Good Sam Club Open Roads Forum: Looks like 30psi ought to be plenty good for towing
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Towing

Open Roads Forum  >  Towing

 > Looks like 30psi ought to be plenty good for towing

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Next
chrispitude

Allentown, PA

Senior Member

Joined: 05/20/2007

View Profile


Offline
Posted: 06/23/18 04:55pm Link  |  Quote  |  Print  |  Notify Moderator

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:

[image]

The manual doesn't say much about the label:

[image]

It mentions a bit about not underinflating or overinflating:

[image]

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":

[image]

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?

lawrosa

Howell NJ

Senior Member

Joined: 10/06/2013

View Profile



Posted: 06/23/18 05:10pm Link  |  Quote  |  Print  |  Notify Moderator

My p rated tires are 44psi max. I run 40 psi in them all the time..

If I had XL tires I would also run 40 psi in them..

No these tires do not work like LT tires where the more you inflate the more load you can carry.

But thats me.


Mike L ... N.J.

2006 Silverado ext cab long bed. 3:42 rear. LM7 5.3 motor. 300 hp 350 ft lbs torgue @ 4000 rpms
2018 coachmen Catalina sbx 261bh


carringb

Corvallis, OR

Senior Member

Joined: 07/28/2003

View Profile


Offline
Posted: 06/23/18 05:11pm Link  |  Quote  |  Print  |  Notify Moderator

What's your rims rated for?


Bryan

2000 Ford E450 V10 VAN! 450,000+ miles
2014 ORV really big trailer
2015 Ford Focus ST


chrispitude

Allentown, PA

Senior Member

Joined: 05/20/2007

View Profile


Offline
Posted: 06/23/18 05:24pm Link  |  Quote  |  Print  |  Notify Moderator

carringb wrote:

What's your rims rated for?


I have no idea. They're the factory GMC 20" peely-chrome wheels. That's another reason I'm not too keen on throwing 50psi in the rears to see what happens.

mike-s

Michigan

Senior Member

Joined: 10/23/2006

View Profile


Offline
Posted: 06/23/18 06:00pm Link  |  Quote  |  Print  |  Notify Moderator

P275/55*20 is good for 2216 lbs per tire at 29 psi. So, about 4500 lb on the rear axle @30 psi. What's the RAWR? If less than about 4500 lbs, more pressure won't get you more capacity. And, I'll bet it's right around 4500 lbs - manufacturers spec tires and pressures to support the ratings they give. If the sidewall max pressure allows it, I might run an extra 5 psi when towing, but not more for treadlife.

chrispitude

Allentown, PA

Senior Member

Joined: 05/20/2007

View Profile


Offline
Posted: 06/23/18 07:06pm Link  |  Quote  |  Print  |  Notify Moderator

mike-s wrote:

P275/55*20 is good for 2216 lbs per tire at 29 psi. So, about 4500 lb on the rear axle @30 psi. What's the RAWR? If less than about 4500 lbs, more pressure won't get you more capacity. And, I'll bet it's right around 4500 lbs - manufacturers spec tires and pressures to support the ratings they give. If the sidewall max pressure allows it, I might run an extra 5 psi when towing, but not more for treadlife.


The sticker is missing on the door (thanks previous owner), but AFAIK the GFAWR is 3600 lbs and GRAWR is 4000 pounds.

You're thinking 35psi front and rear, instead of 35psi front and 40psi rear?

mike-s

Michigan

Senior Member

Joined: 10/23/2006

View Profile


Offline
Posted: 06/23/18 07:24pm Link  |  Quote  |  Print  |  Notify Moderator

chrispitude wrote:

The sticker is missing on the door (thanks previous owner), but AFAIK the GFAWR is 3600 lbs and GRAWR is 4000 pounds.

You're thinking 35psi front and rear, instead of 35psi front and 40psi rear?
? The picture of the placard you posted says 30/30, not sure where your "instead of" 35/40 comes from.

I was thinking 35 rear, instead of the 30 on the label. But if the rear axle rating is 4K, the tires will support 500 lb more than that even at 30, so there's already a good margin.

Probably best to stop by a CAT scale with your Yukon empty, just to get an idea of where it sits normally. That will give you a good feel for how much tongue weight and load you can add.

Or, if you contact GM (or maybe even the dealer), and explain that the capacity placard is missing, they might be able to give you the numbers based on the VIN.

HadEnough

Traveling. Always.

Senior Member

Joined: 04/17/2016

View Profile


Offline
Posted: 06/23/18 07:44pm Link  |  Quote  |  Print  |  Notify Moderator

It's simple. Ignore everything except the max pressure on the tire sidewall.

Put the load on and look at the tires. The entire part of the tire that makes contact with the road (the tread profile) should be making contact. If it's bulging at the sidewall and the tread is only making contact at the edge, you are underinflated for the load. If the center of the tread profile is making contact, but the edges aren't, you have too much pressure.

Tire inflation is only a matter of getting the tire shape correct. Put as much air in as you need to get the shape correct, without exceeding the maximum pressure shown on the tire sidewall.

See these pictures for a visualization.

Tire inflation profile pictures

It's way, way easier than all those stickers on the vehicle confuse you (and a lot of repair shops) into thinking.

BurbMan

Islip, Long Island

Senior Member

Joined: 09/20/2001

View Profile



Good Sam RV Club Member


Posted: 06/23/18 08:16pm Link  |  Quote  |  Print  |  Notify Moderator

This is all guesswork....when you get the trailer, hook it up, go to the scales, and get some real numbers on axle weights. THEN you will know how to inflate the tires to carry the load.

It should be noted that the door sticker says that the tires will carry the GVWR at 30 psi. You shouldn't need to inflate past that unless you are exceeding the GVWR, right? Again, just guessing without the scale #'s.


2001 Suburban 2500LT 8.1L/4.10
2008 Terry TT
Hensley Arrow Hitch
Dill TPMS, CorrecTrack alignment, LT tires


mike-s

Michigan

Senior Member

Joined: 10/23/2006

View Profile


Offline
Posted: 06/23/18 08:17pm Link  |  Quote  |  Print  |  Notify Moderator

HadEnough wrote:

It's simple. Ignore everything except the max pressure on the tire sidewall.

Put the load on and look at the tires. The entire part of the tire that makes contact with the road (the tread profile) should be making contact. If it's bulging at the sidewall and the tread is only making contact at the edge, you are underinflated for the load. If the center of the tread profile is making contact, but the edges aren't, you have too much pressure.

Tire inflation is only a matter of getting the tire shape correct. Put as much air in as you need to get the shape correct, without exceeding the maximum pressure shown on the tire sidewall.

See these pictures for a visualization.
Well, no, judging by eye is probably the worst thing you can do. Are you really claiming that you've ever seen a tire which is making contact only at the edges (excepting one with zero pressure), or that you've seen the edges not making contact without it being vastly overinflated? There's a wide range where you have full contact, but the pressure will be wrong.

Use the manufacturer's recommendations, followed by the load tables. To figure it out independently, you need to travel a while under load, then quickly and accurately measure the tread temperature across the width, like the racers do.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Next

Open Roads Forum  >  Towing

 > Looks like 30psi ought to be plenty good for towing
Search:   Advanced Search

Search only in Towing


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2018 CWI, Inc. © 2018 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS