to inflate them to 80 psi... well it caused the new tires to wear wrong and cup... so I too drop them down to about 60 on the rear while not towing.
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Old 04-03-2013, 12:07 PM   #11
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Steve,
Ditto here too for my F350 when I ran brand new tires Costco said they had to inflate them to 80 psi... well it caused the new tires to wear wrong and cup... so I too drop them down to about 60 on the rear while not towing.
Exactly! Too much pressure and not enough weight means the center of the tread will bulge just enough to cause all kinds of handling, ride, and tire wear problems. The manufacturer's load charts are designed, in part, to prevent over inflation as well as under inflation.
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Old 04-03-2013, 07:06 PM   #12
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I can't find disagreement with the statements posted. It makes no sense with a empty truck to run 80 psi and putting only the center of the tire on the roadway. Because that is all that is in contact if you look. I air up to pull/haul 65 to 80 psi and back down to 55 or 60 psi when empty. The tire will last longer but, more important the truck drives better. Better stopping, cornering etc. easier on your back. On police trucks I was issused, 4 total, the install guys always took off the factory tries and put on 10 plys with 80psi. I had to drop them down to 60 on the 1/2 tons and 65 on 3/4 ton. They were unsafe to drive as a police vehicle with that much air. The 3/4 had to haul a 8,000lb boat so 65 was the best since I did not have time to air up/down tires. It also had tire senors and the yellow warning light remained on for the 18 months I had it.
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Old 04-08-2013, 12:28 PM   #13
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“Generally, as a radial tire revolves during operation, heat is generated on the inside of the tire at 4 degrees per minute. However, the tire loses heat at the rate of 3 degrees per minute with dissipation throughout the casing and airflow around the tire. After 40 minutes of continuous operation, the temperature has increased 40 Fahrenheit. As the temperature inside the tire increases, the inflation pressure also increases. Thus, a tire inflated to 80 psi cold would now be 85 psi. Because the inflation pressure has increased , the amount of tire flexing has decreased, which decreases the amount of heat generated per minute to 3 degrees per minute. Assuming the heat dissipation factor is still 3 degrees Fahrenheit per minute, the net temperature change is nil (0). This is called Thermal Equilibrium.”

I’m not a tire engineer. That quote came from the Michelin truck tire maintenance manual.

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Old 04-08-2013, 12:59 PM   #14
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I’m not a tire engineer. That quote came from the Michelin truck tire maintenance manual.

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Old 04-09-2013, 07:28 AM   #15
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My questions are...
1) How high can it go before I should stop and do something about it (e.g., 90, 95, ???)
Rase your starting pressures 2 or 3 psi.
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Old 04-11-2013, 02:45 PM   #16
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Well here is my 2 cents worth. 2004 3/4 Chevy Avalanche with a 8.1L engine LT tires over 50,000 miles on the tires 8/32's of tread left just drove to Gulf Shores Alabama from Indiana 12 hour drive each way. I always run 50psi when not towing. And add 30psi when pulling my 08' Keystone Passport. So 50 psi up front all the time and 80psi when towing. Perfect combo.
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Old 04-12-2013, 08:36 AM   #17
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The correct tire pressure for your auto, truck or SUV can be found on its tire placard or in the owner’s manual. The owner’s manual will also have information for special circumstances such as towing.

Here is a reference that explains all that stuff.

http://www.safercar.gov/Vehicle+Shop...al+Information

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