Trailer tire Pressure

[Larry&Donna-AK]

Unfamiliar territory for me ... isn't initial recommended inflation pressures based on "Cold" inflation pressures?

[Star Dreamer]

The correct tire inflation pressure for your trailer tires was set by the trailer manufacturer and displayed on the trailer’s certification label, tire placard and in the owner manual. The recommended pressures found there provides the load capacity from the OE tires to satisfy what the vehicle manufacturer deemed appropriate for the Original Equipment tires.

 

...

Unfortunately this is not always true.

 

Example see picture below. Trailer came with Load Range D "ST" tires. At 65 PSI the maximum rated load per tire is only 2540# x 2 = 5080 but the placard shows rating is 5200# per axle. In this case what the manufacturer recommends doesn't work, and even worse doesn't even indicate that you should be using "ST" tires. It has gotten to the point that you cannot trust the vehicle (trailer) manufacturer, especially where tires are concerned.

 

 

We have had to go with Load Range E tires rated at 2830# at 80 psi to meet/exceed the axle ratings.

Dave

[HERO Maker]

I'm with Dave on this one. Never trust what the trailer manufacturer is stating for tire inflation or weight load. They (not all) have been installing the lowest price options that can get close to what they want to claim for sales purposes.

Don't exceed the axle weight rating simply because you now have better tires. You're better off than before, but don't push it.

Of course then there is what the frame can handle!

[rickeieio]

It's not just trailers. My last pickup had a door sticker that recommended 36 psi. Tires were rated for 45 psi. A trip across the scales showed max pressure was needed with just a cross box and myself in the truck. Granted, I'm not a small unit, but c'mon, it's advertised as a truck, not a sedan.

 

FWIW, I have a motorcycle that the manufacturer recommends about 10 psi less in the front than the tire mfgr specs. The difference in handling is pretty significant.

[Ronbo]

I have the Goodyear tires on my trailer. I run them at 125psi per the wheel weight. The first couple of times my rpms shoes 148 - 155 going down the road I was sceptical. Now I don't worry about it. Been running them this way for a while now.

[TireHobby]

Unfortunately this is not always true.

 

Example see picture below. Trailer came with Load Range D "ST" tires. At 65 PSI the maximum rated load per tire is only 2540# x 2 = 5080 but the placard shows rating is 5200# per axle. In this case what the manufacturer recommends doesn't work, and even worse doesn't even indicate that you should be using "ST" tires. It has gotten to the point that you cannot trust the vehicle (trailer) manufacturer, especially where tires are concerned.

 

 

We have had to go with Load Range E tires rated at 2830# at 80 psi to meet/exceed the axle ratings.

Dave

Unfortunately you have used an outdated certification label. The rules changed in 2007. But, it does not exempt the vehicle manufacturer from making the errors. The two glaring errors are the tire size and the axles not being derated to 5080# GAWR. The owner of that trailer should inform NHTSA and provide them with that picture. It’s a safety violation that can be quickly fixed with a corrected certification label. A recall may be initiated if that isn’t an isolated incident.

 

In the eyes of the industry the vehicle manufacturer is solely responsible for setting the correct tire pressures for the Original Equipment tires. The correct tire pressure is reflected in the cold recommendation found on the tire placard/certification label and in the owner's manual. The tire industry WILL NOT dispute NHTSA on that.

[Star Dreamer]

Unfortunately you have used an outdated certification label. The rules changed in 2007. But, it does not exempt the vehicle manufacturer from making the errors. The two glaring errors are the tire size and the axles not being derated to 5080# GAWR. The owner of that trailer should inform NHTSA and provide them with that picture. It’s a safety violation that can be quickly fixed with a corrected certification label. A recall may be initiated if that isn’t an isolated incident.

 

Tirehobby, I don't want to side track Broncohauler's post too much but we are talking about trailer tire pressures here. the label is the one that the trailer manufacturer put on not us, it is not outdated for the trailer as the trailer is a 2005 unit and 2007 labels would not have been available yet. Since we are the owners I thought about contacting them but I would be worried that they would do just that, de-rate the axles to 5080# in lieu of changing the tire size and pressure to match a load range E tire. We are already close to maxing out one of the axles at 5200# and cannot move weight around to lighten it. I guess we could always try to contact them and see what they say.

[TireHobby]

Tirehobby, I don't want to side track Broncohauler's post too much but we are talking about trailer tire pressures here. Since we are the owners I thought about contacting them but I would be worried that they would do just that, de-rate the axles to 5080# in lieu of changing the tire size and pressure to match a load range E tire. We are already close to maxing out one of the axles at 5200# and cannot move weight around to lighten it. I guess we could always try to contact them and see what they say.

