Tire pressure at 45 pounds

[TobyU]

The Wrangler DURA TRAC quoted is an E rated tire.
(LT in the model name)

LT275/65R18
123/120Q E BSW 32.1" 11" 7.5-9" 8" 18/32" E - 10 ply 3415 lbs 80 psi 99 mph 50 lbs Black 648

I'm not a tire expert but I did my homework for my 2 sets of E rated Light Truck tires. The 35 psi recommendation is for Passenger tires. LT tires "need / can use" higher pressure. There are tables to guide you in choosing what pressure to use, or you can do the chalk test, or various other methods. You don't want to go up to 80 psi unless carrying a heavy load of weight in the vehicle. I think that's most of the idea with LT tires, you can carry a much heavier weight -- the tire can handle that - but you need to crank the psi up to compensate for the weight -- the tire can handle that. Under normal weight you still want higher than 35 psi. I run about 46 psi in my Falken Wildpeak and Kumho Road Venture LT tires. That results in an appropriate tire shape and "footprint" on the road with good tire wear and gas mileage.

Do I have this right? I'm not always right, I know that and I'm always trying to learn.

MrLoki … if its an E rated LT tire do you still think 35 psi is correct?

Pretty much all you said is correct

The Wrangler DURA TRAC quoted is an E rated tire.
(LT in the model name)

LT275/65R18
123/120Q E BSW 32.1" 11" 7.5-9" 8" 18/32" E - 10 ply 3415 lbs 80 psi 99 mph 50 lbs Black 648

I'm not a tire expert but I did my homework for my 2 sets of E rated Light Truck tires. The 35 psi recommendation is for Passenger tires. LT tires "need / can use" higher pressure. There are tables to guide you in choosing what pressure to use, or you can do the chalk test, or various other methods. You don't want to go up to 80 psi unless carrying a heavy load of weight in the vehicle. I think that's most of the idea with LT tires, you can carry a much heavier weight -- the tire can handle that - but you need to crank the psi up to compensate for the weight -- the tire can handle that. Under normal weight you still want higher than 35 psi. I run about 46 psi in my Falken Wildpeak and Kumho Road Venture LT tires. That results in an appropriate tire shape and "footprint" on the road with good tire wear and gas mileage.

Do I have this right? I'm not always right, I know that and I'm always trying to learn.

MrLoki … if its an E rated LT tire do you still think 35 psi is correct?

I think you covered about everything. An E Rated Tire can be aired up all the way to 80 psi if you need to or wish to Halt its maximum load but it should never be aired above 80 when cold.
No tire should ever be inflated over the maximum cold inflation printed on the sidewall.
Most vehicles with load range D or E tires do not need to be at the maximum inflation pressure. Most will ride firmer or uncomfortable at these higher pressures. However, I have seen some vehicles that actually ride smoother at at when they do at 62.
There also is consideration like you mentioned about even tire wear. I am more concerned about even tire wear than I am about ride comfort.
Paying close attention to your tires or the chalk method is the best method to determine what the best pressure is for even wear.

Also as you mentioned a load range E Tire should not be at 32 lb or 35 lb because the manufacturer printed that pressure on the door placard. Any number given by the manufacturer and printed on any official literature from them will also state the exact tire size and load range the vehicle was shipped with and that number only applies to that exact tire specification.

Even if a vehicle has a standard load Tire which most Passenger cars do oh, most of those tires either have a maximum flexion pressure of 35 PSI or 44 psi. The manufacturer usually has a low recommended inflation than that and it's typically based on comfort. The tires cannot support their full maximum load printed on the sidewall at those pressures. Most people will never load their vehicle even close to those pressures so it's a moot point.

When you switch from a standard load to D or E load range Rated Tire you should always increase the pressure higher than what the manufacturer recommended for standard load tires.
These tires are made differently and often even look quite low with only 35 PSI.
Most people don't need to be at the maximum but people be much better serviced to start out with at least around 50 in a load range E Tire even on a light vehicle carrying no heavy loads and adjust them there. The lowest I have ever run in a load range E has been 60. I typically like to run right around 72 unless it's on a vehicle that typically haul a lot of weight and then I go up to the 80.

