Tire Pressure thoughts/recommendations

[Golds]

I would like to get some thoughts on whether my line of thinking on tire pressures for my truck is right.

I have a 2015 Ford F-150 with a GVWR of 7000lbs, Front Axle 3450lbs, Rear Axle 3800lbs. The truck has Goodyear Wrangler Fortitude HT 275/65R18 116T tires with a max load rating of 2756lbs at a max 51PSI. The recommended pressure is 35PSI front and back.

When the truck is loaded and the trailer is hooked up the front axle weighs 3100lbs and the back axle is 3198lbs for a total of 6280lbs.

I could not find a load/pressure chart for these tires but I found a generic chart. If I read it right these tires should handle 2115lbs at the recommended 35PSI. That would be 4230lbs per axle or 8460lbs for the truck.

If I am looking at this right then I should never have to run more than 35PSI in the tires even when I am towing the trailer.

I had been towing with the tires at 50PSI but the truck beats us up on bumpy roads so I would prefer to use the recommended 35PSI. Also, at 51PSI that gives 11,024lbs which is way over kill.

Is my line of thinking on tire pressure for towing right or am I completely off base? It seems to me that the recommended 35PSI would be more than enough for the weights I am dealing with.

[Murff]

It has been my experience that when towing, the tires should be inflated to their posted maximum.

Others may have other opinions.

Murff

[DEM]

I run with 35 psi on a 2014 F150 STX pulling a 2012 25RKS Jayflight.

[Jagiven]

Don't have a Ford, nor those tires. But I replaced my tires last year. Prior to the tire change, I ran at 35 psi, all the time, the combo handled really nicely. Changed tires, and I did not like how it handled. Change the tire pressure, in my case, increased them, until I found a good ride with the trailer. During the summer, I maintain the higher pressure, the ride is a bit more stiff. During the winter, I lower the pressure, to improve the ride.

[SkyBound]

I wouldn't run the base 35lbs while towing. I would suggest at least 40 if not 45. If 50 is too much then try lessening 5lbs at a time. I suspect you'll be happy with 40-45.

I run 50psi unloaded in my truck and 60 when towing - I upgraded to load range E LT tires. My truck originally came with P rated tires recommended at 35psi. That was a joke and those tires were removed and sold immediately.

My dad's truck (same as mine) came with load range C LT tires and his door sticker says to run them at 40psi.

[DocBrown]

My trailer is not as big or heavy as yours. However I run 45 in my rear tires and 35 in the front. I tried more on the front but I find the steering to be a bit squirrelly if it has much more than 35.

[Golds]

I have also been thinking of trying 40-45lbs in the rear and keeping the front at 35lbs. I know when I had the front at 50lbs the front tires seemed to bounce and want to skip across the payment whenever you hit a hole or ridge in the road. Have the backs at 50PSI would jar the entire truck when you hit a hole, very uncomfortable ride. I have also written Goodyear with all of my technical information to see what their professional recommendations are for these tires. I would think that running a little more air, especially in the rear tires, while towing would help the tires wear better and give less sidewall flex for better handling.

We shall see what Goodyear says.

Thanks for all of the responses.

[jal0710]

I have a GMC D/A combo and the suggested tire pressures are 60 in the front and 70 in the back. That's what I have done since buying the truck and, while the ride is a little rough around town and on bumpy roads, it's fine pulling the FW and rides almost as nicely as our car on the highway when empty. After all, it's an HD, not a Cadillac.

[Ottawasteve]

When towing I run my LTX MS2's on my F150 at 41 psi all the way around. 5 or 6 psi does not sound like a lot, but remember that it is about 17% of the recommended 35psi. I find that it does stiffen up the ride a little which is preferable for towing. I wish our TPMS measured temperature so I could see if there is any appreciable temp difference at different inflations.

[Jagiven]

Originally Posted by Golds

I have also been thinking of trying 40-45lbs in the rear and keeping the front at 35lbs..

That is were I started at, and after a few trips, my fronts ended up at 42 psi, and the rear at 45.

[Golds]

Here is what I have found out from doing research and a little information from Goodyear, OK, the Goodyear information was useless as well as their website, can't find any information on this tire and the load/inflation table. When the girl from Goodyear wrote me back she quoted values for a tire with a 114 load rating and these are 116. So basically useless.

From reading the great information from the Bridgestone and Toyo tire websites, they both have the same information, I found out that when you run a passenger tire on a light truck class of vehicle (which includes pickups, vans and minivans, and SUVs) it is the federal law that you have to reduce the load carrying capabilities of the tire by 1.1, in other words divide the max weight by 1.1. So my tires are rated at 2756lbs which means on a light truck their max is actually 2505lbs, nice to know.

I also found out that passenger tires reach a max weight at a pressure lower than max allowed pressure and by increasing the pressure you do not increase the weight capability of the tire. You only increase the speed capability and change the handling characteristics. These tires are rated at a max weight of 2756lbs (2505lbs if on a light truck) at 36PSI which means from 36PSI to their max pressure of 51PSI it is still 2756lbs (2505lbs). So by running a higher pressure you are not increasing the tires ability to handle more weight, you are only changing its handling characteristics. So in this case if you want a stiffer sidewall while towing to reduce flex and sway induced by the sidewall, run a higher pressure. If you don't like the trade off of a harsher ride, it is not necessary.

I wonder why Ford does not put this type of information in the owner's manual under the towing or tire section? It would be really nice to know.

So now we are all educated a little more when it comes to running passenger tires on a light truck (or at least I am) and using it for towing. Of course if you are running LT tires none of this applies because it is a completely different set of rules and load charts.

