Greystone Tire Inflation Pressure Discussion

[jheitman]

Most everyone will tell you to inflate your trailer tires to the full pressure listed on the trailer placard. This pressure is associated with the full load capacity of the tire. My Greystone uses Power King ST235/80R16 tires, load rating E, supporting 3520 lbs at 80 psi. Fully loaded, my four trailer tires carry 9060 lbs, without any fluids in the tanks, or around 2300 lbs each.

My question is why don't we follow the Load/Inflation tables for the tires on our trailers? According the the tables, pretty much identical for all brands for a specific size, I should be inflating to 40 psi, for my load. If I added full tanks, 1400 lbs split equally between the axels and the king pin, my tire load would be 2475 each and 50 psi would cover this loading with margin.
ST tires are only rated for up to 65 mph, and Goodyear recommends adding another 10 psi beyond the recommended pressure for your load for higher speeds. Including this precaution, I should inflate to 60 psi.

80 psi seems like a case of definite over inflation in my case, leading to reduced tire contact patch for traction and increased wear on the center of the tread. I'm really happy that Heartland has used a tire with so much margin, although some may be required for tires made in China. There is no doubt that tire problems can happen when under inflated, so we want to find the right pressure to avoid being under inflated without blindly over inflating.

I called GM and asked about truck tire inflation. They said they recommend truck tire inflation at the pressure listed on the door label when pulling a trailer, and I agree based upon the load inflation table for my tire, near full load. They said I should use the manufacturer load inflation tables if not pulling a trailer. My truck uses the same tire on all four wheels. GM recommends 50 psi in the front and 80 psi in the rear. These pressures align nicely with the load inflation tables for typical truck wheel loads.

I wrote to Bridgestone and they said " Unfortunately, Bridgestone/Firestone can only follow what the vehicle manufacturer wants the tires fitted onto their vehicle inflated at. All that Bridgestone/Firestone do is put a stamping on the tires' sidewall what the Max cold inflation pressure is for those tires. Remember, the vehicle recommended inflation pressure is based on other factors as well including steering, suspension and braking systems plus your vehicle's targeted design use. " Interesting!

I found some good information from Goodyear on the web.
http://www.goodyear.com/rv/pdf/marathon_gen_info_032806.pdf
Tire companies always throw in that owners should follow the pressures recommended by the trailer manufacturer, but then go one to describe inflations based upon use and loads.

"Vehicle speed, load and inflation pressures, all of which are within control of the driver, are critical factors for the safe and enjoyable operation of any vehicle" Sounds like there are choices for pressure depending on conditions, not just max pressure.

Here are the Goodyear Load Inflation tables for typical trailer and pick up tires.​

http://www.goodyear.com/rv/pdf/rv_inflation.pdf
Apparently, the Goodyear ST235/80R16 is only "D" load rated so it only goes to 65 psi.

Here is the Bridgestone site where you can download the "Bridgestone Medium & Light Truck Tire Data Book" which contains load and inflation tables for everything.
http://www.bridgestonetrucktires.com/us_eng/load/index.asp#tech_info

Seems to me that tires should be pressurized according to their expected use, speed, and load. Seems like, pressurizing to the maximum rated pressure is not always a good idea for tire life, performance and ride.

What do you think?

jim

 

[Willym]

Ideally one should inflate our tyres according to the tyre loading and add a small margin to cover load variation. However, when we weigh our rigs, we usually only get axle loads, and quite often just the tandem axle load. We do not see the individual wheel loading. Many rigs are heavier on one side, so one cannot assume that the wheel load is one quarter of the total axle load or half of the individual axle load.

There are some organizations that will weigh your wheels individually and they often appear at larger rallies. I'm not sure if they come to Heartland rallies.

 

[jheitman]

Ideally one should inflate our tyres according to the tyre loading and add a small margin to cover load variation. However, when we weigh our rigs, we usually only get axle loads, and quite often just the tandem axle load. We do not see the individual wheel loading. Many rigs are heavier on one side, so one cannot assume that the wheel load is one quarter of the total axle load or half of the individual axle load.
There are some organizations that will weigh your wheels individually and they often appear at larger rallies. I'm not sure if they come to Heartland rallies.

I've weighed my rig at a CAT Scale near here. So far, I've weighted each truck axel and both trailer axels together. I could weigh each axel individually and then weigh with one side off the scale to get the distribution from side to side per wheel. I believe that tire manufactures recommend setting all four tires at the same pressure, so I have to find the highest loaded tire and then look up the inflation from the Load/Inflation table.

