tire pressure on fifth wheel

[SMR]

OK so my friend suggests that I should set the cold tire pressure 10 psi below the recommended tire pressure of 110 psi to allow for heat and added psi while traveling.
the low is 70 and the high during travel will be 90- I have always been advised and have always set the cold pressure on both the truck and trailer to what is the recommended psi. this is the first time I have traveled in this heat and am not sure if his thoughts are correct or not.

what do you all recommend to set the psi at?

thanks

 

[2kGeorgieBoy]

Are you talking about the "max" pressure listed on the tire sidewall or the recommended pressure by the vehicle manufacturer? When you lower the  tire pressure, you lower  the load capacity of the tire. Tires have a built in safety margin over and beyond the max pressure listed on the sidewall.

 

[Larry N.]

The tire companies allow for the heating effects of sun and travel when setting cold pressure recommendations. You don't need to make adjustments for that. If you can get each axle weighed (better yet, each wheel), then you can use the tire manufacturer's pressure chart to find what they recommend for that weight.

 

[SMR]

Thanks I will set them as I always have. I use the psi set by the camper manufacturer. I will be getting everything weighed at the escapees rally.

 

[Arch Hoagland]

As you lower your tire pressure the tire will heat up more.

That's how I look for a tire low on air pressure when I check mine with an IR gun.  A tire lower than the others will read a higher temperature. More flexing going on.

When I pulled a trailer I always set the tire pressure to the max stated on the sidewall of all the tires.

 

[terontale]

I asked my dealer this question. The service guy said to run whatever is on the sidewall. We have a 2005 Mt. Rushmore. My sidewalls call for 110lbs. This is what we run in them. We have made several trips to the beach and have not had a problem.

 

[Larry N.]

The service guy said to run whatever is on the sidewall.

That pressure on the sidewall is a "do not exceed" pressure, not a recommended running pressure.

 

[Gary RV_Wizard]

That pressure on the sidewall is a "do not exceed" pressure...

Not even that. It's the pressure needed to carry the tires max rated load. It is permissible to exceed that and tire makers may even recommend 10-15 psi above that for specific situations.

However, the real world situation is that few trailer have tires with any reserve weight capacity, so the tire is always running at or very near its max load weight. Given that, using the max load pressure shown on the sidewall is practical advice for a typical travel trailer or 5W.  It is not, however, a general rule for all tires or all situations.

 

[xrated]

OK so my friend suggests that I should set the cold tire pressure 10 psi below the recommended tire pressure of 110 psi to allow for heat and added psi while traveling.
the low is 70 and the high during travel will be 90- I have always been advised and have always set the cold pressure on both the truck and trailer to what is the recommended psi. this is the first time I have traveled in this heat and am not sure if his thoughts are correct or not.

what do you all recommend to set the psi at?

thanks

Your best bet is to find the sticker/plaquard that is on the trailer and run the pressure that the trailer manufacturer recommends for that trailer.  That pressure, by the trailer manufacturer, takes into account the tire ratings (load capacity at that pressure) and of course the GVWR of that trailer!  Remember though, if you own a trailer that was bought used, someone before you may have changed the tires, so make sure that those tires provide a load capacity at the recommended pressure, that is equal to or exceeds the original tire's load capacity.

 

[grashley]

To add to xrated, check the load rating on your tires.  This should exceed the axle ratings and 80% of the GVWR (the other 20% is on the pin).  If the tire load ratings (capacity) is significantly greater than the actual weight being carried, pressures can be lowered according to the manufacturers load / pressure tables.  It will give a softer ride for the FW.  There is no NEED to lower pressures, but there is no harm within these parameters.

 

[John From Detroit]

Ok, As others have said Tire Pressure and the load the tire are carrying are related. Three pressures all but guaranteed to be wring are:
The one the Tire store pumps 'em up to
The one on the sticker inside the RV
The one modlded into the side wall (As others have said that is the maximum COLD pressure for the maximum load (Cold is like 70 ish) HOT it will be highre.

How to determine the proper pressure.
Get wheel weights (if duals both tires are one wheel) and use the tire maker's chart to find out what the proper pressure is. Instructions are in the forum library if you need help.

NOTE that both sides may be different.

Why is proper infoation improtant.

Too little pressure and the tires wear on the edges, the center does nto wear out. side wall flexing is increased which leads to earlier tire failure and less control when cornering.

Too much pressure and ONLY the center wears, the edges do not grip the road which again leads to a tendency to "Slide" due to not enough contact with the road.

Both cases are bad

proper inflation the enire tread contacts the road, Maximum control. Maximum tire life.

One thing some folks have suggested (I prefer scales) is to chalk the tire, like parking enforcement does, clear across the tread, then drive a SHORT distance and see if the chalk is evenly worn off. If you still have chalk in the center but the edges are gone, add air, if chalk at the edges but center gone, release air, if all gone try again but don't drive so far. if all half gone.> Read and note pressure.. it's proper.

 

[FastEagle]

Tire inflation pressures for RV trailers is an ongoing - sometimes hot - topic on internet RV forums.

Some here have hit the nail on the head and others keep missing a few blows. Then there are the ones that confuse commercial inflation policy with every-day automotive standards.

It?s a confusing subject if you don?t know all the facts. In fact, you can have a correct solution that just isn?t an acceptable standard because of litigators.

So, I?ll first look at that. The answer is simple and right in front of all of us. It?s the vehicle?s certification label. That label represents a signed document where the vehicle manufacturer has sworn to the governing body (DOT) that ?This vehicle conforms to all applicable Federal motor vehicle safety and theft prevention standards?. On the date of certification. The standards to which they refer to for trailer tires are minimum. That makes the recommended inflation pressures found on the certification label MINIMUM.