Oh, by the way, your ST trailer tires should always be ran at the max pressure no matter how much weight you have on them. This was the information I found on numerous different trailer tire sites that make trailer tires. As a matter of fact most of them void the warranty if you were not running at max pressure.

[Firefighter78]

For those who remember what happened when Ford thought they knew more about tires and pressure than the tire manufacturers with the Explorer. Unfortunately we lost inocent people due to those idiots. When I towed with my F150, I ran the tires at rated pressure on the sidewall and fronts at 35. Even on my current SRW F250, I run 70psi in the rear 65 in the front. Tires rated at 80 psi max but my Truck tows perfectly with 1,100 lbs of torque weight and bed packed at those pressures. Good luck and be safe!

[Country_Mouse]

Originally Posted by Ottawasteve

When towing I run my LTX MS2's on my F150 at 41 psi all the way around. 5 or 6 psi does not sound like a lot, but remember that it is about 17% of the recommended 35psi. I find that it does stiffen up the ride a little which is preferable for towing. I wish our TPMS measured temperature so I could see if there is any appreciable temp difference at different inflations.

How do you like these tires? Looking at the new Michelin Defender LTX MS tires for our 2004 Expedition. Load rating 113 which Expy is rated for. They are pricey at $204 each from Costco.

Currently have 285 50 R20's that previous owner put on. Stock was 265 70 17.

Trying to figure out if P rated is sufficient with a RAWR of 4128 or if we should get LT's.

[Golds]

Originally Posted by Country_Mouse

How do you like these tires? Looking at the new Michelin Defender LTX MS tires for our 2004 Expedition. Load rating 113 which Expy is rated for. They are pricey at $204 each from Costco.

Currently have 285 50 R20's that previous owner put on. Stock was 265 70 17.

Trying to figure out if P rated is sufficient with a RAWR of 4128 or if we should get LT's.

We have only put 3000 miles on the truck so far but the tires seem fine for what I have driven, no snow or heavy rain. The ride is good at the recommended 35PSI but is extremely rough at the max 51PSI, as would be expected. I really don't have anything to compare it to because I have never had any other tire on it.

I did have a truck in the early 90's that came with LT tires that made the ride very rough. When I replaced them I went with passenger tires and there was a great improvement, did not regret the decision. But the truck was not used for towing, just daily driving, so the change to passenger tires was a good idea.

[Ottawasteve]

Not sure about the Defender, but when I bough, the Michelin LTX MS2's were Costco's bestselling tire (in Canada and the US) and they had the weight ratings I was looking for. I run them all year round and they are vey quiet and have very good traction in the snow. They probably would not fare that well off road because the tread is not aggressive enough which is what gives it the quietness on the highway. They are definitely a huge improvement over the Wranglers that came with the truck and mileage rating on them was about 10,000 miles more than most comparable tires which is something to factor in. I air them up 5 to 6 pounds for towing which makes the ride a little harsher but makes the tow more stable. The Michelins are also praised on Tire Rack etc. As mentioned above, one of the only complaints is the price, but they are definitely worth the $10 per tire more than the Goodyear replacements were.

[Golds]

Originally Posted by Ottawasteve

Not sure about the Defender, but when I bough, the Michelin LTX MS2's were Costco's bestselling tire (in Canada and the US) and they had the weight ratings I was looking for. I run them all year round and they are vey quiet and have very good traction in the snow. They probably would not fare that well off road because the tread is not aggressive enough which is what gives it the quietness on the highway. They are definitely a huge improvement over the Wranglers that came with the truck and mileage rating on them was about 10,000 miles more than most comparable tires which is something to factor in. I air them up 5 to 6 pounds for towing which makes the ride a little harsher but makes the tow more stable. The Michelins are also praised on Tire Rack etc. As mentioned above, one of the only complaints is the price, but they are definitely worth the $10 per tire more than the Goodyear replacements were.

I am a big fan of Cooper Tires. I have never ran the truck tires but have ran them on my passenger cars for years and I love them. I am also upgrading my 65 GTO to 17" tires and I am considering Cooper for it as well. When my Goodyear's on the truck wear out I might try the Cooper truck tires and see how they do.

[Country_Mouse]

Originally Posted by Golds

I am a big fan of Cooper Tires. I have never ran the truck tires but have ran them on my passenger cars for years and I love them. I am also upgrading my 65 GTO to 17" tires and I am considering Cooper for it as well. When my Goodyear's on the truck wear out I might try the Cooper truck tires and see how they do.

We ended up going with a set of Cooper Discoverer's LSX Plus 275/55/R20 XL 117T for our Expedition.

Too early to tell how good they are but definitely a little louder than our Hankooks were.

[Golds]

Originally Posted by Country_Mouse

We ended up going with a set of Cooper Discoverer's LSX Plus 275/55/R20 XL 117T for our Expedition.

Too early to tell how good they are but definitely a little louder than our Hankooks were.

Don't like loud, that is not good. If you don't mind update me after you have put some miles on them and let me know what you think.

[Country_Mouse]

Originally Posted by Golds

Don't like loud, that is not good. If you don't mind update me after you have put some miles on them and let me know what you think.

I should clarify that I had summer only and 111 load rating tires before so not exactly apples to apples. Not sure how much difference one should expect moving to XL all season tires. It's really not too bad. Kids didn't notice. I knew going in that their noise ratings weren't as good as Michelin's from consumer Reports.

[Golds]

Originally Posted by Country_Mouse

I should clarify that I had summer only and 111 load rating tires before so not exactly apples to apples. Not sure how much difference one should expect moving to XL all season tires. It's really not too bad. Kids didn't notice. I knew going in that their noise ratings weren't as good as Michelin's from consumer Reports.

Yeah, that would be hard to compare since they are so different.