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gr8white

What PSI on Truck tires to pull my RV?

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I have a 2016 Sierra short bed Diesel and my tires are Michelin Defender LTX M/S LT265/60R20 Load Range E Max PSI 80.  I am about to do an 8 month trip around the country pulling an 8,000 lb tow behind RV.  I will be going through the dessert often.  What PSI would you put your front an back tires at?

Also, the tires on my travel trailer are load range D max 65 psi.  What PSI would you put on the tires in the RV?

Edited by gr8white

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Do you have axle weights for the front and rear of the truck and the trailer with everything hooked up and loaded for travel?  That should be your starting point.

Art

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Art,  I have never heard of axle weights.  Ive done a 2 year trip around the country with a 5th wheel and have never heard of them.  Although my new trailer is a pull behind. I know my RV wont be overloaded based on the sticker on the door and the truck is a diesel made to haul so that can pretty much haul anything. 

Edited by gr8white

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Next time you're near a truck stop with a "CAT Scale" run your truck and trailer loaded across the scale and get yourself weighed.  You will then know how much each of your truck axles is carrying and what your axles on your trailer are carrying. You will then have your "axle weights".  With these weights you can determine the correct tire pressure(s) for the load carried. 

Edited by DesertMiner

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I run MAX psi always

I load rocks up to supplement payload so I at MAX weight always

I try to run MAX speed always

Signed,

Max

 

Edited by noteven

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Nearly every tire manufacturer has a chart for recommended tire pressure for the load the tires are carrying.  As suggested earlier weigh your vehiclle axles loaded and check the charts.  These are cold tire pressures before driving.  

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4 hours ago, 2gypsies said:

Definitely weight your trailer fully loaded and a tank of fresh water to begin.

All passengers and gas tank full plus dogs.

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I really appreciate the advice.  I will definitely weigh myself but I need to set PSI before I do that because once I leave the top of the mountain that I am at, I wont come back until spring. .  Im thinking from what I have read, 70 (80 max psi) on the front truck tires and 73 on the back. The trailer I am thinking 60 all around (65 max PSI).  Would I be ok with that?

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Just to make sure you understand, all pressures are COLD inflation pressures.  Do not concern yourself with the pressures as the tires warm up and definitely DO NOT bleed air from the tires when they are warm to keep them below the 80 psi or 65 psi numbers. Put the pressure that your tow vehicle manufacturer says to inflate those tires for your maximum load capacity, and that may be something like 60 in the front and 70 in the rear, but do what the manual for the truck says.  On the trailer, the ST trailer tires can run at the max pressure on the sidewalls, and you say that is 65 psi.  If you inflate your tires to these numbers, you will have a good start.  Just do not under inflate the tires, because that will cause the tires to run hotter, and heat is bad for tires, whether they are on the truck or trailer.

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4 hours ago, 57becky said:

Just to make sure you understand, all pressures are COLD inflation pressures.  Do not concern yourself with the pressures as the tires warm up and definitely DO NOT bleed air from the tires when they are warm to keep them below the 80 psi or 65 psi numbers. Put the pressure that your tow vehicle manufacturer says to inflate those tires for your maximum load capacity, and that may be something like 60 in the front and 70 in the rear, but do what the manual for the truck says.  On the trailer, the ST trailer tires can run at the max pressure on the sidewalls, and you say that is 65 psi.  If you inflate your tires to these numbers, you will have a good start.  Just do not under inflate the tires, because that will cause the tires to run hotter, and heat is bad for tires, whether they are on the truck or trailer.

 

What he said.

Inflate truck front & rear tires to psi as indicated on the door (jamb) sticker - or owner's manual. Often the front tires are different (less psi)  than the rears.

Trailer tires to 65 psi.

Never exceed the max pressure (cold) as indicated on the tire sidewall.

~

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I inflate my truck and camper tires to the max psi on the side of the tire. I recall people stating that max inflation makes for a harder/rougher ride. If it does I have not found the ride uncomfortable in the least. So, forgetting about  the comfort issue,  what do you think are the consequences of max inflation? I suppose I am suggesting the OP inflate tires to max and be done with it. 

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3 hours ago, Friz said:

So, forgetting about  the comfort issue,  what do you think are the consequences of max inflation?

That would depend on the weight on each tire. An over inflated tire will wear the center of the tread out faster than the rest, even if it isn't too high pressure for the sidewalls. 

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On 10/15/2019 at 3:42 PM, Kirk W said:

Check out the Michelin truck tire inflation tables and find the proper inflation pressure based on 1/2 the amount of weight on each axle, adding 10% since you don't have individual wheel weights, which is a more accurate way to do this. 

I also have Defenders on my truck. The Michelin inflation table shows many Michelin tires, but Defenders are not one of them. A call to Michelin was absolutely no help at all.  I have Defender LTX M&S, they have LTX AT/2s but not M&S.

