Tire pressure

[fjr vfr]

My trailer lists pressure at 65 psi for the 225/75-15 load range D tires that come with the trailer.
These tires were replaced with load range E tires of the same size. Load range E tires are rated to run at 80 psi
I weighed my trailer and have just under 8,000 lbs on the axles and 1,800 lbs pin weight.
Looking at Maxxis load and inflation tables they show 45 psi at 2,020 lbs per tire.
I don't plan on running below the 65 psi listed for the original tires, I think 45 psi is too low, but I am now running a stiffer tire, so should I be running at a higher psi than 65? I think 80 psi would be too hard for the weight.


I know many people go to a higher load range tires, so I wonder about other opinions?


Thanks

[sourdough]

I went from the same tire you had to the same E rated tires. My trailer is 10k gvw and runs about 9200 or so. I run my trailer tires at 80 psi and completely disregard the "tongue/pin weight". That is an ideal number but when you are driving down the road hitting frost heaves, pot holes, dips, jumps....each of those tires isn't carrying the "ideal" load. In many, if not most, they are way overloaded in some of those scenarios. As far as rougher ride, I've never seen it. Since going to the E tires vs the D tires my trailer actually rides better and nothing moves inside any longer. JMO/YMMV

[Wing-in-it]

I always run 80 psi. Low tire pressure creates heat.... Heat is bad.

JMHO.....

[notanlines]

It would be my opinion at the tires should run at 80 PSI like Danny suggested. I can't back that up with manufacturers informational data, but when you went up from a D to an E I believe the best scenario is 80 PSI.

[JRTJH]

225 80R15 LRD tires at 65PSI are rated to carry 2540 pounds
225 80R15 LRE tires at 65PSI are also rated to carry 2540 pounds and at 80PSI are rated to carry 2830 pounds.

Why go to the expense of buying "increased load tires" and then run them at reduced pressure and lose that extra capacity. There's "nothing extra" and no "increased protection" when you run LRE tires at LRD pressures.

Sort of like going on a diet, then buying snack food to put in the refrigerator, knowing that you won't eat it and watching it go bad on the shelf while not using it.

[BrentB]

For what its worth I have the same size and brand tires as you. Three of them are load range d and one is load range e. (I had to replace 1 and LRE was all that was available.) I run all 4 at 65 psi, and the tire pressure monitoring system shows similar temperatures for all 4. If any of them were under-inflated, it would over-heat.

[flybouy]

This has been debated ad nauseum on this forum. Do a search and you will go blind with all the reading. One omission I note is what are your wheels rated for? Check that the wheels can take the increase pressure.

[ctbruce]

John sums it up best. If you pay for E's, use them as E's. Otherwise save the money and stick with D's.

[mazboy]

keep it simple. 'E' rated....80psi

[travelin texans]

keep it simple. 'E' rated....80psi

Provided the wheels are rated high enough, that would my 1st check (stamped on rear side of the wheel somewhere) before going to 80 psi.

[fjr vfr]

Provided the wheels are rated high enough, that would my 1st check (stamped on rear side of the wheel somewhere) before going to 80 psi.


From what I read the wheels are rated by weight and not pressure. I also found out while researching TPMS systems the valve stems are rated by pressure and the stems in my wheels are rated at 65 psi. I've made an appointment to replace them with the proper stems.


Most all the responses are what I expected. Since they would be stiffer than D rated tires, I would think they would flex less at 65 psi than the D rated tires do? I'm thinking Keystone planed on 65 psi to allow for higher loads on individual tires over varying conditions. Since the trailer manufactures just meet the minimum they went with D rated tires to save on cost. If they had installed E rated tires maybe they would have still listed inflation at 65 psi?

If you relate it to your car or truck they all run at something lower than the tires max rating. My truck calls for 55 psi in front and 70 psi in the rear for example. But with that said, I may just run them at 80 psi? Maybe I shouldn't overthink it? I appreciate the input. I have till after Christmas when we leave too snowbird to decide.
Thanks :)

[sourdough]

Yes, the E tires are stiffer than Ds thankfully. Think about it this way; my trailer gvw is 10k, tires were d rated at 2540 each giving me a cushion of only 40 lbs per tire over gvw at max inflation of 65 psi. I do not consider weights by removing the tongue/pin weight; sort of like the TV "max tow" rating...pretty much meaningless to me since 1) the tongue/pin is going to vary and 2) 1/2 the time you are on the highway that weight is being transferred to the trailer/trailer tires so the "ideal" weight that the manufacturer straps you with is just idealistic IMO.

