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Old 06-29-2016, 08:49 AM   #15
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Originally Posted by 1bigmess View Post
Until the OEM tires are replaced with non-OEM tires.

Actually the recommended inflation pressures for any OEM tires are used to establish new recommended inflation pressures for replacement tires of another size or design or both.

Clearly presented industry standards for that statement can be found in a PDF about "Replacement Tire" procedures by Firestone/Bridgestone.
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Old 06-29-2016, 11:07 AM   #16
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I've been taking my advice on trailer tires from a tire engineer. If I need aircraft advice, I know who to go to. Thanks.
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Old 06-29-2016, 03:04 PM   #17
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I've been taking my advice on trailer tires from a tire engineer. If I need aircraft advice, I know who to go to. Thanks.
Often times tire engineers know how to construct tires and test them but know little about government regulations that allow them to be used or the tire industry standards that are standardized to maintain them.

All I did was provide a link to a document with approved tire industry standards for replacement tires.

According to tire industry standards any tire approved as a replacement for an Original Equipment tire must have a load capacity equal to or greater than the OE tire. That's by inflation.
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Old 06-29-2016, 03:29 PM   #18
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Often times tire engineers know how to construct tires and test them but know little about government regulations that allow them to be used or the tire industry standards that are standardized to maintain them.
Wow. Ok, um, like I said before. I have no airplane questions, so I'm very much done here.
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Old 06-29-2016, 07:09 PM   #19
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When I had my motorhome, I weighed it as for travel and full water tank. I then used the Goodyear weight recommendation for 19.5 inch based on weight. My tires had 110 lbs on sidewall but I used 92 lbs. However, as others have said, a trailer ST tire is different and use max weight on sidewall. My trailer tires says 50 lbs so I use 50.
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Old 06-30-2016, 11:49 AM   #20
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Here again I may seem overbearing about this subject and maybe I am. However, there are all sorts of misconceptions about tire inflation pressures and nobody needs that. It’s just to important to have your automotive and trailer tires set at the correct inflation pressures, all the time.

For automotive and RV trailer tires the correct inflation pressures are always going to be what the vehicle manufacturer has recommended and displayed on the vehicle’s certification label, tire placard, or in the vehicle owner’s manual for the Original Equipment tires. Not only is that the correct inflation pressure its also the minimum pressure and the benchmark for all replacement tires.

Nothing in the industry standards or regulations disallows inflation pressures in between what has been recommended and the maximum found on the individual tire.

Inflating your tires to the load carried is an unacceptable practice in the automotive industry. Why? FMVSS regulations require the vehicle manufacturer of such vehicles to provide load capacity reserves above GVWR. Why would you do less?

Trailer tires (ST) are built to a different standard. Mostly because trailer manufacturers do not have to provide load capacity reserves above GAWR. ST tire builders insure us that such tires are designed to be inflated to full sidewall pressures, all the time. Trailer builders may or may not provide some reserve load capacity with their OE tire selections. I have yet to see a certification label for a trailer equipped with ST tires with recommended tire inflation pressures below sidewall maximum pressures. I have more than 100 pictures of certification labels I took at RV shows. Here is an example.

http://www.irv2.com/photopost/showfull.php?photo=22027
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Old 06-30-2016, 12:22 PM   #21
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Here again I may seem overbearing about this subject and maybe I am.
(SNIP)
I have yet to see a certification label for a trailer equipped with ST tires with recommended tire inflation pressures below sidewall maximum pressures.
You said that ST tires are different, and they most certainly are. Due to interply shear that trailer tires experience in multiple axle configurations, they must be inflated to their maximum sidewall pressure.

Again, multiple axle trailers experience a condition that LT and P tires do not, and that is the reason they are different, and that is the reason they must be inflated to their maximum sidewall pressure.

It seems to me your particular issue is due to not understanding this particular problem, interply shear, and the resulting trailer manufacturing industry standard of inflating ST type tires to their max rating even in the rare circumstances when it may not be necessary. The trailer manufacturers may be making an unnecessary pressure recommendation with single axle trailers, but not with multiple axle trailers, when they slap a sticker on there that tells the operator to inflate ST type tires to their max sidewall molded or branded inflation pressure.

