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Old 06-29-2014, 01:43 PM   #15
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Originally Posted by elliott-maine View Post
The most accurate way to determine the tire pressure to use is to have each wheel weighed separately, and use the manufacturer's inflation guide. Use the heavier weight on each axle to determine the weight. Otherwise, use the sidewall pressure to be safe.
This is a true statement. As long as we know the tire is not overloaded there is no damage done to run at max pressure even if not needed. We will age out tires before wear is a consideration.
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Old 06-29-2014, 03:21 PM   #16
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Many, not all, tire manufactures of ST tires states you can run them at speeds over 65 if you add 10# air to max. Personally we won't run ST tires.
sometimes its even better to give the ST tires that 10 psi extra above that pressure needed for the maximum load ( wich is not the maximum pressure of the tire) even if speed is below 65m/h.

ST tires are often put on Trailers and 5th wheelers with yust enaugh loadcapacity to carry the Gross axle weight rating.
and because ST s are calculated in their maximum load for more deflection allowed for the lower speed then the same tire in LT, its better to give them that lesser deflection of LT to make them last longer and make chanche on tire failure minimal.

That is also needed in addition to my former post .
I only mentioned the GVWR ( gross vehicle weight rating), but would also like the GAWR ( gross axle weight rating) of all the axles.
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Old 06-29-2014, 07:35 PM   #17
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I run my E`s at 80 psi cold, and the TPMS on a 90 degree day towing about 200 miles they run up to 88psi
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Old 06-29-2014, 08:41 PM   #18
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I run my E`s at 80 psi cold, and the TPMS on a 90 degree day towing about 200 miles they run up to 88psi
Yes, this is normal. The 80 psi is cold settings. Manufacturers allow for this
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Old 06-29-2014, 10:08 PM   #19
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OK, Iíll do this the hard way. The tire pressures found on your trailerís certification label/tire placard is always the correct tire pressure for Original Equipment (OE) tires and replacement tires of the same design and size as the OE tires. Even tires of the same design and size with a higher load capacity will have the same load capacity as the OE tires when aired to the placard pressures.

Industry standards for replacement tires require the tire installer to use tire pressure for the replacements that will provide the same amount of load capacity as the OE tires. The tire installer should inform the owner of the new recommended air pressures, make a note in the vehicle ownerís manual and install an auxiliary tire placard adjacent to the original tire placard. You may not ever seen it done but thatís the procedure. Owners should follow that procedure when installing replacements at home.

Industry standards will NEVER recommend air pressures lower than the amount needed to provide the load capacity of the OE tires.

Itís a fact! Vehicle manufacturers of RV trailers are responsible for setting the recommended (correct) cold tire pressures. Tire manufacturers provide maximum load capacities for the tires they build along with the air pressure necessary to support those load capacities. That information is found on all tire sidewalls. The Tire & Rim Association (TRA) in conjunction with tire manufacturers provide load inflation charts vehicle manufacturers use for tire selection and fitment to your trailers.

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Old 06-30-2014, 08:25 AM   #20
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Is there any reason not to go ahead and run the max tire pressure noted on the side wall. This seems like it would be the best insurance against tire failure. After all the tires are going to age out before any ware pattern might reveal center ware. Seems to me that this would provide the most safety as well as helping to tire to stay as cool as possible. I know that the unit will have a harsher ride but you are not riding in the 5er.
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Old 06-30-2014, 08:35 AM   #21
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Is there any reason not to go ahead and run the max tire pressure noted on the side wall. This seems like it would be the best insurance against tire failure. After all the tires are going to age out before any ware pattern might reveal center ware. Seems to me that this would provide the most safety as well as helping to tire to stay as cool as possible. I know that the unit will have a harsher ride but you are not riding in the 5er.
There is nothing in any of the rules that disallow higher air pressures than what the vehicle manufacturer has recommended.

The tires must have the ability to sustain the higher air pressure and the rims must also be rated for the potential extra load.

Itís much easier to balance your axle loads when there is extra load capacity beyond the vehicle manufacturerís recommendations. Thatís where the advantage of ďplus sizingĒ your tires can be utilized.

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Old 06-30-2014, 09:08 AM   #22
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@ gregk
To use your own words, is there any reason not to let everybody wear shoesise 14.

Its never bad for the tires to use high pressure , sometimes even higher pressure then the pressure needed for the maximum load would be better ( AT yyy psi) wich is not the maximum pressure of the tire.

Though your not in the Trailer so wont have comfort problems , Screws in woodwork might tremble loose from the bumping of to hard pumped tires.

