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Old 04-07-2019, 05:06 PM   #1
swj
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max air pressure

Ford F150 SCrew, max tow pkg, 20 " tires. Towing 7000 lbs trailer.
Truck has Michelin 275/55/R20 LT, tire has max PSI 44 on sidewall.
Run 35 PSI as daily driver and inflate to 44 PSI when towing?
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Old 04-07-2019, 05:31 PM   #2
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Thats what most folks do. At least the back tires at max cold psi. Front can run a little less.
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Old 04-08-2019, 10:07 AM   #3
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max psi

Michelin says 35 psi as printed on door jam, ford dealer says 35psi for all four tires, 35psi is based on fully loaded truck with payload of 1732.
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Old 04-08-2019, 10:15 AM   #4
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Quote:
Originally Posted by swj View Post
Michelin says 35 psi as printed on door jam, ford dealer says 35psi for all four tires, 35psi is based on fully loaded truck with payload of 1732.
Correct. Nothing wrong with going to 44 if you find it helps a little.
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Old 04-08-2019, 11:08 AM   #5
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The tire's max load rating is achieved at the PSI listed on the door tag. Adding more air will not help carry more weight, but it may help eliminated some of the "wobbly" feeling reported when trailer is at full weight. Perfectly safe to put more in and see if you like it better.
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Old 04-08-2019, 11:11 AM   #6
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I don't give the door sticker for tire pressure much credence. They are usually either good for non-towing, towing, or neither.

Good example is my current truck. Max cold psi is 80 on the tire. Door sticker says 55psi front, 80psi back. At 55psi the fronts look flat (heavy diesel), handling and steering is just bad. 80psi for rear is great for towing, terrible for ride when not towing. This door sticker makes no sense to me.

So when not towing I run 65psi front, 60-65 rear. When towing I run 70 front, 80 rear.

You will get lots of opinions on what is correct. I'm just telling you what I do. Pick a psi that works for you and your situation (loaded, unloaded). Somewhere between door sticker and tire max cold psi is a good starting place.
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Old 04-08-2019, 11:14 AM   #7
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Originally Posted by NMWildcat View Post
I don't give the door sticker for tire pressure much credence. They are usually either good for non-towing, towing, or neither.

Good example is my current truck. Max cold psi is 80 on the tire. Door sticker says 55psi front, 80psi back. At 55psi the fronts look flat (heavy diesel), handling and steering is just bad. 80psi for rear is great for towing, terrible for ride when not towing. This door sticker makes no sense to me.

So when not towing I run 65psi front, 60-65 rear. When towing I run 70 front, 80 rear.

You will get lots of opinions on what is correct. I'm just telling you what I do. Pick a psi that works for you and your situation (loaded, unloaded). Somewhere between door sticker and tire max cold psi is a good starting place.
^^This^^ is my mode of operation as well.
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Old 04-08-2019, 11:18 AM   #8
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Just a FYI. My first sentence was a fact. Everything after that was an opinion.
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Old 04-08-2019, 12:22 PM   #9
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Quote:
Originally Posted by alb2tpa View Post
The tire's max load rating is achieved at the PSI listed on the door tag. Adding more air will not help carry more weight, but it may help eliminated some of the "wobbly" feeling reported when trailer is at full weight. Perfectly safe to put more in and see if you like it better.
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Originally Posted by alb2tpa View Post
Just a FYI. My first sentence was a fact. Everything after that was an opinion.
Sorry, you're incorrect or misstated what you were trying to say.

The TRUCK'S max load rating can be achieved at the PSI listed on the door/pillar tag, meaning the factory tires can carry the truck's GVWR/GAWR at the PSI listed on the truck's tag. The TIRE'S max load rating is achieved at the PSI listed on the tire.

The TRUCK tag PSI has nothing to do with the TIRE'S MAX load rating. The tires absolutely can carry more weight if more pressure is added above the truck's tag PSI (provided the tag PSI is not the same as the tire's max load PSI) but that does not increase the TRUCK'S load capacity.
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Old 04-08-2019, 12:40 PM   #10
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Very similar to what I did with 1500 Silverado and old Jayco. Close to the same weight..
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Old 04-08-2019, 01:10 PM   #11
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Sorry, you're incorrect or misstated what you were trying to say.

The TRUCK'S max load rating can be achieved at the PSI listed on the door/pillar tag, meaning the factory tires can carry the truck's GVWR/GAWR at the PSI listed on the truck's tag. The TIRE'S max load rating is achieved at the PSI listed on the tire.

The TRUCK tag PSI has nothing to do with the TIRE'S MAX load rating. The tires absolutely can carry more weight if more pressure is added above the truck's tag PSI (provided the tag PSI is not the same as the tire's max load PSI) but that does not increase the TRUCK'S load capacity.

SO... I talked to Michelin and my Ford Dealer, the max 35 PSI on door jam is the correct air pressure based on the truck being loaded at the full payload weight of 1732 llbs which is also on the door jam... I am going to leave my air pressure at 35PSI.
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Old 04-08-2019, 01:26 PM   #12
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Quote:
Originally Posted by swj View Post
Sorry, you're incorrect or misstated what you were trying to say.

The TRUCK'S max load rating can be achieved at the PSI listed on the door/pillar tag, meaning the factory tires can carry the truck's GVWR/GAWR at the PSI listed on the truck's tag. The TIRE'S max load rating is achieved at the PSI listed on the tire.