The tire industry supports - what I call - the golden inflation rule. NEVER use less inflation pressure for your original equipment tires than what has been recommended by the vehicle manufacturer. For conformation of that rule you can read page 44 in the attached reference.

Inflation pressures between what has been recommended and what is needed to get the maximum load capacity from the tire are optional.

When using replacement tires that do not conform to the load inflation chart for the OE tires, a new recommended cold inflation pressure must be found for them. Their minimum load capacity must equal the load capacity the OE tires provided. An auxiliary tire placard may be used to display the new tire size and recommended inflation pressures.

https://www.ustires.org/sites/default/files/CareAndService_PassengerAndLightTruckTires.pdf

NOTE: When you open the document above, you're first impression may be to click out of it because it looks like the wrong thing for RV tires. Page 44 is in chapter #4. It's all about RV tires.

 

[Gary RV_Wizard]

The tire industry supports - what I call - the golden inflation rule. NEVER use less inflation pressure for your original equipment tires than what has been recommended by the vehicle manufacturer. For conformation of that rule you can read page 44 in the attached reference.

One of the litigation-based rules you mentioned.

 

[FastEagle]

One of the litigation-based rules you mentioned.

It's hard to be short with an answer for that.

Vehicle certification is a sworn statement from the trailer manufacturer to the governing body (DOT).

On the vehicle certification label the vehicle manufacturer makes a statement that the vehicle conforms to all Federal Motor Vehicle Safety Standards.

The FMVSS are minimum standards, within the standards the vehicle manufacturer is directed to insure the tire fitment is appropriate. To make it appropriate the vehicle manufacturer must set a recommended cold inflation pressure, also directed in the standard.

Can you see where that is going? Everything there is considered minimum. Doing less is unsafe.

 

[Gary RV_Wizard]

I was referring to your "golden inflation rule, the statement I quoted.  The tire manufacturers state that rule so that the trailer mfgr is solely responsible for setting the psi recommendation. They do that because the tire mfgrs do not want any legal responsibility for improper psi values. This all began with a series of lawsuits against tire makers, of which the Ford rollover fiasco was the most notable. However, lawsuits against Toyo for inadequate pressures that were actually prescribed by Country Coach mostly led to the present "golden inflation rule" as applied to RVs.

I have to disagree that the pressure recommended by the RV maker is the minimum. It is a recommendation they are required to provide, but whether it is a minimum psi or not is a legal liability concern, not a technical assessment.  To protect their own legal carcasses, the RV makers have little choice but to make a recommendation that is adequate for  a fully loaded trailer, simply because they have no way to predict the actual loading. That does not translate as "minimum" to me, but I'm an engineer.  Lawyers probably see it differently differently.  As I'm sure Fast Eagle does as well.

 

[FastEagle]

I was referring to your "golden inflation rule, the statement I quoted.  The tire manufacturers state that rule so that the trailer mfgr is solely responsible for setting the psi recommendation. They do that because the tire mfgrs do not want any legal responsibility for improper psi values. This all began with a series of lawsuits against tire makers, of which the Ford rollover fiasco was the most notable. However, lawsuits against Toyo for inadequate pressures that were actually prescribed by Country Coach mostly led to the present "golden inflation rule" as applied to RVs.

I have to disagree that the pressure recommended by the RV maker is the minimum. It is a recommendation they are required to provide, but whether it is a minimum psi or not is a legal liability concern, not a technical assessment.  To protect their own legal carcasses, the RV makers have little choice but to make a recommendation that is adequate for  a fully loaded trailer, simply because they have no way to predict the actual loading. That does not translate as "minimum" to me, but I'm an engineer.  Lawyers probably see it differently differently.  As I'm sure Fast Eagle does as well.

Minimum does need more explanation. However the standards are minimum requirements. We all know there are exceptions. Normal exceptions will be in the vehicle owner?s manual, mandated by NHTSA.

The tire industry supports the vehicle manufacturer?s  recommended cold inflation pressures as minimum.

NHTSA stipulates that the vehicle manufacturer has the sole responsibility for setting recommended cold inflation pressures for all Original Equipment tire fitments.

SAFECAR, a NHTSA publication, says the recommended cold inflation pressures found on the vehicle certification label, tire placard, and in the vehicle owner?s manual is the CORRET inflation pressure.

The optional range is between what has been recommended and what is needed for maximum load capacity. Some of the antidotal recommendations about the optional pressures are muddied by mixing FMVSS standards with Federal Motor Carrier regulations. One is not applicable to the other. 

This is the way the standard is worded for the information to be put on the certification label.

Tires: The size designation and the recommended cold inflation pressure for those tires such that the sum of the load ratings of the tires on each axle is appropriate for the GAWR.

 

[scottydl]

There is obviously a lot of information about... here's what I do, based on what I've learned here:

I have always been advised and have always set the cold pressure on both the truck and trailer to what is the recommended psi.

Trailer, yes. Generally the max inflated pressure printed on the sidewall is also the recommended pressure. But check placards and tires to be sure they match.

Truck, no... or probably not necessary anyway. You CAN max out the tire pressure and nothing bad will happen, it'll just be a rough ride. The way to know what your truck tires recommend is on the data sticker in your driver's doorjamb or glovebox, and will require you to know the axle weights with your trailer hitched and loaded. Pretty easy to figure by having your loaded rig weighed at a truck scale, commonly available at truck stops (for a fee), grain elevators or asphalt plants (sometimes free, call ahead and ask). Here's my thread from last year of how I figured out the best tire pressures to use (on my tow vehicle) to smooth out my ride.