Looks like 30psi ought to be plenty good for towing

[chrispitude]

Well not really, but no wonder there is so much confusion on the topic!

I have a 2006 GMC Yukon Denali XL with the factory tow package. I'm getting things set up to tow a 2019 Jayco X23E, which is around 6000lbs ready to travel. I don't know the tongue weight yet, but I'm guessing it's around 750lbs.

The door sticker lists the cold pressure as 30psi, with no additional ratings for increased loading:



The manual doesn't say much about the label:



It mentions a bit about not underinflating or overinflating:



and most interestingly, states that "The recommended cold tire
inflation pressure, shown on the label, is the minimum
amount of air pressure needed to support your vehicle’s
maximum load carrying capacity":



So 30psi is the minimum, and apparently I'm free to go above that. But how far above?

I'm running Vogue Signature V SCT tires in a P275/55R20 fitment. They are XL load range P tires, and the sidewall max pressure is 50psi.

The Tire and Rim Association (TRA) inflation tables for this tire size gives ratings up to 35psi.

My thinking at the moment is:

• Since I'm aiming for the hitched-up front axle weight to be only 100lbs above the unhitched weight, I'll run 35psi cold in the front.
• Since the rest of the tongue weight will be on the rear axle, plus I'd like to minimize squirm near the pivot point, I'll run 40psi cold in the rear.

Does this seem like a reasonable starting point?

[chrispitude]

mkirsch wrote:
After all this discussion and tangential information, the simple answer is, you can go to maximum pressure as listed on the tire sidewall.

I would personally only do that if I felt some deficiency in the handling of the vehicle, or evidence of underinflation on the tires themselves.

I think my plan is to try 40psi, 45psi, and 50psi on the back axle and see if I feel any difference. I'll also use my FLIR infrared gun to check temps across the tread. And of course, I'll report back here with my findings - and with IR pictures!

[JIMNLIN]

I started a thread to get advice on how much higher to go than the sticker minimum. Are we agreeing?

no we don't agree.
You've gotten pages of advise on best psi to run those rear P tires at.

[mkirsch]

After all this discussion and tangential information, the simple answer is, you can go to maximum pressure as listed on the tire sidewall.

I would personally only do that if I felt some deficiency in the handling of the vehicle, or evidence of underinflation on the tires themselves.

Being a little overweight should not concern you, maybe a couple hundred pounds. Not a big deal, as long as you're under the tire weight ratings.

[chrispitude]

JIMNLIN wrote:
Tires on the back of a truck need proper air pressure to do two things.
1. ......carry the load without over heating at highway speeds.

2. and more air pressure to stop sway/handling issues....which means more psi to stiffen the sidewalls as a trailer can pushing the back of the tow vehicle around. P tires 44-51 psi is a very soft tire in the load carrying world of tires. I wouldn't run any P tire on the back of a truck carrying a load and pulling a trailer at anything less than max sidewall....especially those wide base /55-20" tires.

I've seen other 1/2 ton size vehicle owners go with those huge 20" E tires ....but come back in a few months and reported selling them and going with the std 17" OEM wheels and P265/70-17 tires.

I'm not sure I understand where you went with this. The P275/55R20 and P265/70R17 tire sizes differ in circumference by less than 1%. Tires can be characterized by (1) load rating and (2) sidewall flex; both sizes are rated for the load, and there is less sidewall flex in the P275/55R20 size. I started a thread to get advice on how much higher to go than the sticker minimum. Are we agreeing?

[JIMNLIN]

Tires on the back of a truck need proper air pressure to do two things.
1. ......carry the load without over heating at highway speeds.

2. and more air pressure to stop sway/handling issues....which means more psi to stiffen the sidewalls as a trailer can pushing the back of the tow vehicle around. P tires 44-51 psi is a very soft tire in the load carrying world of tires. I wouldn't run any P tire on the back of a truck carrying a load and pulling a trailer at anything less than max sidewall....especially those wide base /55-20" tires.

I've seen other 1/2 ton size vehicle owners go with those huge 20" E tires ....but come back in a few months and reported selling them and going with the std 17" OEM wheels and P265/70-17 tires.

[lawrosa]

chrispitude wrote:

DRTDEVL wrote:
You are overthinking this by a lot. You have another problem staring you in the face, yet you don't even realize it.

Your GVWR is 1313 lbs more than the curb weight of that Yukon XL. Your estimated tongue weight is 750 lbs, leaving you 563 lbs. If you put 30 gallons in the fuel tank, you are now down another 240 lbs, leaving only 323 lbs for all passengers and gear.

Yes, I don't like how close this is either.

