Tow Vehicle Tire Pressure

[nagel]

Do others increase / decrease the tire pressure in their tow vehicle when they are pulling the trailer? My truck specs say 35 psi for all 4 tires, but nothing about adjusting when towing.

I'm thinking I want to increase the tire pressure in the rear tires maybe to 40 psi when pulling the trailer. Thoughts? Is their a formula for figuring this out or should I leave it at 35? I'm thinking with the added tongue weight, it could cause the tires to "smash down" a little bit.

[OleManOleCan]

jadatis wrote:
35 psi is a tipical advice for standard load P-tires. It is the reference- pressure, wich is the pressure for wich the maximum load is calculated for reference-speed of 160kmph/99mph. Carmakers advice it nowadays often and dont calculate it anymore, I think for reasons of responcibility.

I once got hold of the European formula to calculate pressure, and went running with it, and now call myself pigheaded Dutch tirepressure specialist. Moast american towing vehicles have large tires with a maximum load that can carry almost the whole gross axle weight rating, so if calxulated , pressure for the P-tire would give about 26 psi. And after the Ford Firestone affaire, carmakers have become scared to advice this.

But this means that you dont need to highen up this 35 psi, it already has such reserve, that you can drive a bit overloaded and faster then 99mph.

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PROBLEM...
Underinflated tires lack sidewall strength.
TV tires that are underinflated allow the trailer to kind of wallor in curves.

ALSO...
Most hitches measure height by near full inflation.
Partial inflation can lower the hitch height, and change the
way your TV responds.
A hitch that's too low plus having a loaded truck bed is likely to sway or bounce.

I don't inflate my E-Rated tires to 85 PSI, ( I could ) but I do tow at about
65 PSI. I am guilty of running at 50 PSI when I'm not towing.
I figure I should not tempt fate, by inflating my tires at a low PSI.
A low PSI exposes more of your sidewall to road hazards.

Count me as an old guy who believes in PSI to help control your
truck and your camper.

[rbpru]

I have P rated half ton tires. The truck sticker says 34#. That give a decent ride around town.

When I tow I run 38# front and 40# rear. Works just fine.

The max cold pressure listed on the tire is 44#.

[trailer_newbe]

“”You, DON'T account for heat. The engineers have already done that. You always set them cold. If they are at correct pressure, the heat buildup is normal. Now, if one gets low that will create excess heat that can raise the pressure to the point of a blowout.

Mark””

I do not agree. The manufacturer list the MAX pressure on their side wall. Granted they usually say cold, but anyone who thinks they engineered all road temperature conditions, I have a bridge across the Grand Canyon I’ll sell you. Set to 80 PSI then drive through Yuma on a 120 degree day, bad idea. I’ve aired to 80 PSI then hit the road and observed 86 PSI, which I’m good with, but where I live the temperature (and more importantly) the asphalt gets so hot it starts to melt. You can’t just air to max (cold) and take off, because you need to compensate for the time of year and where you are heading.

[jadatis]

35 psi is a tipical advice for standard load P-tires. It is the reference- pressure, wich is the pressure for wich the maximum load is calculated for reference-speed of 160kmph/99mph. Carmakers advice it nowadays often and dont calculate it anymore, I think for reasons of responcibility.

I once got hold of the European formula to calculate pressure, and went running with it, and now call myself pigheaded Dutch tirepressure specialist. Moast american towing vehicles have large tires with a maximum load that can carry almost the whole gross axle weight rating, so if calxulated , pressure for the P-tire would give about 26 psi. And after the Ford Firestone affaire, carmakers have become scared to advice this.

But this means that you dont need to highen up this 35 psi, it already has such reserve, that you can drive a bit overloaded and faster then 99mph.

[AutomationIsCom]

All my tires are at max pressure per the sidewall information (about 60ish PSI) and I have had no issues at all at highway speeds. I also leave my truck tires at full PSI while driving every day and have not noticed any degraded experiences; still rides smooth and I have not noticed any excessive tread wear. I would consider letting air out if I was to go out on the beach though...... I've put about 800 miles on the trailer like this ( much more on the actual truck)

[GrandpaKip]

The max pressure on my truck tires is 50. Door calls for 34. When towing, I put 40 front, 45 rear.
They are Pmetric tires. I’m gonna keep them til they wear out.
This has worked well for the 9 months I’ve had this truck.