I thought weighing both axels together was ok since they are very close together fore and aft, and I have two big slides, the same length, in the back. However, I also have one smaller bedroom slide on one side. So I'll try the individual wheel weighing and see what I get.

I bet that setting for the highest loaded tire, adding for possible speed higher than 65 and for full water tanks, still leads to signifiantly less than 80 psi. We'll see. I wrote to Heartland but have not received a response. I posted a reference to this posting in the Greystone "Ask the Factory" section, so we'll see if I can get a response there.

 

[Jellystone]

jheitman, I understand exactly what you are saying. It appears that you've done quite a bit of research on the tire inflation subject.--I always inflate to the MAX PSI cold before I travel with my 5th wheel. I do the same on my dually truck as well (MAX PSI cold front & rear). I use the rating stamped on the sidewall of the tire itself to get the info. I will never inflate more than the sidewall says for any reason--that rating is for the tire itself, no matter what the tire is mounted to. Proper tire selection is for the consumer to decide based on size, weight rating, intended use, load issues, durability,etc. Just remember, no matter what the vehicle manufacturer says about the tire, the tire manufacturer knows tires (and tire construction).

 

[cookie]

I think that sometime in the future we may be reading another post titled "Help Cheap Chinese Tires Exploded".
Sorry, I had to say it. Why would you want to risk blowing a tire, most blowouts are related to underinflation, when running them at the max sidewall rating will cover you.
Under inflated tires build up heat. Excess heat causes tire failure.
I'm thinking these tires will need to be replaced due to age before you wear the center out of them.
Just my thoughts.

Peace
Dave

 

[westxsrt10]

A real life moving tire traveling down the road will have higher weights placed on it compaired to setting still on a CAT scale. Depending on your tire wear you may go 5 psi under the max rating psi and still be safe.

 

[jheitman]

jheitman, I understand exactly what you are saying. It appears that you've done quite a bit of research on the tire inflation subject.--I always inflate to the MAX PSI cold before I travel with my 5th wheel. I do the same on my dually truck as well (MAX PSI cold front & rear). I use the rating stamped on the sidewall of the tire itself to get the info. I will never inflate more than the sidewall says for any reason--that rating is for the tire itself, no matter what the tire is mounted to. Proper tire selection is for the consumer to decide based on size, weight rating, intended use, load issues, durability,etc. Just remember, no matter what the vehicle manufacturer says about the tire, the tire manufacturer knows tires (and tire construction).

Hey thanks for the thoughts, thats what I'm looking for. Again, most people, not all, tell me something like "I go with what is marked on the tire" or "I go with what is marked on the RV or Truck". I'm looking for the rationale for this position. The label on the trailer is for the trailer at the trailer GVWR and the same for a truck placard on the side of the door. My trailer GVWR is 13840 lbs and the dry weight is 10185 lbs. Thats close to 2 tons of cargo allowance. This is one reason I picked Heartland, plenty of margin. We will never run the trailer anywhere near the GVWR. You can run it there, and if you do you should inflate the tires according to the label on the side, since the tires would then be at the max rated load. Where does the GVWR of 13840 come from? The GVWR is just 240 lbs under 4x3520 lbs, the max load rating of the tires, so again, if you load the trailer so your at the GVWR then the tires should be at their max load rating and so the tire pressure should be 80 psi.

Trucks with fifth wheels turn out close to or sometimes over their GVWR, so using the truck recommendation on the door or in the owners manual makes sense.

For example, the actual marking on my Bridgestone truck tires is "MAX LOAD SINGLE (3042 LBS) AT (80 PSI) MAX PRESS". I think this means just what it literally says. The maximum load for the tire is 3042 lbs and the tire should have 80 psi maximum pressure at that load. It does not say to fill the tire to 80 psi no matter what. Again, GM told me to follow the Load/Inflation table for my rear tires if not pulling a trailer. They nominally recommend less than the max pressure labeled on the tire for the front tires; the pressure taken from the Load/Inflation table for the max load for the front end axel.

I know what I'm throwing out is exactly counter to conventional wisdom and will not make sense to lots of people, but I'm trying to find out why. Why do people follow the rating on the tire in every case? It is not my intension to critize the experience of anyone, but I am trying to find out if there is some technical basis for the common position or is the conventional wisdom too conservative. There is no doubt that under inflation kills tires, but they can be way down in pressure before one even notices they look a bit down. What would happen if I ran my trailer tires at 60-65 lbs, is that underinflated? The literature says no.