I once introduced the Load% wich is what % real load on tire is of the loadcapacity calculated for the pressure.
So for instance for AT pressure is 2000 lbs calculated so is maximum load.
Then I state that under 85% gives discomfort for persons and animals, 85% of 2000= 1700 lbs.
Under 80% bumping gets that bad that the schrews can tremble loose for trailers, so 80% of 2000 is 1600 lbs . Then still at 1600lbs realy on tire screwloos border.

So there is a large range in wich tires last long and comfort and gripp is acceptable. Over 2000 lbs gives tire damage but only when driving the speed this maximum load is calculated for ( ST 65m/h, LT mostly 140km/87m/h). for lower speed used as max even more loadcapacity.

This load% is verry discussable and I determined it for an average tire with higher Hight width division and speedcode from Q = 160km/99m/h.

So an ST tire wich is calculated in its maximum load for 65m/h it gives even 18% more maximum load then for 160km/99m/h calculated and 12% more then for N speedrated (140km/87m).
This makes that ST tires can go higher in its pressure advice before bumping border or screwloose border is reached. The tire of example would have 2240 lbs maximum load if it was placed in the market as an ST tire. But then still when realy 1600 lbs on tire screwloos border.
The other way around if with this LT tire of 2000 maxload you never drive faster then 65m/h , when realy 2240 lbs is on tire so Load% is 112% its yust at the damage border.

For fuel saving also high pressure on TT and 5thwh has marginal effect, because the energy loss for the tires is about nothing to that by air-resistance of the big shoebox on wheels.
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Old 06-30-2014, 09:20 AM   #23
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So if we run tires that can handle more weight than the trailer is it will ride like my dually when it is empty?
So that is why they publish tire pressure for weight tables?

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Old 06-30-2014, 09:48 AM   #24
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So if we run tires that can handle more weight than the trailer is it will ride like my dually when it is empty?
Your trucks owner's manual may have other recommendations for normal load conditions.
So that is why they publish tire pressure for weight tables?

Load inflation charts are developed by the tire industry primarily to assist vehicle manufacturers in their tire selections and fitments. They are also routinely used by the trucking industry.

Nearly 100% of tires fitted to RV trailers have recommended tire pressures equal to the maximum load capacity of the installed tires. The builder of those tires insure the vehicle manufacturers that their tires can be operated at those pressures continuously. In fact, some even make it a tire warranty requirement.

I would not venture to guess what the percentage of RV trailer owners would weigh their rig before every trip. Iíll bet itís a very low number. Even then, all they can do is make sure their trailer isnít overloaded and that the load is balanced between the axles and on the axle ends.

Itís pretty much proven by all the reports we read on RV trailer tire forums that fooling around with tire pressures is not a thing to do. Insure that your tire gauge is accurate and follow the vehicle manufacturerís air pressure recommendations are my recommendations.

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Old 06-30-2014, 01:33 PM   #25
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If you have not had the trailer since it was new, verify the correct tires are on the trailer before using the placard pressure.

For inflation charts:
Goodyear has a RV tire and care guide that tells you how to weigh all 4 corners, and gives you an inflation chart.
The guide explains of course.
Michelin has one also.
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Old 06-30-2014, 02:05 PM   #26
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Here is a good reference to use when going to the scales.

http://www.trucktires.com/bridgeston.../WeighForm.pdf

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p.s. The following statement is part of the reference dialog for finding the correct air pressure.

ďNever use inflation pressures lower than those printed on the vehicle placard.Ē
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Old 07-01-2014, 10:21 AM   #27
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Thanks for all the info on inflation of tires.
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Old 07-01-2014, 09:02 PM   #28
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Goodyear says this about tire pressure for trailers.

Goodyear Tire and Rubber .... weighing RVs
Special Considerations

Unless trying to resolve poor ride quality problems with an RV trailer, it is recommended that trailer tires be inflated to the pressure indicated on the sidewall of the tire. Trailer tires experience significant lateral (side-to-side) loads due to vehicle sway from uneven roads or passing vehicles. Using the inflation pressure engraved on the sidewall will provide optimum load carrying capacity and minimize heat build-up."

Some folks use Carlisle ST tires. It in their warranty the max sidewall pressures are required.

Tireman9 one of our tire engineers also recommends max sidewall pressures says; from rvtiresafety.com his online tire blog;

"The manufacturers do not take into consideration the side to side unbalance, as to do so would require them to provide larger (more expensive) tires. The other thing RV industry does not take into consideration is the forces to the tire structure due to running close axle spacing. Engineering analysis shows that when turning corners the forces trying to tear the tire apart can be over 20% higher in multi-axle applications than with tires at the corners of the vehicle.
The only options for the trailer owner are to up-size the tires (if there is room) or up-rate and increase inflation (if a higher Load Range tire and stronger wheels are available). Lacking the above being sure to run the tire at the inflation shown on the sidewall (i.e. max) will slightly decrease but not eliminate the overload forces.
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