Even on standard load tires I go much closer to the maximum inflation printed on the side wall and consider that number much more important than whatever the manufacturer stated to fill them to.
Just because Ford says to fill your tire to 32 or 35 PSI does not mean it is the best pressure or even the safest pressure. It might be printed in the book or printed on the placard but that does not mean it is correct.

 

[LokiWolf]

Pretty much all you said is correct


I think you covered about everything. An E Rated Tire can be aired up all the way to 80 psi if you need to or wish to Halt its maximum load but it should never be aired above 80 when cold.
No tire should ever be inflated over the maximum cold inflation printed on the sidewall.
Most vehicles with load range D or E tires do not need to be at the maximum inflation pressure. Most will ride firmer or uncomfortable at these higher pressures. However, I have seen some vehicles that actually ride smoother at at when they do at 62.
There also is consideration like you mentioned about even tire wear. I am more concerned about even tire wear than I am about ride comfort.
Paying close attention to your tires or the chalk method is the best method to determine what the best pressure is for even wear.

Also as you mentioned a load range E Tire should not be at 32 lb or 35 lb because the manufacturer printed that pressure on the door placard. Any number given by the manufacturer and printed on any official literature from them will also state the exact tire size and load range the vehicle was shipped with and that number only applies to that exact tire specification.

Even if a vehicle has a standard load Tire which most Passenger cars do oh, most of those tires either have a maximum flexion pressure of 35 PSI or 44 psi. The manufacturer usually has a low recommended inflation than that and it's typically based on comfort. The tires cannot support their full maximum load printed on the sidewall at those pressures. Most people will never load their vehicle even close to those pressures so it's a moot point.

When you switch from a standard load to D or E load range Rated Tire you should always increase the pressure higher than what the manufacturer recommended for standard load tires.
These tires are made differently and often even look quite low with only 35 PSI.
Most people don't need to be at the maximum but people be much better serviced to start out with at least around 50 in a load range E Tire even on a light vehicle carrying no heavy loads and adjust them there. The lowest I have ever run in a load range E has been 60. I typically like to run right around 72 unless it's on a vehicle that typically haul a lot of weight and then I go up to the 80.

Even on standard load tires I go much closer to the maximum inflation printed on the side wall and consider that number much more important than whatever the manufacturer stated to fill them to.
Just because Ford says to fill your tire to 32 or 35 PSI does not mean it is the best pressure or even the safest pressure. It might be printed in the book or printed on the placard but that does not mean it is correct.

Mostly correct.

I run our LT E Load range tires on our 17 EL Limited at 42 in the Rear(Less weight than the front under normal conditions), and at 46 in the front. Currently it passes all of my chalk tests, pretty well. If we are traveling and carrying more people/stuff, I increase the rear to 48/50.

LT(E Range) will NEVER EVER need to be even close to 80 on an Expedition. The tires capacity WAY exceeds the vehicles capacity. Running anywhere above 60 in an E Range tire especially unloaded is just plain dangerous. Your contact patch is less, and the tires ability to conform to the surface and stop is greatly decreased. Grip is worse in all directions.

Remember for control, slightly low is ALWAYS better than high. That has been proven by MANY tests.

If you are running factory size passenger tires, run the recommended pressure and you will be fine, unless running a heavy load and I would increase the rears by 5 or 6 PSI to allow the tire to be closer to it maximum weight capacity. Still the tires that came with ours, the tire total on the rear axle still exceeded what the rear should have on it. The added pressure will help keep the side wall flex down, and equalize the contact patch again.

If take anything away from my words, please take this:

Running too high a pressure is just as bad as running too low. I would argue it is worse. A little low is always better than high when stopping distance and grip is taken in to play.

If you are going to run non-stock tires, do the work and figure out the best pressure for your vehicle and how you load it.