I'm obviously perplexed by this contradiction between years of RV experience and technical recommendations from the tire manufacturer based upon a lot of testing over the years. I want to run my trailer at the best pressure for the actual conditions. Does that clarify my position any better?

 

[jheitman]

I think that sometime in the future we may be reading another post titled "Help Cheap Chinese Tires Exploded".
Sorry, I had to say it. Why would you want to risk blowing a tire, most blowouts are related to underinflation, when running them at the max sidewall rating will cover you.
Under inflated tires build up heat. Excess heat causes tire failure.
I'm thinking these tires will need to be replaced due to age before you wear the center out of them.
Just my thoughts.

Peace
Dave

Dave:

The reliability of Power King tires has not been figured into my discussion and I don't know how. Maybe running at maximum pressure actually hurts the tire, who knows. We need a tire expert to jump in here... I've read all views from they blow up and get them off as soon as possible to they run fine for years, no problems. I've read that some people have trouble with tires we normally don't associate with China, like Goodyears. So jumping to another brand may not be the solution. I'm suggesting running the tires at pressures recommended by the manufacturer, at ones actual load, may lead to the longest lifetime.
I hope I don't have to print a retraction sometime in the near future, but I will if I'm on the wrong track.

Thanks, have a great holiday weekend,

jim

 

[jmgratz]

This is a good discussion however I failed to see anyone mention vehicle manufacturers want to have the best ride possible. A truck tire inflated to 50 psi will ride a lot softer than one inflated to 80 psi. If you go to a new car dealer and check their tires you will find almost all of their vehicle tires are under inflated to give the vehicles a softer ride during the test drives. My truck had 22 pounds in the tires when I test drove it and even after it was delivered. I had to put the required inflation in it myself.

The other point is weight from side to side on an RV is not equal. An axle might have 3200 pounds on a scale but there might be 1100 on one side and 2100 on the other side. Look at the RV and where are the heavy items such as stove, microwave, refrigerator, Television and pantry. Are they all on the same side. The when you hit a bump hard all of the weight goes down causing more stress on that tire. It is unsafe to have different inflations on the same axle from one side to the other.

I have seen during my high performance driving instructor (police) the bead on the tire roll off a rim in a fully inflated tire. If you have to make a sudden severe maneuver to avoid a collision you better have what the tire is supposed to have.

For me I will use the inflation printed on the side wall of the tire.

 

[jheitman]

A real life moving tire traveling down the road will have higher weights placed on it compaired to setting still on a CAT scale. Depending on your tire wear you may go 5 psi under the max rating psi and still be safe.

Westxsrt10:

Good point. I was wondering if I should allocate some additional load (and necessary pressure) for when the trialer bounces and hits the bottom of the movement, causing increased load on the tires. However, seems like that effect would be accounted for if you are running maximum load and maximum pressure, so wouldn't it be accounted for when runing 80% load at the associated pressure from the Load/Inflation tables, for the specific tire in question?

Thanks, and have a great holiday weekend

jim

 

[lwmcguir]

Dave:

The reliability of Power King tires has not been figured into my discussion and I don't know how. Maybe running at maximum pressure actually hurts the tire, who knows. We need a tire expert to jump in here... I've read all views from they blow up and get them off as soon as possible to they run fine for years, no problems. I've read that some people have trouble with tires we normally don't associate with China, like Goodyears. So jumping to another brand may not be the solution. I'm suggesting running the tires at pressures recommended by the manufacturer, at ones actual load, may lead to the longest lifetime.
I hope I don't have to print a retraction sometime in the near future, but I will if I'm on the wrong track.

Thanks, have a great holiday weekend,

jim

There is only one correct inflation if you are 75% loaded or more based on the tire rating. That is to inflate to the maximum inflation (cold) listed on the sidewall.

 

[jheitman]

This is a good discussion however I failed to see anyone mention vehicle manufacturers want to have the best ride possible. A truck tire inflated to 50 psi will ride a lot softer than one inflated to 80 psi. If you go to a new car dealer and check their tires you will find almost all of their vehicle tires are under inflated to give the vehicles a softer ride during the test drives. My truck had 22 pounds in the tires when I test drove it and even after it was delivered. I had to put the required inflation in it myself.

The other point is weight from side to side on an RV is not equal. An axle might have 3200 pounds on a scale but there might be 1100 on one side and 2100 on the other side. Look at the RV and where are the heavy items such as stove, microwave, refrigerator, Television and pantry. Are they all on the same side. The when you hit a bump hard all of the weight goes down causing more stress on that tire. It is unsafe to have different inflations on the same axle from one side to the other.