Edited by dzwiss

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1 hour ago, Kirk W said:

That would depend on the weight on each tire. An over inflated tire will wear the center of the tread out faster than the rest, even if it isn't too high pressure for the sidewalls. 

Okay, have heard about the center wear problem on over inflated tires. If the side of a tire says 85 psi max, how do you call it "over inflated" or "too high pressure at 85 psi?

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So you’re not planning on checking your tires for 8 months? 

22 hours ago, gr8white said:

I really appreciate the advice.  I will definitely weigh myself but I need to set PSI before I do that because once I leave the top of the mountain that I am at, I wont come back until spring. .  Im thinking from what I have read, 70 (80 max psi) on the front truck tires and 73 on the back. The trailer I am thinking 60 all around (65 max PSI).  Would I be ok with that?

 

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1 hour ago, Friz said:

Okay, have heard about the center wear problem on over inflated tires. If the side of a tire says 85 psi max, how do you call it "over inflated" or "too high pressure at 85 psi?

The max inflation pressure shown on the side of an LT or ST tire corresponds to the maximum load the tire is rated for.  As the load decreases below the maximum load, the recommended tire pressure also decreases. So if you choose to run max. pressure (which is the safe default if you don't know the weight) but your weight is actually well below max, the center of the tire will wear more quickly. 

So the tire is over-inflated for that load.

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13 hours ago, Friz said:

Okay, have heard about the center wear problem on over inflated tires. If the side of a tire says 85 psi max, how do you call it "over inflated" or "too high pressure at 85 psi?

 

12 hours ago, mptjelgin said:

The max inflation pressure shown on the side of an LT or ST tire corresponds to the maximum load the tire is rated for.  As the load decreases below the maximum load, the recommended tire pressure also decreases. So if you choose to run max. pressure (which is the safe default if you don't know the weight) but your weight is actually well below max, the center of the tire will wear more quickly. 

So the tire is over-inflated for that load.

Exactly... What is stated on the tire is for the maximum load and is the pressure that should never be exceeded as it is the upper pressure limit for the tire's design. 

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People often ponder over tire inflation pressures. Everyone seems to have a solution. This is how it’s advertised and supposed to be done. My reference material is from NHTSA, FMVSS & USTMA.

 

This is for all Original Equipment (OE) tires. “The correct inflation pressures” for them under, normal operating conditions is the vehicle manufacturer’s recommended cold inflation pressures found in the vehicle owner’s manual, on the tire placard and certified on the vehicle certification label. Conditional deviations may be provided on a vehicle manufacturer’s label for special conditions such as towing. The vehicle owner’s manual is the place to look for vehicle manufacturer deviations.

 

When OE tires have some reserve load capacities available, optional inflation pressures between what has been recommended and what may be used to provide maximum load capacity from the tire are always optional. Gray area if you prefer.

 

Load inflation charts are standardized per designated tire sizes. They do not provide recommendations. They are a tool used by manufacturers and other experienced installers to determine a correct tire inflation.

 

Automotive tires MUST provide load capacity reserves. Manufacturers usually increase the vehicles GAWR values to provide the tire load capacity reserves. RV trailer tires are required by regulation to provide a load capacity equal to or greater than the vehicle certified GAWRs. It has proven to be flawed but still exists. RIVA has stepped in and require all of their participation members – about 98% of all USA RV trailer builders – to provide OE tires with at least 10% of load capacity reserves above GAWR axle maximum loads.

 

The USTMA mentions in their procedures manuals a procedure to inflate RV tires to a load carried. However, they protect that statement with the caveat; “Never inflate tires below the vehicle manufacturer’s cold recommendations”.

 

Because FMVSS (standards) are minimum, OE tire Designated sizes are considered by USTMA to be the minimum standard and protect that standard with the caveat; “Replacement tires MUST not be smaller than the OE tires and they MUST provide a load capacity equal to the OE tires”. Of course when the designated size is changed, the placards are no longer valid. A new cold recommended inflation pressure must be established that provides a load capacity for the replacement tires equal to or greater than the OE tires provided. NHTSA allows an auxiliary placard for that information. The installer should put the new information on a placard and place it adjacent to the original placard. The installer should inform the vehicle owner of the new recommended cold inflation pressures so the vehicle owner’s manual can be updated.

 

On RV trailers with recommended cold inflation pressures equal to the tire maximum for the load, there are no inflation options other than maximum. Or, install tires with a higher load range, if possible. They will conform to the certification label but have load capacity deserves higher than the lower load ranged tire.

 

Bottom line: Vehicle recommended inflation pressures for OE tires are the correct inflation pressures. If you have a load higher than what the OE tires provide, your axle is overloaded.     