There isn't much the trailer manufacturer can do to correct their error. The most common thing they do when a placard has that type of error is lower the GAWR and cargo capacity to be within GVWR. They have built it to a GVWR and other modifications to get it into specifications would be difficult to accomplish on a single model. Think about it. If all other owners found that a modification was in the wind they would also want it.

 

On the other hand if the specs are valid with the 5200# axles and only the tire size/inflation is in error the manufacturer could provide a new certification label with 5200# axles and a tire upgrade to the next load range that would support the 5200# axles. Free new tires/rims would solve the problem.

[rynosback]

Rynosback,

I spoke to Goodyear several years ago about a different issue but had been using their charts for inflation (I have 17.5 inch G114s). I was noticing about a 16% increase in pressure (100 psi to 116 psi) as my tires heated up at highway speeds (for me 62mph). Temps stayed good. All of their literature and other references on the web said that increase should be only 3 - 5% ( 3 - 5 psi). The first few folks I spoke with stumbled and bumbled when I asked about proper inflation pressures and then this increase. When pressed they finally connected me to an engineer at their testing facility. He said the 3 - 5% was not accurate and what I was seeing was normal on larger, heavier tires. He also advised me to use the inflation charts for my weights as he had helped develop these at their facility. Moral to the story: you're going to get multiple answers from the manufacturer and you have to choose which info to take. I went with the engineer.

I would agree with you that the engineer is the person that I want to follow there advice. I honestly never had check the pressure when hot. I will check it to see if I get the same results as you did. I also have the G114's. Thanks for the feedback.

[jadatis]

I know we discussed this before but not finding it in the resource guide

What do you guys recommend for tire pressure?

17.5 tires Sailun S637. 215/75R17.5 Max load rating 4805at 125psi

3axles

About 19,000 lbs loaded

Tires max 125 psi I run them around 115psi and I'm finding everything jostled around in the trailer pretty heavily where I did not with the 15 inch tires.

 

Filled your tires in in spreadsheet I made , to give a range in pressure in wich your tires are save and no bumping.

Asumed you yudged your total weight of 19000 to low so made it 20000 of wich minimum to law of 10% pinload.

This gives 18000 lbs on the 6 tires, and assumed R/L loaddivision of 47.5/52.5% per axle, and also 5% difference between lowest and highest axle.

This gives lowest asumed weight on one wheel of 2707.5 lbs and highest asumed wheight on one wheel 3307,5 lbs .

So build in as much possible reserve wich in practice often happens.

 

Then I made picture of it and read it like this.

At 95 psi all around, the lightest wheel will to my conclusions give yust no bumping ( green at bumping border).

AT 85 psi the heavyest asumed load on one wheel will give yust no damage by overheating when driving up to 75m/h ( red at 120km/75m/h

At 80 psi heavyest no damage when max speed 65 m/h

 

So if you keep your cold pressure ( inside tire temp = outside tire temp= about 65 to 70 degr F.) between those values your save and no bumping.

Plan then is to keep it filled to 95 psi , but if you measure in time cold 80 psi and you are not able to fill up at that moment, you dont have to be affaid your tires will damage, if you drive not faster then 65m/h.

Also assumed maximum speed of your tires to be 75m/h ( speedcode L) because I could not find that , but these larger tiress often dont go higher, but try to find that. If Max speed of tire is higher , lower pressure is able without damage, filled in 140km/87m/h as max speed of tire and it only gave 5 psi lower pressure for all , so 90/80/75 psi.

 

Here the picture , see if you can work it out.

 

[SuiteSuccess]

TireHobby,

 

I'm a little confused. I read your reference, so are you recommending inflating to placard cold inflation pressures for the tire size no matter what the individual wheel weight because that is what the trailer manufacturer says to do? That seems counterintuitive to what the tire manufacturers recommend which is based on actual weight the tire is carrying.

[Alie&Jim's Carrilite]

I go with what the tire manufacturer says. Which is also what most of the forum members do as well.

[rynosback]

I go with what the tire manufacturer says. Which is also what most of the forum members do as well.

Well the engineer from the tire manufacturer atleast.

[TireHobby]

TireHobby,

 

I'm a little confused. I read your reference, so are you recommending inflating to placard cold inflation pressures for the tire size no matter what the individual wheel weight because that is what the trailer manufacturer says to do? That seems counterintuitive to what the tire manufacturers recommend which is based on actual weight the tire is carrying.

The correct tire pressure for OE tires is what has been recommended by the vehicle manufacturer. The correct tire pressure for replacement tires that do not use the same load inflation chart as the OE tires is the amount of inflation pressure that brings the replacement tires up to the load carrying capacity provided by the OE tires.

 

Example: The recommended inflation pressure for OE tires is 80 psi (ea. tire) and it provides 3420# of load capacity. The target load capacity for the replacement tires is 3420#. The replacement tires must be capable of providing 3420# of load capacity with what ever inflation pressure is needed to do so.

