Tow vehicle tire pressure

[nvestysly]

Originally Posted by SpletKay06

Youll need to weight your axles and then Compare your tire weight to the load inflation chart of your time manufacturer.

This thread contains lots of anecdotal information about what works and what doesn't but SpletKay06 is on the right track. If you haven't taken time to obtain axle weights (and individual tire weights) all this discussion may lead you down the wrong path.

Look below for example of a tire inflation chart posted by Michelin. Do some digging and find a chart for your brand, wheel diameter, and model of tire. Then check the weight on your axle - it's easy to do at a truck stop. Compare your tire weight (axle weight divided by two will be pretty close) to the chart and air up your tires to the correct pressure.

[nvestysly]

Originally Posted by LyleRussell

You all realize that tires heat up as soon as they start rolling. My rears typically gain 5 psi after rolling for 10 minutes. More on hot days. Going above the sidewall specified max seems to be uncool.

Tell us more about what you're saying. I may be misunderstanding what you're getting at.

Do you mean we should try to take into account how much the tire/air will increase in temperature and then back off of the amount of air we put into the tire in order to compensate for how much it's going to rise in temperature? If so, I don't think that's what tire manufacturers are saying.

Tire charts almost always indicate to check pressure when tires are cold. You can argue that in northern climates in the winter the cold temperature is quite a bit different than a cold tire in the summer months in a warm climate. We could probably discuss that all day and then some. Regardless, if you check the tires when cold - regardless of what "cold" temperature actually is - then I think you are following the manufacturers guidelines.

Filling a cold tire to maximum pressure, assuming it needs that to support the load, then yes - the pressure will be above the sidewall rating when hot. Don't check tire pressure when the tires are hot.

[Bob662]

It seems to me that there is no reason to go higher that the DOT sticker for the front tires. Many truck manufacturers now suggest restoring at least half the rise from TT tongue weight on the hitch. That being the case, the front wheels have less load on them with the WDH bars attached, than when the trailer isn't connected, so no reason to go up on front wheel tire pressure?

The rear wheels are different. they are carrying more load than if unhitched, so I get why more pressure is appropriate.

[JCWDCW]

You want the maximum load carrying capacity of the rear tires. You are probably fully loaded with trailer tongue weight and rear compartment load in the TV. Pump them up to max rating on the tire sidewall. For the front tires it is a matter of trial and error. You want enough pressure to carry the extra load transferred by the WD set-up but only enough to give a good foot print on the front for good steering, braking and no squirm in the nose dive in a hard stop. On my Dakota I run full 44 psig rear and 35 psig front. I get good even wear and the tries run cool. Once in Tx we had the oil changed at a Pep Boys and they dropped the rear pressure (unknown to us) to standard comfort level. We discovered very hot tires two days later, which also explained the sloppy handling. We were fully loaded in the box, and not pulling a trailer. Always inform your garage what pressures you want in your tires.
JCW

[ROBERTSUNRUS]

Originally Posted by JCWDCW

Always inform your garage what pressures you want in your tires.
JCW

Hi, If about to travel with my trailer, or while towing on the road, I always tell the shop what tire pressure that I want.

[AtomicNo13]

Wasnt forum member "capriracer" a tire engineer for a big mfgr?

I wonder what he would offer...

[CapriRacer]

Originally Posted by AtomicNo13

Wasnt forum member "capriracer" a tire engineer for a big mfgr?

I wonder what he would offer...

Yes, I was. And I used to answer questions on this subject.

First, there is a vehicle tire placard on every vehicle sold in the US - and if I understand this correctly, the rest of the world as well. That is the pressure specified by the vehicle manufacturer for the tire size indicated - and because of that, MUST be able to handle the maximum specified payload plus the vehicle weight - that is, the fully loaded condition.

It is my understanding that if the vehicle manufacturer wishes, they can specify pressures for other conditions (such as fully empty) either on another sticker, or in the owners manual, (or not at all!)

Please note that because tires are standardized, it doesn't matter where a tire is manufactured or by whom, that pressure will apply for all tires of that particular tire size. It does NOT apply to tires of a different size.

Please also note, there is a difference between P type tires and LT type tires - and I include those letters when I say *size*.

Second, every tire sold in the US must be marked with a maximum load and a maximum inflation pressure. This comes in 2 forms:

a) Max Load XXXX, Max pressure YY - note that no relationship is implied.

b) Max Load XXXX at YY pressure - note that the max pressure is NOT specified, but a relationship is.

My experience says that ALL LT tires are done per the second method - and what you should take away from that is that you can use more pressure than what is listed - BUT - I would warn folks to be careful when they do that they have a good grasp of the principles involved.

My experience also says that P type tires use the first methods a lot, but there are some tires listed the second way. My experience also says that some tire manufacturers (and some dealers) aren't very tidy about things and will list the maximum pressure using the *@* symbol - indicating a relationship, which in my view is not correct.

Perhaps, *misleading* is a better word! I hope dkottum won't think I am picking on him, but here is a quote that illustrates the problem:

Originally Posted by dkottum

Truck GVWR 6950
Both axle total 7800
Four 20" P-rated tires max total load 10400 at 44 psi ........

I'm sorry, but those tires at rated for max load at 35 psi, while 44 psi is the maximum.

Please note: I am not a fan of using the published load tables to set pressures. Not only do most people not understand how to do this correctly, a person can change the handling characteristics of the vehicle for the worse. If you've watch NASCAR races, you will hear comments about changing pressure to changes the handling of the car. The principal applies to trucks as well.

So I am a firm advocate of using the vehicle tire placard pressures unless you change tire size. If that is not enough to suit you, I'll suggest you get a bigger truck.

[Bgibbs]

My tv is an '06 2500HD Duramax and I always use pressures recommended on the door sticker. 55 F, 80 R. I use this when towing or not towing. I also know that tires are always ready to do what they are asked to do. Take a trip, tow a boat, Airstream, car trailer or haul a pallet of St. Augustine grass. In almost 200,000 mile, it has worked for me.

[m.hony]

My tires appear to wear evenly at 33 psi, but my tires get replaced due to age rather than miles.
I replaced tires at 35,000 miles in 2014 on a 2007.
The tires were 7 years old and had plants of tread left, but the cracking sidewalls scared me.
Now the truck has 53,000 miles- 18,000 miles on the second set of tires- wear is even.


Sent from my iPad using Airstream Forums

[phil1ben]

I have a 2007 F-150 Supercrew 4x4 and just today bought Defender LT tires LT275 65R-18 which is the OE size. Will probably buy a new Int'l Sig 25FB in the spring. However, the placard on the truck only provides inflation for P rated tires.

I went to the Michelin website and they have a chat function. I asked the "chatee" what pressure I should run without the trailer and what pressure with a 6500 pound trailer. She said she could not comment about inflation with the trailer.

She said their new recommendation for LT rated tires without a trailer for the size I have is 60lbs per tire front and rear.