I have seen during my high performance driving instructor (police) the bead on the tire roll off a rim in a fully inflated tire. If you have to make a sudden severe maneuver to avoid a collision you better have what the tire is supposed to have.

For me I will use the inflation printed on the side wall of the tire.

Jim:

Excellent points. I will definately re-weigh my rig and find out how much each axels is loaded, should be interesting. I didn't think the difference could be as large as your example numbers, but we'll see. All the heavy stuff is on one side. This may be the explaination. However the trailer tire pressure is suggested for max weight, GVWR.

I too believe we should be inflating to the pressure that we are "supposed to". The question is what is that pressure? My tires are marked for pressure at maximum load. The Load/Inflation tables tell you what pressure to use at other loads....

Again, GM, usually ultra conservative, recommended to me to follow the tables when not at maximum load, or without a trailer...

Have a great weekend and thanks for taking the time to help me see all the aspects of the issue. I really appreciate it guys.

jim

 

[lwmcguir]

Most everyone will tell you to inflate your trailer tires to the full pressure listed on the trailer placard. This pressure is associated with the full load capacity of the tire. My Greystone uses Power King ST235/80R16 tires, load rating E, supporting 3520 lbs at 80 psi. Fully loaded, my four trailer tires carry 9060 lbs, without any fluids in the tanks, or around 2300 lbs each.

My question is why don't we follow the Load/Inflation tables for the tires on our trailers? According the the tables, pretty much identical for all brands for a specific size, I should be inflating to 40 psi, for my load. If I added full tanks, 1400 lbs split equally between the axels and the king pin, my tire load would be 2475 each and 50 psi would cover this loading with margin.
ST tires are only rated for up to 65 mph, and Goodyear recommends adding another 10 psi beyond the recommended pressure for your load for higher speeds. Including this precaution, I should inflate to 60 psi.

80 psi seems like a case of definite over inflation in my case, leading to reduced tire contact patch for traction and increased wear on the center of the tread. I'm really happy that Heartland has used a tire with so much margin, although some may be required for tires made in China. There is no doubt that tire problems can happen when under inflated, so we want to find the right pressure to avoid being under inflated without blindly over inflating.

I called GM and asked about truck tire inflation. They said they recommend truck tire inflation at the pressure listed on the door label when pulling a trailer, and I agree based upon the load inflation table for my tire, near full load. They said I should use the manufacturer load inflation tables if not pulling a trailer. My truck uses the same tire on all four wheels. GM recommends 50 psi in the front and 80 psi in the rear. These pressures align nicely with the load inflation tables for typical truck wheel loads.

I wrote to Bridgestone and they said " Unfortunately, Bridgestone/Firestone can only follow what the vehicle manufacturer wants the tires fitted onto their vehicle inflated at. All that Bridgestone/Firestone do is put a stamping on the tires' sidewall what the Max cold inflation pressure is for those tires. Remember, the vehicle recommended inflation pressure is based on other factors as well including steering, suspension and braking systems plus your vehicle's targeted design use. " Interesting!

I found some good information from Goodyear on the web.
http://www.goodyear.com/rv/pdf/marathon_gen_info_032806.pdf
Tire companies always throw in that owners should follow the pressures recommended by the trailer manufacturer, but then go one to describe inflations based upon use and loads.

"Vehicle speed, load and inflation pressures, all of which are within control of the driver, are critical factors for the safe and enjoyable operation of any vehicle" Sounds like there are choices for pressure depending on conditions, not just max pressure.

Here are the Goodyear Load Inflation tables for typical trailer and pick up tires.​

http://www.goodyear.com/rv/pdf/rv_inflation.pdf
Apparently, the Goodyear ST235/80R16 is only "D" load rated so it only goes to 65 psi.

Here is the Bridgestone site where you can download the "Bridgestone Medium & Light Truck Tire Data Book" which contains load and inflation tables for everything.
http://www.bridgestonetrucktires.com/us_eng/load/index.asp#tech_info

Seems to me that tires should be pressurized according to their expected use, speed, and load. Seems like, pressurizing to the maximum rated pressure is not always a good idea for tire life, performance and ride.