[allen8106]

nagel wrote:
Do others increase / decrease the tire pressure in their tow vehicle when they are pulling the trailer? My truck specs say 35 psi for all 4 tires, but nothing about adjusting when towing.

I'm thinking I want to increase the tire pressure in the rear tires maybe to 40 psi when pulling the trailer. Thoughts? Is their a formula for figuring this out or should I leave it at 35? I'm thinking with the added tongue weight, it could cause the tires to "smash down" a little bit.

You should run the tires at max listed pressure on the side wall, not over.

[myredracer]

nagel wrote:
Do others increase / decrease the tire pressure in their tow vehicle when they are pulling the trailer? My truck specs say 35 psi for all 4 tires, but nothing about adjusting when towing.

What are you towing? Something short & light or long & heavy? Must have a 1/2 ton? P rated tires aren't very good compared to E rated, esp. as you get into longer and heavier trailers. For towing you want stiffer, not Cadillac soft. 35-40 psi is Cadillac soft and will result in more sway/poorer handling.

Recently got a '12 GMC Sierra 2500. Sticker says pressure should be 80 psi on the rears and 65 front. I'm using 75 psi on the front.
We put a set of LRE Goodyear Wranglers on it which have stiff sidewalls with a kevlar belt. We tow a 29' 7K lb TT. The truck tows the TT as if it was on rails. Zero sway. I never thought towing could be so good!

Had an F250 for 7 years, towing the same TT. It had LRE Michelins on it and ran 80 psi rear & 75 front. Sidewalls are a lot more flexible compared to the Wranglers. I thought that towed pretty good, but wow, the Sierra tows so much better. Difference has to be in the tires and maybe the heavy duty trailer package on the Sierra.

When I first got our F250, I experimented with different pressures on the front & rear tires and settled on the 80 rear & 75 front for best handling & sway control. Can't recall what Ford said the psi should be but was a fair bit less than this. Some people are shocked at running such high pressures but only downside is maybe a harsher ride which doesn't bother me in the slightest. I reduce the pressure over the winter months.

FWIW, tire pressure in a TV is just one of a number of factors to consider when looking at reducing sway and improving handling, and they all work together as a "package".

[TurnThePage]

Too bad the original poster didn't specify more info about their tow vehicle. It certainly sounds like a 150/1500 series. Unlike 250/2500 and above, half ton trucks are most often tuned for comfort, not work. 35 PSI is a great pressure for daily driving, not for towing or hauling. I increase my P rated tire pressure to the sidewall max when towing, which greatly increases stability, and probably improves long term durability, through less heat build up too.

[Tvov]

You bet I lower the rear tire pressure when I am not towing / hauling... door pillar says 75psi - for maximum load/towing. When the truck is empty that pressure gives quite a rough ride.

I don't change the air pressure daily. If I am going to be doing a lot of towing, I keep them aired up. If I will be empty for awhile, I air them down a bit - usually to 65psi.

A lot of different information out in the internet, but I check tire pressures in the morning, when the tires are "cold". While traveling I keep my eye on them, and check them if something looks off - but I don't air up or down if all the tires are roughly equivalent pressure.

[Grit_dog]

SidecarFlip wrote:
I always run the recmmended pressures listed on my door pillar, loaded or empty, in my case, 65 psi in the front, 80 in the back. I never exceed those presssure ratings. The engineers who designed and the people who built my pickup know way more about what is correct than I do.

This actually makes no sense. The engineers that designed your tires also rate their load carrying capability vs pressure from about 35 psi up to the max. Not going to hurt anything running considerably more pressure than needed, except maybe your teeth and kidneys, lol.

[Grit_dog]

To the OP, yes you can and likely want to air up, some, when loaded or towing and air down for empty driving.
No, you don't have to account for temperature....or altitude, in general.
You have no need for 80psi on a 1/2 ton, unless you overload it by about 2000lbs. However load range E tires are a safe, versatile long lasting choice for tires on a 1/2 ton.
If your truck shakes with high pressure and not with low pressure, it most likely ain't the tires, it's the hard tires exaggerating another issue. (Bad shocks, bad ball joints, etc)

[Rustycamperpant]

I always run more pressure when towing my TT based on the recommended tire pressure chart that was shared on this site at one time.

[3inCoquitlam]

One of the first things I did was change out my factory P rated tires to LT (BFG KO2s). I run them at 65 when towing, back down to 35 empty.

[time2roll]

Door on mine says 36. I run 40F 45R towing or not. Only time I might air down would be if the off-road conditions dictate.