It's two adults (400lbs), two kids (100lbs), two dogs (100lbs). We tow with the third-row bench removed, which is a heavy SOB, to reduce weight for this reason. So our 600lbs family minus the bench seat weight credit must be less than 563lbs. If that's true, it's just barely. We keep the trailer cargo as close as possible to the trailer axles, both to minimize angular momentum and the contribution to tongue weight.

I'm hoping my tongue weight is less than 750lbs, but only a trip to the scales will tell the full story.

When you go to the scales go by tour door tags axle weight.

Example. If scale weight has you at say 3800lbs rear subtract from your door tags 4000lb. That would leave you 200 lbs.

Dont worry so much about the GVW of the truck.

Use this calculator when you do the scales. makes it easy. you need 3 passes.


http://towingplanner.com/ActualWeights/TravelTrailerCatScales

[chrispitude]

1320Fastback wrote:
If your that close I think I'd change rims and tires to E rated.

Won't help with vehicle and suspension but might make a scary situation or blowout never happen.

I wanted to switch to load range LT-D tires, but all the LT tires in this size are super-knobby offroad tires. There wasn't a decent highway tire in the bunch.

So I went with the next load range down (P-XL), which is at least at the top of the P range. That led to me wanting to run a higher-than-sticker-minimum tire pressure, which resulted in this discussion thread. 🙂

[ppine]

I agree that your should read the tire sidewall.

[1320Fastback]

If your that close I think I'd change rims and tires to E rated.

Won't help with vehicle and suspension but might make a scary situation or blowout never happen.

[chrispitude]

DRTDEVL wrote:
You are overthinking this by a lot. You have another problem staring you in the face, yet you don't even realize it.

Your GVWR is 1313 lbs more than the curb weight of that Yukon XL. Your estimated tongue weight is 750 lbs, leaving you 563 lbs. If you put 30 gallons in the fuel tank, you are now down another 240 lbs, leaving only 323 lbs for all passengers and gear.

Yes, I don't like how close this is either.

It's two adults (400lbs), two kids (100lbs), two dogs (100lbs). We tow with the third-row bench removed, which is a heavy SOB, to reduce weight for this reason. So our 600lbs family minus the bench seat weight credit must be less than 563lbs. If that's true, it's just barely. We keep the trailer cargo as close as possible to the trailer axles, both to minimize angular momentum and the contribution to tongue weight.

I'm hoping my tongue weight is less than 750lbs, but only a trip to the scales will tell the full story.

[Grit_dog]

Not sure if the OPs orig post was serious or tongue in cheek, but either way, his rims will take 50psi no problem.

[DRTDEVL]

mike-s wrote:

DRTDEVL wrote:
Your GVWR is 1313 lbs more than the curb weight of that Yukon XL. Your estimated tongue weight is 750 lbs, leaving you 563 lbs. If you put 30 gallons in the fuel tank, you are now down another 240 lbs, leaving only 323 lbs for all passengers and gear.

Curb weight includes fuel and all other fluids. Dry weight doesn't.

OK, so add 240 lbs back, and you're at 203 lbs capacity remaining for the kids and all the cargo. Being that he bought a triple bunkhouse and has a Yukon XL, I would venture to guess there are more than 2 kids coming along. Three kids averaging 68 lbs would put him over GVWR, without adding a single bag of pretzels or a couple sodas. The issue didn't change a bit, that' not enough truck to legally and safely pull that trailer when it's outfitted for camping and there is anyone else on board with him. He either needs a bigger ride, or the family needs to follow him in another vehicle.

[mike-s]

DRTDEVL wrote:
Your GVWR is 1313 lbs more than the curb weight of that Yukon XL. Your estimated tongue weight is 750 lbs, leaving you 563 lbs. If you put 30 gallons in the fuel tank, you are now down another 240 lbs, leaving only 323 lbs for all passengers and gear.

Curb weight includes fuel and all other fluids. Dry weight doesn't.

[DRTDEVL]

You are overthinking this by a lot. You have another problem staring you in the face, yet you don't even realize it.

Your GVWR is 1313 lbs more than the curb weight of that Yukon XL. Your estimated tongue weight is 750 lbs, leaving you 563 lbs. If you put 30 gallons in the fuel tank, you are now down another 240 lbs, leaving only 323 lbs for all passengers and gear.

Since you drive a Yukon XL and bought a bunkhouse trailer, I am assuming there are numerous kids involved? If you have 2 adults averaging 180 lbs in the front seats, that leaves -37 lbs
and we haven't even gotten into kids, snacks, their entertainment, luggage, etc.

You need a 3/4 ton SUV for this.