Your trailer is apparently running considerably heavier than mine and I wouldn't for one second think I could bet by on a D rated tire - especially after seeing the damage they can do in about 10 seconds when they disintegrate.

Do the E rated tires flex less than the D? I think so. Is that bad? No, not at all. In fact, it is probably a good thing. Yes, the manufacturers give you the VERY minimum to get by the LOWEST possible rating they can come up with, which, in real life is generally well below what you should have and in many dangerous IMO (as in my case).

Some wheels have the psi stamped on them, some the weight. The psi will correspond to the weight for whatever weight rating the max tire has. Mine was stamped with the weight, we put in new valve stems when the tires were installed.

Yes, you should run the new E rated tires at 80psi if the wheel allows; I would not do anything less, especially at your weight. And yes, you are overthinking it. Just get the E tires, inflate them to 80psi and get some peace of mind....beats the heck out of sitting on the side of the road with a tire carcass wrapped around your axle, your wheel well torn up, gas lines cut into and underbelly all cut up....in the middle of nowhere. And, btw, the inflation pressures recommended on my truck are 80 psi rear (max inflation) and 65 front. Don't overthink it....let logic, and safety, be your guide.

[Ken / Claudia]

Tires are different for the RV vs tow vehicle or passenger car. I adjust the psi in the rear truck tires depending on the load. Some do that, nowdays with the factory TPMS some do not adjust them. RV tires stay at the max psi the tire has printed on them.
Regarding the rv tires, I changed brands and from d to e and from 65 to 80 psi. No noticed change in bounce or tracking/towing. Maybe if you rode in the RV you might find differences. For me it is just a added safety factor. As others have mentioned.
I firmly believe the RV tires get a lot more abuse then many realize and unless your reading through the RV forms about tires many do not inspect or check them as they need. Tires/wheels/bearing real important and not given the same inspection as many other parts of the RV especially for the new RVer.

[fjr vfr]

Great input. BTW, my trailer's gross is 10,600 lbs. When I put it on the CAT scale the trailer axles weighed 7,380 and my pin weight at 1,780. total trailer weight 9,160 lbs.

Those numbers will go up slightly for our snowbird trip, as we'll be adding a few more things we don't take on shorter trips.
I was considering splitting the difference to 72 psi, but all the input is swaying me towards 80 psi. I guess I can't go wrong with that decision.


Thanks :)

[CWtheMan]

Great input. BTW, my trailer's gross is 10,600 lbs. When I put it on the CAT scale the trailer axles weighed 7,380 and my pin weight at 1,780. total trailer weight 9,160 lbs.

Those numbers will go up slightly for our snowbird trip, as we'll be adding a few more things we don't take on shorter trips.
I was considering splitting the difference to 72 psi, but all the input is swaying me towards 80 psi. I guess I can't go wrong with that decision.


Thanks :)

When an owner adds a load range (D-E) they are getting a like sized tire that provides an identical load capacity at 65 PSI. The only real difference is a few materials have been changed to allow the tire to carry more weight at higher inflation pressures. They both use the same load/inflation charts.

You're good to go :thumbsup: With a valve stem pressure rated at 80 PSI and a wheel PSI rating of 80 PSI. :applause:

[fjr vfr]

Thanks for the input.

[BadmanRick]

If the tires say 80psi on them you run 80psi. It will be a very expensive mistake to run less when the tire blows from too much heat and flexing.

[Tireman9]

You have a few different things to consider.
GAWR is not based just on the tires. All other components such as springs, shackles, brackets welded to the frame and even the strength of the frame where brackets are welded on are considered by the RV MFG. Changing one or even a couple components does not increase the strength of the other components.


As a tire engineer, I will focus on the change in tire load range and tire inflation pressure requirements.
1. It is the air pressure, not the tire that supports the load so just changing the tire load range does not increase the load capacity.
2. In Trailer application better tire life (reducing the chance of a belt separation) can be achieved with an increase in inflation up to the inflation number molded on the tire sidewall.
3. You need to confirm that no single tire has been overloaded. This means get each tire on a scale. you may need to search for a location where this can be done as not all truck scales allow this. Also get the weight with the trailer at its heaviest.


More later

[rmhaney]

Make sure you check the rims. My new Sprinter came with China Bombs load range D. I checked the back of the rims and they were stamped for load range E so I up graded to E. Tires are designed to run at a specific pressure and will have normal wear using that pressure. Anything less or more will give you uneven wear patterns and may cause the tire to run hot in warmer weather resulting in premature tire failure. DO NOT put 80 PSI in it if the rimes are rated for load range D. Otherwise you could have rim failure.