What do you think?

jim

You are going to be right 95% of the time for trailers if you just inflate it to the rated pressure on the sidewall. You guys are making this way to complicated. We haul a lot of livestock, hay, rock, and so on. Do you think we get out and let the air out of the tires when we are running empty 1/2 the time? Same was for over the road trucks. The don't always have a back haul. The run the rated pressure 100% of the time. If you go to a tire that is greatly overrated such as putting 17.5 inch wheels tires then that is the time to worry about how much air you should put in.

 

[caissiel]

Ever since radial tires have been installed on my cars and trucks I have inflated them to the side wall pressure reading.
I had cheap tires on a new car that I had inflated to 35PSI and replaced them with michelin tires that they inflated to 26 PSI, and I could not feel the difference, so I just inflated them to 35PSI. I have never had a broken belt or damaged tires, and I buy tires on price.

I you underinflate the tire you can only get in trouble, and like GY says you can run with 10% overinflation in order to prevent heating at high speed. So to me they tell you yhat tire failures happen at underinflation and heat.

The ecomodders, the forum that discuses fuel economy, suggest that tires should be inflated to 10% overinflation. To me its plain simple, don't gamble on tire pressure and go with what is best.

I just installed 4 new Michelin tires on my Cabriolet because I got a great deal. The owner of the tire store asked me the other day how my car drove, you most feel the difference. Well I told him there was no way I can feel the difference on the roads that we have to ride on. I replaced 4 Chinese tires with these Michelins.

I would not worry about the wear on the middle of a trailer tire, I have never replaced a tire due to center baldness, but I did change many due to steel belts showing on the sides, and that includes car and truck tires.

As for my experience, for years I have done better then 50K miles per years on tires that are inflated to the limit and tires purchased on price.

 

[jheitman]

This is a good discussion however I failed to see anyone mention vehicle manufacturers want to have the best ride possible. A truck tire inflated to 50 psi will ride a lot softer than one inflated to 80 psi. If you go to a new car dealer and check their tires you will find almost all of their vehicle tires are under inflated to give the vehicles a softer ride during the test drives. My truck had 22 pounds in the tires when I test drove it and even after it was delivered. I had to put the required inflation in it myself.

The other point is weight from side to side on an RV is not equal. An axle might have 3200 pounds on a scale but there might be 1100 on one side and 2100 on the other side. Look at the RV and where are the heavy items such as stove, microwave, refrigerator, Television and pantry. Are they all on the same side. The when you hit a bump hard all of the weight goes down causing more stress on that tire. It is unsafe to have different inflations on the same axle from one side to the other.

I have seen during my high performance driving instructor (police) the bead on the tire roll off a rim in a fully inflated tire. If you have to make a sudden severe maneuver to avoid a collision you better have what the tire is supposed to have.

For me I will use the inflation printed on the side wall of the tire.

JMGRATZ:

One other comment.

Another consideration for wondering if lower pressure is best is to improve the ride of the trailer. What's wrong with having a softer ride as long as the tire is riding as designed. I want the trailer to have the softest ride possible without sacraficing any safety issues, and that can only improve with lowering the tire pressure a little. I'm considering adding a 5th Airborne pin box to improve things and I thought a softer ride for the trailer has to help.

Anyway I don't think there is anything wrong with having a soft ride, as long as the tire pressure is above that listed in the load/inflation table.

Here is a copy of the Goodyear tables for RV truck tires, just as an example. Click the little picture and it will expand:

 

[jheitman]

You are going to be right 95% of the time for trailers if you just inflate it to the rated pressure on the sidewall. You guys are making this way to complicated. We haul a lot of livestock, hay, rock, and so on. Do you think we get out and let the air out of the tires when we are running empty 1/2 the time? Same was for over the road trucks. The don't always have a back haul. The run the rated pressure 100% of the time. If you go to a tire that is greatly overrated such as putting 17.5 inch wheels tires then that is the time to worry about how much air you should put in.

LWMCGUIR:

I hear you. However, I think the 5th wheel trailer tire load can be measured and it won't change much from day to day, except for minor variations in stored food. So an RV trailer is not really like an over the road truck trailer where some times the truck is fully loaded to the max and sometimes its only half loaded. So, I thought one could come up with a pressure and then hold that all the time, and wouldn't have to adjust it at all. I thought of measuring the weight and then inflating to the next load up in the table just to make sure we are never under-inflated. Does this make sense? Again the Load/Inflation tables tell you what pressure to use for each load level on the tire so the tire is riding as designed. More load makes the tire side wall bulge some and so you increase pressure to get back to the proper tire shape. The table gives the pressure that is optimum for every load. Max pressure is only optimum for max load, I think. GM agreed with this position for their vehicles and I'm still waiting to hear from Heartland, Goodyear, Power King and the National Tire and Rim Association.