[TireHobby]

Tire engineers are very knowledgeable about tire mechanics. They are sometimes lacking in the regulations governing tires on our highways and the regulations vehicle manufacturers must abide. Even industry standards are often misinterpreted by the engineers. For instance: Most RV trailer manufacturers will use tire fitments that are within the guidelines of the building instructions but are close to being maxed out when it comes to individual tire load capacity. Therefore the vehicle manufacturer will use recommended tire inflation pressures for the maximum load capacity of the tire. The situation is compounded by manufacturers of Special Trailer (ST) tires saying it's ok to run their tires at max operating pressures at all times. What the owner faces is tires with no wiggle room for adjustments. All ST tires can have their maximum inflation pressures increased by 10 psi but it doesn't effect load capacity, just speed. Goodyear is the only manufacturer that approves that adjustment but I've never came across a vehicle manufacturer that will recommend it.

 

I don't provide things that so-in-so does or what I do unless it's within the regulations and industry standards.

 

I live just 10 miles from Michelin of North America. On the one hand they will tell people to weigh their RV and air the tires evenly across each individual axle. What they leave out is the minimum starting point, the vehicle manufacturers recommended inflation pressures. When you get into Michelin's manuals and data books you will find that they say replacement tires MUST provide, at the minimum, the same load capacity as the OE tires. That's by inflation folks and it follows industry standards.

[oletimer]

I installed 17 1/2" Goodyear (G114) on my 36'(36' 11") Teton with Mor/Ryd IS about 5,000 miles ago, and thought that made my ride a little ruff, and bouncy. A few days ago, I picked up our new Spacecraft (37') with 8K air ride axels, and thought with the air ride I would get a much better ride. I have only pulled about 700 miles so far, and after the first 300, Wyatt at SpaceCraft, softened the bladders a few pounds, but not sure it has helped. I'm not sure the ride is too hard, or I getting a bucking in the pull? Everything is level, I never got that buck with the Teton, so I want to lower my tire pressure and try that. My total 5er weight loaded, is 22,840#, with 6,120# tongue weight 26.8%. In the old days, I always shot for 25%, but I can't believe 1.8% over would cause a problem. 16,720# triple axel = 2,787# per tire. I had the pressure set at 100# cold at 55*F. A couple of the tires jumped to 116#, with out the temp going above 62*. This is one of the times that the more I read, the more confused I get. I'm at a park WiFi overnight only, but if anyone has any thoughts, I will check back in a day or two. Just came down from St. Louis on I-70/I-64/I-24 to Paducah with rain, wind, hail, and some twist, so the tire problem wasn't the only concern. Thanks for any feed back. MERRY CHRISTMAS!!!! Dick T

[HERO Maker]

Dick, according the the Goodyear Inflation Chart, 100 #s of pressure is for a weight of 4,020 lbs. So yes, your tires appear to be over inflated. But the lowest air pressure they list for that tire is 90#s at 3,695 lbs. Anything with lower weight is not even on the chart.

I would get your rig weighed for individual wheel weight soon so you can know exactly where you need to be on each tire.

 

I'm sure others will chime in with more knowledge on the best minimal tire pressure to use on that setup.

 

Which air suspension system do you have?

[oletimer]

Rocky,

Thanks for the info. Just made it to Wauchula, Florida, and the coop park (SKP Resort), so have some WiFi. We have the Ridewell/Featheride system. Left Concordia on Wensday the 23rd, made it to Paducah, Ky. after driving through 50-60 PH winds, rain, hail, with some twist, and made home for the night in a RV park with ankle deep water for the night. Drove all day on the 24th with much the same conditions and thought we would quit early. Then after entering Georgia, I saw a sign with arrow that said "Fort Mountain State Park", made the turn only to find it was 27 miles east of I-24, Oh well at least got out of all the traffic. First of all, I thought most folks, except us of coarse, would be home with their family, WRONG. Then "what was I thinkin'", Fort MOUNTIAN was in fact on a mountain, but as we were now in a flood warning, I thought maybe that might be the place to be, again wrong. Took so long to get there, it was dark. Had to lock in the power dividers, because the front wheels was sliding when I was trying to get parked, but after 2 hours from I-24 in the dark, and rain we were dry, and safe, but tired. Still thankful as we celebrated the Birth of our Lord. Spent the night in North Florida at The Suwannee River State Park, long enough to "skin" the brand new Space Craft (another story). Got here today, the 26th, and having some problems with the kitchen slide (worm gear broke), but after seeing all the accidents, and watching all the idiots driving like there was no tomorrow, which was true for some, we are still very thankful. How's that for a LONG ANSWER??? Dick T

 

 

BTW, I will get the weight on each tire, because the two front curbside tires raise much quicker than the others. They all level out at about the same though.

90# cold up to 115#, and heat never more than 10-15 degrees above ambient.