Tire pressure?

[sourdough]

I believe my post #19 led to some confusion for OP.

I stated airing up from the placard indicated 65psi for the rear tires. What I stated is what I would do for the reasons I said I would do it. I did not clarify why. To further confuse the issue for the OP; the inflation charts being referenced are what I consider "guidelines" from over the years. In this case I don't like a heavy trailer pin in the bed of the truck bouncing when I know the max weight the truck is being subjected to will exceed the static weight when it's just sitting, therefore I air up. I use the same philosophy on my trailer tires and have stated that many times - I will not use the static (sitting) weight minus the pin weight because that is just not what those tires will be subjected to.

For the OP; use the pressures indicated on the placard. Place the trailer fully loaded on the truck. Put a nice thick chalk line on those rear tires then pull forward with the truck until those tires rotate and leave a chalk line on the pavement. How much tread is left on the pavement? What does it look like? In post #27 Russ provided some pics of what various stages of pressure "look like". The "correct" illustration is not what I look for. I look for that chalk line to be as even as possible across the tread when it's left on the pavement and arching a little toward that "correct" bow as indicated. You might get that at 65 psi, and hopefully you will, but I have my doubts. The pin weight will have a lot to do with it. I have never had a set of tires on anything wear down in the middle.

All that to say, for simplification purposes, just air up to the pressures on the placards and proceed. You can fine tune later. Nothing is going to explode if you're off 5/10psi until you get it all figured out.

[flybouy]

For me personally I air up the trailer to max psi listed on the sidewall of my E rated tires vs the placard for the OEM D rated tires. My truck has E rated tires and I inflate the rear tires about 10 psi higher than placard when towing the trailer. Both placards state "minimum" tire inflation and not ONLY INFLATE TO..." A little background, I'm 68 yrs old. I've been driving since I could see over the dashboard while setting in my father's lap.. I think I was "helping" him work on cars from a younger age. After having driven a variety of vehichles and towing utility trailers, boats, campers, etc. I have yet had a tire wear unevenly due to improper inflation.

I've typically been a "follow the mfg recommendations" guy but here's where I differ. The last several decades have be fraught with litigation and government pressures as a result. All one has to do is look at the warning labels on any electrical device, read any manual ( Chinese products not included) and there will be a "dumbed down" warn them of everything and CYA to keep the lawyers happy. By the time the manual or information label reaches the consumer its often been altered by several law departments, possibly a consumer advocacy group and some government agencies.

It used to be you could "read between the lines" and throw out the chaff and use some logic and common sense to get to the wheat. Now days the younger generations have fewer life experiences to fall back on and if they can't find a video to tell them what to do they are lost. Not hateing on anyone, just an observation.

[Pathman]

Thanks, appreciate the further insight and the chalking process, I’ll give it a try.

FlyB, I’m a few years younger than you and put in 42 years on the railroad as an inspector, so I have a very similar mindset to you, and plenty of mechanical experience, but I still defer to seasoned guys in areas I’m not familiar with, that’s a throw back to my apprentice days starting on the RR.
Anyway, I’ll navigate all the input here, and come to a common sense conclusion.

Thanks.

[sourdough]

I failed to mention in my last post that with the chalk you can also just look at the tires to see where it wears off and what's left to see how the tire is contacting the road. It might be easier to see that way vs the pavement if you have lighter colored pavement.

[Pathman]

Copy that.

[wrvond]

Originally Posted by Pathman

So what tire pressure do you all use while towing? Is the max pressure recommended?

My truck door sticker indicates 70 front and 65 rear. That’s what I run all the time. I’ve got nearly 300,000 miles on this truck and average 85,000 miles per set of tires.
I once tried lowering the front pressures but it didn’t improve the ride noticeably so I went back to Ford’s recommended pressure. The inner rear tires are too difficult to reach to be jacking around with their pressures.

The sidewall states:
Max load single 3195 lbs. @ 80 psi
Max load dual 2190 lbs. @ 80 psi

Interestingly my front GAWR is 5600 lbs. and rear GAWR is 9900 lbs.
If you add the values @ 80 psi you come out with 6390 front and 8760 rear.
It would seem obvious that some other component(s) restrict the front GAWR to less than the sidewall would indicate but I am at a loss to explain how the rear GAWR is way more than the sidewall data indicates.

