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Old 11-29-2018, 01:17 PM   #21
JRTJH
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Originally Posted by jadatis View Post
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
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Old 11-29-2018, 09:38 PM   #22
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Originally Posted by sourdough View Post
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.
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Old 11-29-2018, 09:44 PM   #23
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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...
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Old 11-30-2018, 03:14 AM   #24
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Some experience related advice.

Well now, is your head spinning from all the numbers ? The numbers may look like they came from Vegas odds makers but I'll make it easy as some others have done.
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! 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.
YMMV
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Old 11-30-2018, 03:31 AM   #25
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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.
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Old 11-30-2018, 09:16 AM   #26
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Quote:
Originally Posted by jadatis View Post
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/defaul...TruckTires.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.
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Old 11-30-2018, 10:03 AM   #27
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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.
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Old 12-06-2018, 07:50 AM   #28
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Originally Posted by JRTJH View Post
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?
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Old 12-06-2018, 08:03 AM   #29
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Originally Posted by Tireman9 View Post
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!
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Old 12-06-2018, 10:51 AM   #30
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Quote:
Originally Posted by Tireman9 View Post
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 Bęte
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Old 12-06-2018, 02:56 PM   #31
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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.
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Old 12-06-2018, 07:26 PM   #32
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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.
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Old 12-07-2018, 04:30 AM   #33
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@ 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
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Old 12-07-2018, 07:57 PM   #34
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@ 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.
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Old 12-08-2018, 03:18 AM   #35
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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.
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Old 12-08-2018, 10:16 AM   #36
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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.
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Old 12-23-2018, 03:25 PM   #37
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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
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