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[LokiWolf]

MrLoki … if its an E rated LT tire do you still think 35 psi is correct?

No. Running a higher pressure and doing the work to make sure it is correct is important.

The chalk test, and the wet tire test are always good.



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[Deadman]

yeah. a lot of folks say that. I've run multiple sets of e rated and passenger tires on multiple expys and I don't experience much difference in ride - if any (sound or comfort). but, i'm kind of dense and might not be able to differentiate. Possibly a little louder, a soothing sound!

I run e rated light truck tires for 2 reasons
1) a national park ranger advised me to do that for driving rough rock filled roads in the back country forest service lands. sidewall is tougher and less likely to cut
2) LT tires (at least the ones I buy) have deeper tread depth than passenger tires. I use snow rated tires and I want the deepest tread depth I can get for snow condition in the mountains and ski resort travel.

The Falken Wildpeak LT rated tires have 18/32" tread depth which is 3/32" deeper than the passenger version. That is the deepest tread depth I can find for a tire that performs well under all the driving conditions I plan for. I even retire those tires for winter use and buy new ones when the tread wears down (12/32"), using the worn down tires in the summer until spent (5/32").

Overkill I guess, but I like overkill!!

Again, after doing my homework, I determined that I need to inflate those LT tires higher than the recommended 35 psi for passenger tires

It makes total sense if you are wanting the added strength! The main place you notice the difference is that the E rated tires are usually very stiff and ride rougher. They are far stronger, so you are better safe than sorry with your needs!

Mine doesn't go off road enough to matter, so Its a different need!

 

[Deadman]

From a pinch standpoint, higher pressure is always better than lower. Low pressure offers the opportunity to pinch sidewalls especially when loaded heavier.

 

[LokiWolf]

From a pinch standpoint, higher pressure is always better than lower. Low pressure offers the opportunity to pinch sidewalls especially when loaded heavier.

If you are pinching a sidewall, you are running REAL low on pressure, overloaded, or doing things while loaded you shouldn’t.


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[TobyU]

From a tire safety standpoint a little bit too high is safer than a little bit too low. You might have less traction and you can even slide in to someone or having Kris stopping distance but to love you can overheat the tire in and have a catastrophic.
The industry professionals will tell you that slightly over is safer than slightly under but that does not mean exceeding the maximum flation on the sidewall.

I do agree that no one with the factory Expedition will ever need load range e tires at 80 psi. I personally don't feel anyone with an expedition will ever need load range e tires at all. Excursions only came with these from the factory and that was kind of Overkill. I wasn't speaking about these vehicles or vehicles in this form specifically oh, but rather vehicles and tires in general. Most people who have load range e tires have it on a larger or commercial vehicle. That is my case and my experience with load range e. All of the buses you see that the nursing homes and the churches use cam with 225 75 16 load range e tires. You do not inflate those tires ever to 45 or 50 lb. These vehicles do hold excessive amounts of weight with passengers so there is never a time one of those tires ever be inflated below 70.

 

[LokiWolf]

From a tire safety standpoint a little bit too high is safer than a little bit too low. You might have less traction and you can even slide in to someone or having Kris stopping distance but to love you can overheat the tire in and have a catastrophic.
The industry professionals will tell you that slightly over is safer than slightly under but that does not mean exceeding the maximum flation on the sidewall.

I do agree that no one with the factory Expedition will ever need load range e tires at 80 psi. I personally don't feel anyone with an expedition will ever need load range e tires at all. Excursions only came with these from the factory and that was kind of Overkill. I wasn't speaking about these vehicles or vehicles in this form specifically oh, but rather vehicles and tires in general. Most people who have load range e tires have it on a larger or commercial vehicle. That is my case and my experience with load range e. All of the buses you see that the nursing homes and the churches use cam with 225 75 16 load range e tires. You do not inflate those tires ever to 45 or 50 lb. These vehicles do hold excessive amounts of weight with passengers so there is never a time one of those tires ever be inflated below 70.