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On 10/15/2019 at 2:22 PM, gr8white said:

Art,  I have never heard of axle weights.  Ive done a 2 year trip around the country with a 5th wheel and have never heard of them.  Although my new trailer is a pull behind. I know my RV wont be overloaded based on the sticker on the door and the truck is a diesel made to haul so that can pretty much haul anything. 

Tires_, you will find your truck to be much more stable when towing, with the tires aired up to sidewall listed max. air pressure, sure the ride may be harsher, but I found the increase in handling/stability more than offsets the ride factor. ST trailer tires are usually operating at or near their maximum weight capacity, thus should also be ran at sidewall listed maximum air pressure.  Carlisle ST tire warranty used to state if tires were not operated at sidewall maximum it voided the warranty.

An aside, if a tire warranty claim is presented, and the tire mfgr determines the tire was under-inflated,, said claim will be denied.

Axle weights; each axle has a maximum weight capacity, tires on this axle also have a total maximum weight capacity, the lesser of those two determine maximum axle weight.

 

Edited by Ray,IN

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6 hours ago, Ray,IN said:

 

Axle weights; each axle has a maximum weight capacity, tires on this axle also have a total maximum weight capacity, the lesser of those two determine maximum axle weight.

 

The official load for an axel is determined by the vehicle manufacturer and displayed on the vehicle certification label as GAWR. OE tires NEVER provide, a load via recommended cold inflation pressures less than GAWR.  

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The way I understand this is that the ideal tire contact patch occurs when the tire pressure matches the load on the tire, as per the manufacturer's weight chart.  Tire wear and traction are optimal when at this point.  Under inflation is always worse than over inflation and one should err to the higher pressure side.  RV manufactures may install tires rated above the rating of an axle.  Running at sidewall pressure in these cases is definitely higher than needed, but still better than under inflation.  Running through a CAT scale to get at least axle weights is pretty easy.  If tire position weights are not known, the best temporary practice is to run the tire at the max cold pressure listed on the tire sidewall.  Never inflate tires above their listed sidewall pressure (cold).

Note, that without weighing,  tires/axles can be overloaded without knowing it.

Art

Edited by SKP073615

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1 hour ago, SKP073615 said:

The way I understand this is that the ideal tire contact batch occurs when the tire pressure matches the load on the tire, as per the manufacturer's weight chart.  Tire wear and traction are optimal when at this point.  Under inflation is always worse than over inflation and one should err to the higher pressure side.  RV manufactures may install tires rated above the rating of an axle.  Running at sidewall pressure in these cases is definitely higher than needed, but still better than under inflation.  Running through a CAT scale to get at least axle weights is pretty easy.  If tire position weights are not known, the best temporary practice is to run the tire at the max cold pressure listed on the tire sidewall.  Never inflate tires above their listed sidewall pressure (cold).

Note, that without weighing,  tires/axles can be overloaded without knowing it.

Art

Because you have a bus you may see inflation pressures differently from FMVSS standards. That’s because of so much disinformation about tire inflations for such vehicles. Many feel its ok for them to use FMCSA regulations in place of FMVSS standards because of the use of commercial tires. FMCSA regulations are not applicable to FMVSS standards. The vehicle certification process of the final stage manufacturer is the factor to consider when applying tire inflation pressures. If there is no provision in your vehicle’s owner’s manual or an auxiliary tire information placard for optional inflation pressures and the federal certification label lists recommended cold inflation pressures for the OE tires, that information is correct and the FMVSS outlaying the maintenance for those standards is FMVSS.

 

 

The following information is a verbatim quote from a USTMA  publication about proper inflation of motor home tires fitted using FMVSS.

 

 

“Determining Proper Inflation Pressure Use of the tires, wheels, and inflation pressures as specified on the vehicle tire placard, certification label or in the service manual ensures that these components can carry the maximum rated axle loads (GAWR) and maximum vehicle weight (GVWR), and also maintains other performance characteristics, if any, intended by the vehicle manufacturer.  At a minimum, the tires on each axle should not be over loaded or under inflated if the vehicle is properly loaded.

With actual weights of the loaded RV acquired by weighing, it is possible to compare them against the GAWR, GVWR, and tire capacities posted on the vehicle tire placard or certification label. These actual weights are also what should be used to determine any increase in inflation pressure for the tires, if required.

Inflation pressure recommendations may also be determined based on the tire manufacturer’s specifications, which define the amount of inflation pressure necessary to carry a given load. These inflation pressures may differ from those found on the vehicle tire placard or certification label.

However, never use inflation pressure lower than specified by the vehicle tire placard, certification label or owner’s manual. Nor should inflation pressure exceed the maximum pressure molded on the tire sidewall."

Edited by TireHobby

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7 hours ago, TireHobby said:

The official load for an axel is determined by the vehicle manufacturer and displayed on the vehicle certification label as GAWR. OE tires NEVER provide, a load via recommended cold inflation pressures less than GAWR.  

Correct! We said the same thing using different words.

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