RV Tire Safety: "Interply Shear" and other Techno Babble
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Old 06-30-2016, 01:40 PM   #22
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Checked tire pressure and all 4 were at 35lbs from last year. They look ok but max cold pressure on tires is 50 lbs. That seems too hard--any comments ? Also had a new hot water tank [Atwood] installed and I'm waiting for a manual, meanwhile , the pilot shuts off from time to time and can't figure why.
You have an RV certification label on driver side at the front of the trailer. That has tire size & minimum inflation information as well as max load for axles and RV. A competent dealer should have pointed this Safety information out to uou but that may be expecting too much as it seems that many RV salesmen might have been pushing washing machines last month for all the knowledge on the technical side of the product they sell that they demonstrate.
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Old 06-30-2016, 01:51 PM   #23
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Too low of pressure in your ST trailer tires causes excessive heat build up. Not good �� Most likely they will need to be at 50 PSI. All the RV Trailers I have had were set at 50 psi.
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Old 06-30-2016, 01:57 PM   #24
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As a trailer goes down the road and around curves, does the load remain static on each tire?
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Old 06-30-2016, 02:01 PM   #25
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If they are ST tires, they should always be at max pressure even when not at max capacity.
I have been told the exact opposite. Most don't care about wearing out the trailer tires as they will age out before they wear out, but too much pressure will wear the center faster. And then, it depends what you are hauling, as tires are part of the suspension. Don't believe me?? Ever ridden on solid tires? Ever wonder why you don't air your car tires to max? Ever aired your car tires to max and noticed the ride?

Now, if you're carrying something that doesn't need suspension, like my car hauler, then air 'em up to the placard limits. It keeps the tires a bit cooler, as less rubber is on the ground. The suspension of the car I'm carrying will protect my car. However, my horse trailer is something different. I don't want the ponies pounded any more than the minimum, so I air the tires to the pressure for the weight of the loaded trailer. If you think your travel trailer or fifth wheel can take the pounding, then, by all means, air them up solid as a rock and save a few pennies in fuel. Don't be surprised to find your closet doors laying on the floor.
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Old 06-30-2016, 02:07 PM   #26
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Don't want to step on toes with the interesting back and forth in this thread but I have some observations.

Yes I designed tires. I also tested them and even ran a race team sponsored by a tire company. I also interacted directly with DOT in Washington and RMA in Akron and was responsible for ensuring that company standard practice followed the federal Regulations. So I may have a bit of first hand knowledge.

A couple of things I do know. The Federal Regs are sometimes shaped by what lobbyists want not what Engineers say would be a better practice. Some Industry Standards are decades out of date because there is resistance to change from some quarters.

Inflating to the placard is not wrong, as long as the RV weight is known. A big assumption that is factually wrong is that the weight is equally distributed between axles on trailers and 50/50 side to side on all axles of RVs. This is why I and some others suggest that all RV owners learn the actual load on each tire position and ensure they have a 15% margin.
I read claims that ST tires have different construction (which may be true) to address the high bending loads experienced by trailers ( this part I doubt as there is no industry or Federal test for this so I do not know there can be a meaningful measurement for "sidewall stiffness" in ST tires. In fact Finite Element analysis identifies that trailers do impart significant unique loading on tires but so far I have not seen anyone stepping up and demonstrating a willingness to address this issue for to do so would require more expensive tires to be placed on trailers and the RV industry is adamantly opposed to any move in that direction based on information I have received.
The best I can do to address the Interply Shear which is a real physical force not mentioned in any standard or regulation, is to offer the suggestion to multi axle trailer owners to run the sidewall max inflation in addition to having at least a 15% margin in load capacity. Also running TPMS and doing an inspection as outlined in my blog are good extra precautions.
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Old 06-30-2016, 02:10 PM   #27
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As a trailer goes down the road and around curves, does the load remain static on each tire?
Absolutely not. I don't have the data right in front of me but if I recall correctly you can expect load shifting due to curves, wind and slope of roadway to be in the range of +/- 15%
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Old 06-30-2016, 02:11 PM   #28
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I have been told the exact opposite. Most don't care about wearing out the trailer tires as they will age out before they wear out, but too much pressure will wear the center faster. And then, it depends what you are hauling, as tires are part of the suspension. Don't believe me?? Ever ridden on solid tires? Ever wonder why you don't air your car tires to max? Ever aired your car tires to max and noticed the ride?

Now, if you're carrying something that doesn't need suspension, like my car hauler, then air 'em up to the placard limits. It keeps the tires a bit cooler, as less rubber is on the ground. The suspension of the car I'm carrying will protect my car. However, my horse trailer is something different. I don't want the ponies pounded any more than the minimum, so I air the tires to the pressure for the weight of the loaded trailer. If you think your travel trailer or fifth wheel can take the pounding, then, by all means, air them up solid as a rock and save a few pennies in fuel. Don't be surprised to find your closet doors laying on the floor.

No problem and I understand your concern. Just do not be surprised if your tire life is reduced with a tire failure
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