The TRUCK tag PSI has nothing to do with the TIRE'S MAX load rating. The tires absolutely can carry more weight if more pressure is added above the truck's tag PSI (provided the tag PSI is not the same as the tire's max load PSI) but that does not increase the TRUCK'S load capacity.

SO... I talked to Michelin and my Ford Dealer, the max 35 PSI on door jam is the correct air pressure based on the truck being loaded at the full payload weight of 1732 llbs which is also on the door jam... I am going to leave my air pressure at 35PSI.
*sigh* They have to say that. Sounds like you made a decision, so that's good. See how it feels while towing, experiment a little. Good thing is, you can always change your mind later; or not
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Old 04-08-2019, 01:26 PM   #13
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Quote:
Sorry, you're incorrect or misstated what you were trying to say.

The TRUCK'S max load rating can be achieved at the PSI listed on the door/pillar tag, meaning the factory tires can carry the truck's GVWR/GAWR at the PSI listed on the truck's tag. The TIRE'S max load rating is achieved at the PSI listed on the tire.

The TRUCK tag PSI has nothing to do with the TIRE'S MAX load rating. The tires absolutely can carry more weight if more pressure is added above the truck's tag PSI (provided the tag PSI is not the same as the tire's max load PSI) but that does not increase the TRUCK'S load capacity.



Quote:
Originally Posted by swj View Post
SO... I talked to Michelin and my Ford Dealer, the max 35 PSI on door jam is the correct air pressure based on the truck being loaded at the full payload weight of 1732 llbs which is also on the door jam... I am going to leave my air pressure at 35PSI.
Again... don't miss the fact (as DieselDrax eloquently pointed out) that the TIRES can carry more load than the door sticker says as verified by the 44 PSI MAX inflation. That doesn't mean the TRUCK can... but it also doesn't mean that adding air to the TIRES stated MAX inflation point (on the sidewall) will hurt the tire in any way.
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Old 04-08-2019, 03:52 PM   #14
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From tirereview.com

They also set each tire’s “load curve,” which is the relationship between inflation pressure and the tire’s maximum load carrying capacity. Like the size standards, there are some slight variations among the different organizations’ load curves, but they are not significant.
Part of each load curve standard is the point at which the load curve stops going up. For TRA p-metric standard load tires, it is at 35 psi. Equivalent ETRTO and JATMA tires peak at 36 psi. Interestingly, all of the standardizing organizations agree that standard load passenger car tires can (and should) use optional higher inflation pressures (44 psi or 51 psi) for certain circumstances such as high speed driving. However, these higher inflation pressures generally provide no increase in load carrying capacity and in some circumstances specify a reduction in load for high speed driving.

Since the OP has a P metric tire, just like I do, the FACT is, he has no more load carrying capacity at 44 or 51psi than he does at 35psi.
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Old 04-08-2019, 04:12 PM   #15
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Quote:
Originally Posted by alb2tpa View Post
From tirereview.com

They also set each tire’s “load curve,” which is the relationship between inflation pressure and the tire’s maximum load carrying capacity. Like the size standards, there are some slight variations among the different organizations’ load curves, but they are not significant.
Part of each load curve standard is the point at which the load curve stops going up. For TRA p-metric standard load tires, it is at 35 psi. Equivalent ETRTO and JATMA tires peak at 36 psi. Interestingly, all of the standardizing organizations agree that standard load passenger car tires can (and should) use optional higher inflation pressures (44 psi or 51 psi) for certain circumstances such as high speed driving. However, these higher inflation pressures generally provide no increase in load carrying capacity and in some circumstances specify a reduction in load for high speed driving.

Since the OP has a P metric tire, just like I do, the FACT is, he has no more load carrying capacity at 44 or 51psi than he does at 35psi.
The OP does not have a P-metric tire, they have an LT tire. Also, Michelin specifically states that max load for a 275/55/R20 LT tire, like their LTX M/S2, is at 44psi. In the case of this tire, it's 2,304LB @ 44psi. Not 35psi. Not 51psi.

Running the same tire at 35psi will have enough load capacity for the TRUCK MAX WEIGHT but the tires ARE NOT at the PSI needed for the TIRE MAX CAPACITY.

Tire max weight capacity is at the sidewall PSI and not the vehicle placard PSI. Period.
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Old 04-08-2019, 05:04 PM   #16
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so, if you increase PSI to 40, any safety concerns, do you get a better ride?
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Old 04-11-2019, 12:50 PM   #17
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so, if you increase PSI to 40, any safety concerns, do you get a better ride?
I tow my A-frame (about 3100 lbs loaded) with my 2008 Hyundai Entourage minivan (rebadged Kia Sedona) with over 200K miles on it. I use an E-2 600/6000 WDH to improve the towing experience and keep weight on the front end of the minivan.

The minivan has Michelin ZX P-metric tires. Door placard pressure is 35PSI. I consider this my minimum pressure (not towing I like 36-37PSI). When towing, I use 38-40 PSI, exact PSI depends where we are going elevation-wise and temperature-wise. If I'm headed Texas (6K ft lower) in the cooler months, I will use 39-40PSI. If I'm going in the summer or am going up in the Rockies, I like 37-38PSI.

Unloaded, I find 38+PSI to not cushion the minivan's ride as well. I set the tire pressures before every camping trip, and monthly if no camping trips are taken.

My tires wear evenly across the tread, which is the best indicator I'm getting it close to where it should be.

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