Thanks again,

jim

 

[TXBobcat]

I have a question on this subject. If you take and inflate your tires to a recommended rate for the weight on that tire when you are sitting on a level concrete camp site, what happens to the weight on the tires when you get it out on the highway? None of our highways are made flat, they are crowned for water to flow away from the road. If you are in the left hand lane, many times your trailer is leaning less than if your in the right lane where water is made to run into the curb. You now have much more weight on the curb side than on the median side. When you go around a curve at 60 mph the weight changes on your tires.

The weight on your tires changes all the time when you are traveling on our city roads and state highways. If you get so critical about the exact inflation of your tires, in my mind, you are working your self to death.

I check my tires with my Pressure Pro system before I leave. If the tires are within a pound or two I don't mess with them and I carry my tires at the max tire pressure shown on the side walls. If you weigh your trailer every week you will get a different weight each time. This is because you change how much groceries your carrying, how much, if any, water in your tanks (my main tank is the fresh water tank) and other things that change in your trailer.

I don't think that you have to go around each morning and add a pound or remove a pound or two of air. There are so many variants and changes that happen from day to day and while your traveling down the road you would be in trouble if that were the case. I do believe it is better to have a tire over inflated than under inflated.

FWIW
BC

 

[jcarnevale]

jheitman,

I personally think you are on the right track. I pull my trailer well below the max weight and I see it bouncing around in the mirror and always find my rear TV wires disconnected from the harsh ride. I don't drive my truck around town empty with 80 psi in the rear tires, I lower them to 65 psi. Why wouldn't I do that for the trailer also?

PS: Very irenic post, keep up the good work!

Jay

 

[jheitman]

I have a question on this subject. If you take and inflate your tires to a recommended rate for the weight on that tire when you are sitting on a level concrete camp site, what happens to the weight on the tires when you get it out on the highway? None of our highways are made flat, they are crowned for water to flow away from the road. If you are in the left hand lane, many times your trailer is leaning less than if your in the right lane where water is made to run into the curb. You now have much more weight on the curb side than on the median side. When you go around a curve at 60 mph the weight changes on your tires.

The weight on your tires changes all the time when you are traveling on our city roads and state highways. If you get so critical about the exact inflation of your tires, in my mind, you are working your self to death.

I check my tires with my Pressure Pro system before I leave. If the tires are within a pound or two I don't mess with them and I carry my tires at the max tire pressure shown on the side walls. If you weigh your trailer every week you will get a different weight each time. This is because you change how much groceries your carrying, how much, if any, water in your tanks (my main tank is the fresh water tank) and other things that change in your trailer.

I don't think that you have to go around each morning and add a pound or remove a pound or two of air. There are so many variants and changes that happen from day to day and while your traveling down the road you would be in trouble if that were the case. I do believe it is better to have a tire over inflated than under inflated.

FWIW
BC

Excellent points. I'm learning with each posting.

I'm not suggesting adjusting the pressure each day. I'm suggesting weighing your rig once, figuring out a tire inflation and holding that value unless something extreme changes with the loads in your rig.

I would weigh the trailer tires for a typical travel configuration, full propane, no water in tanks, clothes, personal effects, etc. I would add one quarter of half the full tank weight to each tire, an approximation assuming the other half goes to the pin. In my case all tanks are forward of the axels. I would take the highest load of the four tires and I would look up the closest load over my number in the tire table and then move up to the next higher load to cover any future variations or changes caused by roadway surfaces, or whatever. I would then add 10 psi to cover me in case I choose to go over the 65 mph speed rating going down a steep hill with a corresponding steep rise coming up. This pressure is what I would maintain cold by monitoring once each week.

This is a little complicated because of the initial weighing, but not complicated at all thereafter. What do you all think?

Here is a Michelin publication for RVs that talks directly about doing what I described.
http://www.michelinrvtires.com/michelinrv/tires-retreads/load-inflation-tables.jsp

If you don't weigh your trailer, use the max pressure in the placard. If you can measure your trailer tire loads, use the pressure calculated from the load table for your tire. That's my story for now, awaiting further postings from you guys. I'm the novice, armed with techical information from tire manufactures and you guys are the veterans of the school of hard knocks dealing with RVs over the years. Please keep commenting...

Respectfully,

jim

 

[cookie]

Jim, you are making rocket science out of putting air in a tire.
Run the max sidewall pressure listing.
JMHO.

Peace
Dave