[wiredgeorge]

Originally Posted by travelin texans

Actually in 300+k miles 10+ years full-time towing a 16.5k lb 5th wheel I used the placard inflation pressures for the truck & the inflation for max on the sidewall of whatever size tire were on the rv at any given time, never an issue with any tires in that 300+k miles.
I did weigh the setup at each individual wheel location a couple of times & several times truck & rv separately, but with all those weights I never changed the inflation rates on any tire & was always within the limits of each tire & all other weights of truck & rv.
I would rather run any tire a bit over inflated rather than under. Under inflation causes heat which is very detrimental to tires as well as causing drag lowering fuel mileage & causing handling issues with squirmy tires.
I would never run any tire below the placard inflation recommendations or above the inflation imprinted on the sidewall of the tire, with these 2 pressures there's about 10-15 lb spread that should work for any tire, loaded or unloaded.
Pathman, Other than my experiences here I don't know how to help you further understand!

Calm down ol' fella! Was just funnin...

[gearhead]

I thought all Fords came from the factory with shimmy. That wagon era twin front I beam.

When empty I run the rears at 42. I always run the fronts at 80, I mean rules are rules.

[sourdough]

OP remember that some pressures referenced are for DRW trucks so they will differ. Look at the signature of the post to see (if it's there).

[bsmith0404]

Originally Posted by wrvond

The sidewall states:
Max load single 3195 lbs. @ 80 psi
Max load dual 2190 lbs. @ 80 psi

Interestingly my front GAWR is 5600 lbs. and rear GAWR is 9900 lbs.
If you add the values @ 80 psi you come out with 6390 front and 8760 rear.
It would seem obvious that some other component(s) restrict the front GAWR to less than the sidewall would indicate but I am at a loss to explain how the rear GAWR is way more than the sidewall data indicates.

The weakest component, in this case the tires, only have to be high enough to meet GVWR. The tires do not have to add up to GAWR if the GAWR exceeds what is required for GVWR.

[bsmith0404]

A lot of different opinions here and a lot of them point back to the door sticker or placard on the RV. The reason I don’t use those is because I don’t have the original size tires that are listed on those still installed on the truck or trailer. If you still have OE or OE equivalent tires, the pressures listed on those works just fine and no reason to over think it. If you have changed tires, then it requires a little more thought, testing, or math to make sure the pressures you use will carry the load you place on them and not leave the tire in an over/under inflated contact patch. A full contact patch from a properly inflated tire gives you better control and improved acceleration and stopping. I also carry a tread depth gauge in my truck and check the tire wear on a regular basis to make sure I’m getting even wear across the tire. That is a good indicator of a full/even contact patch.

[Pathman]

So I checked the manual for my Ram. It clearly states that the recommended psi on the door jamb is for any and all weights.

[CWtheMan]

There are different ways the vehicle manufacturer of your tow vehicle can provide the mandatory load capacity reserves. It is almost always done with certified GAWRs. Tires are fitted to provide a load capacity equal to or greater than GAWR requirements. So, you have GAWRs that are providing excess load capacity to support the GVWR, thus the required load capacity reserves for the vehicle are met.

The recommendations on the vehicle certification label are MINIMUM standards. To use less tire inflation pressures than what is recommended is never recommended. The USTMA, who write their standards to ensure minimums are met, publish a statement that says to NEVER use less inflation pressures than recommended by the vehicle manufacturer for OE tires.

This is an excerpt from the FMVSS document: The sum of the maximum load ratings of the tires fitted to an axle shall not be less than the GAWR of the axle system as specified on the vehicle's certification label. When the certification label shows more than one GAWR for the axle system, the sum shall be not less than the GAWR corresponding to the size designation of the tires fitted to the axle.

The only restrictions for inflating tires to a higher load capacity than recommended, are to ensure the wheels and valve stems can support the increased PSI settings. The option ends with a warning to never exceed the cold inflation pressure used to gain maximum load capacity from the tires.

[Pathman]

“The only restrictions for inflating tires to a higher load capacity than recommended, are to ensure the wheels and valve stems can support the increased PSI settings. The option ends with a warning to never exceed the cold inflation pressure used to gain maximum load capacity from the tires.”

Taking this excerpt from your comments CW, how is one to know if a tire or valve can handle the additional PSI?
The majority of the public (and from the recommendation of many here), will be using the information on the vehicle placards and the owners manuals, so although the info you’re providing may be technically correct (?), what would give the average RV’er the assurance that deviating from the manufacturers recommendations will be a safe approach?

[rhagfo]

Originally Posted by wrvond

My truck door sticker indicates 70 front and 65 rear. That’s what I run all the time. I’ve got nearly 300,000 miles on this truck and average 85,000 miles per set of tires.
I once tried lowering the front pressures but it didn’t improve the ride noticeably so I went back to Ford’s recommended pressure. The inner rear tires are too difficult to reach to be jacking around with their pressures.