[jadatis]

225 80R15 LRD tires at 65PSI are rated to carry 2540 pounds
225 80R15 LRE tires at 65PSI are also rated to carry 2540 pounds and at 80PSI are rated to carry 2830 pounds.

Why go to the expense of buying "increased load tires" and then run them at reduced pressure and lose that extra capacity. There's "nothing extra" and no "increased protection" when you run LRE tires at LRD pressures.

Sort of like going on a diet, then buying snack food to put in the refrigerator, knowing that you won't eat it and watching it go bad on the shelf while not using it.
Used the tirespecifications you gave and added 10% to the2020lbs topicstarter gave.
Then the 65psi tire would need 55psi , I calculated with the safer official European formula, ( I once got hold of, and went running with.
That they give 65 psi is general advice for trailers.
Most trailer tires are ST wich are calculated in maxload for 65mh. This gives no reserve anymore for things like unequall weight, pressure loss, etc.
Thats the reason for that standard advice of 65 psi for D-load. E- load would need 70 psi for the 2540lbs maxload of D-load.
But if you are shure of the 2020 lbs a tire as you weighed( and I added 10% to cover unequall weight R/L) , the E load would need 60 psi.

When I calculate advice for trailers, I add 10% and lower maxload, as if its a Q speedrated tire, wich is calculated in maxload for 99mh.
Then you have the highest pressure, with max reserve, with still acceptable comfort and gripp.
Comfort for a traveltrailer, is that your screws wont tremble loose from the woodconstruction.

Can do that for you, but need more information.
fi if you have ST and if weighing was fully loaded.
Number of tires and axles.

[JRTJH]

Used the tirespecifications you gave and added 10% to the2020lbs topicstarter gave.
Then the 65psi tire would need 55psi , I calculated with the safer official European formula, ( I once got hold of, and went running with.
That they give 65 psi is general advice for trailers.
Most trailer tires are ST wich are calculated in maxload for 65mh. This gives no reserve anymore for things like unequall weight, pressure loss, etc.
Thats the reason for that standard advice of 65 psi for D-load. E- load would need 70 psi for the 2540lbs maxload of D-load.
But if you are shure of the 2020 lbs a tire as you weighed( and I added 10% to cover unequall weight R/L) , the E load would need 60 psi.

When I calculate advice for trailers, I add 10% and lower maxload, as if its a Q speedrated tire, wich is calculated in maxload for 99mh.
Then you have the highest pressure, with max reserve, with still acceptable comfort and gripp.
Comfort for a traveltrailer, is that your screws wont tremble loose from the woodconstruction.

Can do that for you, but need more information.
fi if you have ST and if weighing was fully loaded.
Number of tires and axles.

Let's use a little "Cajun logic" and relate it to tire pressure. I don't go to the bank and withdraw $200 and toss $20 in the trash can on the way out the door. I don't go to Burger King, order two Whoppers and toss one in the trash on the way to the table, I don't buy tires with a specific rating and try to find ways to not use them fully.... If the tire is rated at 2400 lbs at 65PSI and 2800 pounds at 80 PSI, why toss that extra protection (weight carrying capacity) in the trash before hitching up the trailer???? Now, if that extra pressure was going to cause damage to the trailer, yes, I'd consider that aspect, but so far, NOBODY has ever documented to me that there is trailer damage incurred when running LRE tires at 80 PSI on a trailer suspension that was delivered from the factory with LRD tires rated at 65 PSI...... YMMV

[Genek]

I went from the same tire you had to the same E rated tires. My trailer is 10k gvw and runs about 9200 or so. I run my trailer tires at 80 psi and completely disregard the "tongue/pin weight". That is an ideal number but when you are driving down the road hitting frost heaves, pot holes, dips, jumps....each of those tires isn't carrying the "ideal" load. In many, if not most, they are way overloaded in some of those scenarios. As far as rougher ride, I've never seen it. Since going to the E tires vs the D tires my trailer actually rides better and nothing moves inside any longer. JMO/YMMV
Over or under pressure for your weight will cause improper wear of the tire. That’s the real issue with pressure rather than ride. We all know what a blow out costs us in damage to the trailer.

[sourdough]

Over or under pressure for your weight will cause improper wear of the tire. That’s the real issue with pressure rather than ride. We all know what a blow out costs us in damage to the trailer.

