Increase tire pressure when towing?

[CindyC-IL]

Mechanic at my local garage told me I should increase tire pressure on truck when towing. Recommended driving is 35 psi with max being 65 psi. Not heard this before. Wondering if this is true or depends on what towing, weights etc.

Thanks

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[FaaWrenchBndr]

What exact tires do you have?
That really makes no sense.

Factory installed tires pretty much max at 44 psi, if I remember correctly. If you have a higher loader range tire than the factory said, you shouldn’t be driving them around with 35.

But yes, it is fairly common to add air to your tires when towing. Many people will run their tires toward the higher end of the recommended pressure to decrease rolling resistance and increase fuel mileage but, it’s sacrifices right quality.

 

[Davexxxx]

What exact tires do you have?
That really makes no sense.

Factory installed tires pretty much max at 44 psi, if I remember correctly. If you have a higher loader range tire than the factory said, you shouldn’t be driving them around with 35.

But yes, it is fairly common to add air to your tires when towing. Many people will run their tires toward the higher end of the recommended pressure to decrease rolling resistance and increase fuel mileage but, it’s sacrifices right quality.

OEM Goodyear Wrangler Territory ATs 275 65 18 M+S Standard Load

Door sticker = 35psi.

Tire max = 51psi

I run them at 40 for daily and 50, while towing.

 

[amschind]

The trailer will increase the pressure as well by mashing on the tires, so i normally check and fill the tires AFTER the loaded trailer is on them.

 

[Davexxxx]

The trailer will increase the pressure as well by mashing on the tires, so i normally check and fill the tires AFTER the loaded trailer is on them.

Thats not how it works.

There is a fixed amount of air, in a fixed amount of space.

The tire changes shape but not volume. In fact, they do this constantly, any time the vehicle is moving.

 

[Buyer2021]

FYI / FWIW a table I made when I was considering tire pressure 'adjustment' when towing the 5th-wheel described in my signature block. The tire loads are based on CAT Scale axle weights divided by 2, this is all with the rig 'loaded for travel'

As you can see in my case the tire loads really don't change much or approach any rated limits even with the trailer hitched (still ~close to middle of the tire's rated load). I experimented with bumping rear tire pressure +10psi, got no perceptible benefit, just a tad more harsh ride, I've stuck with the placard 35psi cold for thousands of towing miles since. No measurable oddities observed in terms of tire wear and the rig handles great.

Your situation may differ of course depending on your 'loaded for travel' loads**. IMO nothing beats getting actual weights on a CAT Scale to help evaluate this sort of thing.

Have Fun!

** Back when I was towing a 16' ag trailer with my '05 F150 and had both truck-bed and trailer fully loaded with hay bales, I would definitely increase my rear tire pressure.

 

[Davexxxx]

FYI / FWIW a table I made when I was considering tire pressure 'adjustment' when towing the 5th-wheel described in my signature block. The tire loads are based on CAT Scale axle weights divided by 2, this is all with the rig 'loaded for travel'

As you can see in my case the tire loads really don't change much or approach any rated limits even with the trailer hitched (still ~close to middle of the tire's rated load). I experimented with bumping rear tire pressure +10psi, got no perceptible benefit, just a tad more harsh ride, I've stuck with the placard 35psi cold for thousands of towing miles since. No measurable oddities observed in terms of tire wear.

Your situation may differ of course depending on your 'loaded for travel' loads**. IMO nothing beats getting actual weights on a CAT Scale to help evaluate this sort of thing.

Have Fun!

** Back when I was towing a 16' ag trailer with my '05 F150 and had both truck-bed and trailer fully loaded with hay bales, I would definitely increase my rear tire pressure.

While I have used CAT scales several times with my trailer, I set tire pressure more by feel.

35 IMO, is too soft a ride, especially in cornering. 40 tightens that up without being too harsh. Admittedly, I did pull the 50, more or less out of my ... hat

 

[FaaWrenchBndr]

OEM Goodyear Wrangler Territory ATs 275 65 18 M+S Standard Load

Door sticker = 35psi.

Tire max = 51psi

I run them at 40 for daily and 50, while towing.

And that’s something like what I was expecting.
Where did this shop get this 65 psi number from?
They pull it from thin air or their arse?

 

[JohnTrigger]

And that’s something like what I was expecting.
Where did this shop get this 65 psi number from?
They pull it from thin air or their arse?

Well, let’s see, if they took air FROM their arse at 98.6 deg and filled it to 65 PSI, when it cooled down ~40 deg to standard atmosphere temp of 59 deg it would read about 61 psi. Now if they used thin air too…oh jeez I’m not sure what would happen. lol.

 

[UGADawg96]

I run LT tires at 40-45 when not towing and 45-55 when towing our 6500lb TT.

 

[FaaWrenchBndr]

Well, let’s see, if they took air FROM their arse at 98.6 deg and filled it to 65 PSI, when it cooled down ~40 deg to standard atmosphere temp of 59 deg it would read about 61 psi. Now if they used thin air too…oh jeez I’m not sure what would happen. lol.

You’re a genius…….a comedian as well!

That was a GOOD one!

 

[Tone]

Had the same question and called Michelin's help line. The recommendation was 35 all around even when towing. Have no issues. When towing on a hot summer day they'll rise to about 38. Mileage remains fantastic.

 

[Ricksc]

I run 50 in rear 45 front when towing. More air will keep sidewalls firmer. Less chance of sidewall failure. You are adding weight to tires there for need more air.

 

[Chris GTO TT]

FYI / FWIW a table I made when I was considering tire pressure 'adjustment' when towing the 5th-wheel described in my signature block. The tire loads are based on CAT Scale axle weights divided by 2, this is all with the rig 'loaded for travel'

As you can see in my case the tire loads really don't change much or approach any rated limits even with the trailer hitched (still ~close to middle of the tire's rated load). I experimented with bumping rear tire pressure +10psi, got no perceptible benefit, just a tad more harsh ride, I've stuck with the placard 35psi cold for thousands of towing miles since. No measurable oddities observed in terms of tire wear and the rig handles great.

Your situation may differ of course depending on your 'loaded for travel' loads**. IMO nothing beats getting actual weights on a CAT Scale to help evaluate this sort of thing.

Have Fun!

** Back when I was towing a 16' ag trailer with my '05 F150 and had both truck-bed and trailer fully loaded with hay bales, I would definitely increase my rear tire pressure.

Word of caution here the factory P-series tires (and all SL P-series tires) are rated to carry their maximum load at 35psi. Adding more pressure doesn't increase load carrying capacity as it would on an LT Tire.

https://www.tirerack.com/upgrade-garage/what-is-maximum-load-for-a-tire

 

[honda250xtitan]

The trailer will increase the pressure as well by mashing on the tires, so i normally check and fill the tires AFTER the loaded trailer is on them.

I like your science book. Please send to me.

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