The sidewall states:
Max load single 3195 lbs. @ 80 psi
Max load dual 2190 lbs. @ 80 psi

Interestingly my front GAWR is 5600 lbs. and rear GAWR is 9900 lbs.
If you add the values @ 80 psi you come out with 6390 front and 8760 rear.
It would seem obvious that some other component(s) restrict the front GAWR to less than the sidewall would indicate but I am at a loss to explain how the rear GAWR is way more than the sidewall data indicates.

Well I think you need to check your side wall again!
Our 2036 Ram DRW the 235/80-17 tire have a single rating of 3,195, and a dual rating of 2,835. thus giving the total at 80 psi 11,340#. Our Ram's rear axle is rated at 9,750# that is why the 65 psi inflation.

[CWtheMan]

Originally Posted by Pathman

“The only restrictions for inflating tires to a higher load capacity than recommended, are to ensure the wheels and valve stems can support the increased PSI settings. The option ends with a warning to never exceed the cold inflation pressure used to gain maximum load capacity from the tires.”

Taking this excerpt from your comments CW, how is one to know if a tire or valve can handle the additional PSI?
The majority of the public (and from the recommendation of many here), will be using the information on the vehicle placards and the owners manuals, so although the info you’re providing may be technically correct (?), what would give the average RV’er the assurance that deviating from the manufacturers recommendations will be a safe approach? There is no safe "approach" unless recommended by the vehicle manufacturer. Reading the Keystone owner's manual will support that statement.

Let's say your trailer has OEM tire sized at ST225/75R15 with a LRC. The trailer manufacturers purchase their wheel assemblies completely assembled. Their instructions to the OEM provider is not going to provide specifications above what is necessary for a proper fitment to the vehicle. So, the entire wheel assemblies will only be required to provide the minimum load capacity needed by the trailer builder.

Now, the consumer wants to upgrade to a LRE. That will require valve stems that will support the increased PSI needed so the tire can provide more load capacity. At the same time the wheels must be checked for a PSI limit. Most of the OEM providers will have their wheels with a molded wheel maximum load capacity and maximum PSI capacity. The consumer is not worried about the OEM wheel load capacity because it will be appropriate for the OEM wheels and the consumer is not changing the vehicle certified GAWRs. However the wheel MUST have the ability to withstand any PSI increase to support the requirements of the LRE tires.

That information is not normally available in the trailers owner's manuals because the manufacturer did not/will not recommend any tires other than what they installed.

https://www.tirerack.com/tires/tiret...c300ad0a82b82d

[Pathman]

Originally Posted by CWtheMan

Let's say your trailer has OEM tire sized at ST225/75R15 with a LRC. The trailer manufacturers purchase their wheel assemblies completely assembled. Their instructions to the OEM provider is not going to provide specifications above what is necessary for a proper fitment to the vehicle. So, the entire wheel assemblies will only be required to provide the minimum load capacity needed by the trailer builder.

Now, the consumer wants to upgrade to a LRE. That will require valve stems that will support the increased PSI needed so the tire can provide more load capacity. At the same time the wheels must be checked for a PSI limit. Most of the OEM providers will have their wheels with a molded wheel maximum load capacity and maximum PSI capacity. The consumer is not worried about the OEM wheel load capacity because it will be appropriate for the OEM wheels and the consumer is not changing the vehicle certified GAWRs. However the wheel MUST have the ability to withstand any PSI increase to support the requirements of the LRE tires.

That information is not normally available in the trailers owner's manuals because the manufacturer did not/will not recommend any tires other than what they installed.

https://www.tirerack.com/tires/tiret...c300ad0a82b82d

I copy that, however, I didn’t inquire about changing tires from the OEM tires, I simply asked if it’s appropriate (and what the GP is) to “air up” when towing.

I appreciate your time and info provided, but when you seasoned guys go off topic, un newbies are lost, just sayin…

[bsmith0404]

Originally Posted by Pathman

I copy that, however, I didn’t inquire about changing tires from the OEM tires, I simply asked if it’s appropriate (and what the GP is) to “air up” when towing.

I appreciate your time and info provided, but when you seasoned guys go off topic, un newbies are lost, just sayin…

Sometimes it seems like we may be going off topic or providing useless information, however everyone who reads this won’t have the same situation. The additional information we provide may be helpful to them. It may also be helpful for you down the road if you ever decide to upgrade tires. We’re simply trying to educate you so you understand why vs just answering your question without the reasoning behind it.

[Pathman]

I can appreciate that BS, and if I ever change tires I’ll look back to this post.

[wiredgeorge]

Originally Posted by Pathman

I can appreciate that BS, and if I ever change tires I’ll look back to this post.

I get the BS! That's kind of funny! Hey Mr. Smith, aka BS....