I agree. Ride is probably irrelevant in any conversation regarding trailer tires. As far as "improper wear", I've never owned a trailer tire that I didn't get rid of while it still looked brand new....never know...:)

[flybouy]

Well now, is your head spinning from all the numbers ?:dizzy: The numbers may look like they came from Vegas odds makers but I'll make it easy as some others have done. :cool:
Get your E rated tires and have them mounted and balanced with new valve stems (bolt in metal stems are best). The installer should check the rims for max pressure of 80 psi but remind them to check it. Also research your specific rim for how it needs to be balanced, lug centric or hub centric. Search the forum and www on that for more info.
If you don't have av TPMS buy one. Again search it, lot's of info out there.

Now go enjoy your camping! :camping:This is just my advice from someone that's pulled boats, campers, utility trailer, and farm equipment (in my youth, long before I was old enough to get a drivers license) for 50 + years. :D
YMMV

[jadatis]

Topicstarter was worried about needed pressure, and I gave some calc to show, what is important for that, nothing more.
But in the end it could show that he( or she) yust needs the 80 psi to have maximum reserve.
Not for no reason ST tires have a high failure-rate.
And the E load tires are placed , because the D- load had to low safety-reserve.

[CWtheMan]

Topicstarter was worried about needed pressure, and I gave some calc to show, what is important for that, nothing more.
But in the end it could show that he( or she) yust needs the 80 psi to have maximum reserve.
Not for no reason ST tires have a high failure-rate.
And the E load tires are placed , because the D- load had to low safety-reserve.

Here is one of the latest guides in print on the WWW that provides us with tire safety standards which also coincide with the governing bodies (DOT) regulations.

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

The Recreational Vehicle Industry Association (RVIA) is a membership organization that often requires it participating members – about 98% of the RV trailer manufacturers – to go beyond the minimum safety requirements established by the governing body/industry standards.

Their newest requirement for members is to have them apply an available 10% in tire load capacity reserves above the trailer manufacturer’s certified GAWR values. That would mean that tires fitted to a 6000# GAWR axle would have to provide 3300# of load capacity with a set recommended cold tire inflation pressure.

Within that same RVIA document is a recommendation to no longer fit RV trailer wheels 14” or larger with bias ply tires.

Those are also factors you should try to work into your responses.

[ChuckS]

New standard probably explains why Keystone changed tire load range from E rated to G rated from 2014 to 2015.

Same specs from manufacturer on exact same model in one year. Same 7K axles... just increased tire size. It was a smart move on their part because E rated 10 ply tires on any size Keystone Alpine won’t cut it.

[Tireman9]

Let's use a little "Cajun logic" and relate it to tire pressure. I don't go to the bank and withdraw $200 and toss $20 in the trash can on the way out the door. I don't go to Burger King, order two Whoppers and toss one in the trash on the way to the table, I don't buy tires with a specific rating and try to find ways to not use them fully.... If the tire is rated at 2400 lbs at 65PSI and 2800 pounds at 80 PSI, why toss that extra protection (weight carrying capacity) in the trash before hitching up the trailer???? Now, if that extra pressure was going to cause damage to the trailer, yes, I'd consider that aspect, but so far, NOBODY has ever documented to me that there is trailer damage incurred when running LRE tires at 80 PSI on a trailer suspension that was delivered from the factory with LRD tires rated at 65 PSI...... YMMV


Sorry, but you may have missed the point of adding a margin to the MINIMUM inflation. Maybe think this way. Assume your bank balance was tied to the DOW 500 with minuteby minute changes in value. If the value at 9AM was $1,123 and you knew you would be charged a $50 "Fee" if the balance dropped below $1,000 would you withdraw $123?


Your loading changes as you go around a corner. The Interply Shear (cause of belt separations) can go up by 20% or greater when you turn a sharp corner and your morning tire pressure will change by 2% for each change of 10°F. With o psi margin that means that every day you would have to adjust the pressure based on that days temperature. Not fun so why not include a "cushion" of +10 % so you would only have to add air if the temperature dropped 50°F.


Understand?

[ctbruce]

Sorry, but you may have missed the point of adding a margin to the MINIMUM inflation. Maybe think this way. Assume your bank balance was tied to the DOW 500 with minuteby minute changes in value. If the value at 9AM was $1,123 and you knew you would be charged a $50 "Fee" if the balance dropped below $1,000 would you withdraw $123?


Your loading changes as you go around a corner. The Interply Shear (cause of belt separations) can go up by 20% or greater when you turn a sharp corner and your morning tire pressure will change by 2% for each change of 10°F. With o psi margin that means that every day you would have to adjust the pressure based on that days temperature. Not fun so why not include a "cushion" of +10 % so you would only have to add air if the temperature dropped 50°F.