Agreed, but we aren’t talking a BUS. We are talking a family SUV with a 9K towing capacity.

LT tires feel much better on the Expy than my passenger tires did, by far. The stiffer sidewall helps with that a lot. Wife says the ride is much better...so win/win.

Heat build up to the point of failure is ONLY an issue if you are running WAY too low for the weight you are carrying and running A LOT of miles at high speed. Most modern tires can take an extreme beating before they fail.

Again, slightly low is better than slightly high. Better control because of give and contact patch. The heat in a slightly low situation will not be enough for failure, period. When I say slightly, I mean 1-2PSI, not 10.

Also, like I stated above, all of this can be solved by some testing at loaded weight using the chalk and wet tire test, and monitoring wear.



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[Plati]

I was at a remote campground in August, guy with fancy dancy Sportsmobile was camping there. Had to drive 10 miles on a ridiculously rough road to get there. He had a $500 tire inflator. He was horribly conflicted (worse than James Comey) because he let air out of tires to make ride in more cushy … but the rocks he was running over made him nervous about breaking a bead and losing air. Couldn't make up his mind to have cushy ride or maintain air in his tires. It was kinda funny.

 

[TobyU]

Agreed, but we aren’t talking a BUS. We are talking a family SUV with a 9K towing capacity.

LT tires feel much better on the Expy than my passenger tires did, by far. The stiffer sidewall helps with that a lot. Wife says the ride is much better...so win/win.

Heat build up to the point of failure is ONLY an issue if you are running WAY too low for the weight you are carrying and running A LOT of miles at high speed. Most modern tires can take an extreme beating before they fail.

Again, slightly low is better than slightly high. Better control because of give and contact patch. The heat in a slightly low situation will not be enough for failure, period. When I say slightly, I mean 1-2PSI, not 10.

Also, like I stated above, all of this can be solved by some testing at loaded weight using the chalk and wet tire test, and monitoring wear.



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The problem with that is the word slightly. You did clarify that you meant 1 to 2 lb anything less than 5 you are correct. It is quite fine for a tire to be 3 to 5 lb slow and better than being three to five times high for traction but the problem is when people hear something like that slightly to them becomes 10 or 15. As you said 10 pounds or more low is much more dangerous than 10 lb tire UNLESS it is 10 pounds over the maximum inflation pressure on the sidewall.

We are talking about tires and recommended and rated tire pressures and load capacities. It doesn't matter what vehicles were talking about. When I say the rule is you never inflate a tire past the maximum inflated pressure on the sidewall that applies to all tires regardless of what type of vehicle they're going on.
The original poster was discussing an expedition but then someone else started talking about load range e tires which do not come on Expeditions, and mention when they were hauling a load and their trailer. All of this changes the same situation. Towing with a truck with a large trailer with a heavy load is just as different an application as a tire being on a minibus.
Most of what I'm talking about are on stretch limousines as opposed to buses anyways. I just use the bus for reference because most people know what the E-Series van bus chassis for churches look like.

I've run lots of both types and even 40 foot long MCI buses with 22.5 in commercial bus tires.

The problem with going by Vehicle Manufacturer recommendations can be multi-faced. Someone who has an expedition that came with standard load tires on it that says to inflate to 32 pounds or 35 pounds might decide to take some new take off tires off of an F 250 or 350 Ford Excursion. Let's assume the wheels fit for they are changing the tires on the rims. If they have a load range D or E Tire and they put that on their expedition they should not be airing them to 32 psi.
If they checked them with the chalk method like you do they would see they are underinflated at those pressures but most people never do that. They like it easy. They just want someone to tell them or read the manual and believe they're doing the right thing but in reality they would not be.

Let me just reiterate that the simplest method is you never inflate a tire beyond the maximum pressure printed on the sidewall and you can't always or even often go by what the Vehicle Manufacturer recommends unless you have the exact same type, size, and load range of tire that it came from the factory with.