Understand?I read John's post as saying fill them up to cold max to gain all of the reserve capacity available to you based on the tires. It makes NO SENSE to buy tires with extra capacity and then run them at less air pressure and not use the reserve.

I believe you're both saying the same things.....at least this time! [emoji16]

[JRTJH]

Sorry, but you may have missed the point of adding a margin to the MINIMUM inflation. Maybe think this way. Assume your bank balance was tied to the DOW 500 with minuteby minute changes in value. If the value at 9AM was $1,123 and you knew you would be charged a $50 "Fee" if the balance dropped below $1,000 would you withdraw $123?


Your loading changes as you go around a corner. The Interply Shear (cause of belt separations) can go up by 20% or greater when you turn a sharp corner and your morning tire pressure will change by 2% for each change of 10°F. With o psi margin that means that every day you would have to adjust the pressure based on that days temperature. Not fun so why not include a "cushion" of +10 % so you would only have to add air if the temperature dropped 50°F.


Understand?

Why not just run the tires at the maximum recommended pressure and gain the full advantage of their weight carrying capacity? Of course, that would be the simple solution, without all the "caluclations and percentages" and would completely ignore the DOW 500.....

Maybe, just maybe, if you had some boudin for lunch, you'd understand "Cajun logic" but it appears you haven't yet indulged in such a feast..... Almost "sinful" Pauvre Bête

[CWtheMan]

Inflating tires on your trailer to the load carried is not the way it’s supposed to be done. That method comes from the commercial carrier industry and is really not applicable for vehicles, such as yours, built under the guidance of FMVSS.

Here is an excerpt from the RV section of the USTMA.

“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 pressures 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.”

In accordance with tire industry standards, inflation pressures for replacement tires must first be set to an inflation pressure that will ensure they provide a load capacity equal to or greater than what the Original Equipment tires provided.

[Tireman9]

I have made it quite clear in my blog. Motorhomes can adjust their inflation based on the actual measured load but multi-axle trailers should run the pressure associated with the tire max load.
This is not the same as considering you are throwing money away.


InterplyShear is the primary cause of belt separations in trailer application and you should run the higher pressure than what is needed to support the trailer load as this will lower, but not eliminate the Interply Shear in your tires.


Sometimes Finite Eliment analysis is not something that can be equated to gut feel.

[jadatis]

@ tireman 9


Does this interply- sheer story also goes for 1 axle trailers?
I asume trailers in America only have 2 axles or more. But in Europe most of the travel- trailers have 1 axle , and tandem- axle trailers are exeptional

[Tireman9]

@ tireman 9


Does this interply- sheer story also goes for 1 axle trailers?
I asume trailers in America only have 2 axles or more. But in Europe most of the travel- trailers have 1 axle , and tandem- axle trailers are exeptional
Single axle trailers probably have higher interply shear than a motorized but I don't have the data or other evidence such as a film showing the lateral bending of the tires as seen on my post in my blog on Interply shear.


Side bending would be proof of higher InterplyShear. I just can't put a number on how much higher.


The Vehicle simulation software and the Finite Element software to calculate the level costs about $300,000. I was lucky to get a single run after hours while working but since I am now retired do not have access to the software anymore.

[jadatis]

For good understanding, ply-shear is courced by sideward to the driving direction forces when cornering. Or did I understand wrong.
Forgive me then, English is not my native language, sertainly not the technical English.

That is the reason why I dont expect lateral forces being that large for single axle travel trailers.
Because those turn around the same centre as the rear- and front-wheels of towing vehicle.

[Tireman9]

For good understanding, ply-shear is courced by sideward to the driving direction forces when cornering. Or did I understand wrong.
Forgive me then, English is not my native language, sertainly not the technical English.

That is the reason why I dont expect lateral forces being that large for single axle travel trailers.
Because those turn around the same centre as the rear- and front-wheels of towing vehicle.
I agree. You can learn more about the Interply Shear by reading the couple posts on the topic in my tire blog.

[CWtheMan]

Reading tire documents from a scientific presentation is far beyond most tire user interests. Just about everything we use on a daily basis has a wear-out factor. In tire documents we are seeing the word fatigue quite often. It’s here in this document. Link it up with what just about any ST tire manufacturer says about their tires life expectance and you can clearly see why it’s 3-5 years for the ST tire. More than 15 years ago Carlisle told us about tire fatigue (degrading) and the 3-5 year life expectancy of their tires.

Here’s the read.

https://etda.libraries.psu.edu/catalog/6202