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Old 09-20-2009, 06:38 AM   #15
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Originally Posted by Beginner View Post
As I have stated before, the rubber compounds used to construct ST tires (65 mph Speed Rating) looses its integrity at a lower temperature than LT tires (Speed Rating 99 mph or so).
If you go to E rated tires you should run the same pressure as with the D rated tire or you will be beating the crap out of your trailer and there is always the good chance of having a wheel fail.
I run 60 psi in my load range D LT tires and in 3 years only had to add pressure once.
We don't need tires with more load range/higher inflation pressure, we just need better quality tires (Speed Rating of at least 99 mph)
Beginner
According the manufacturers spec sheets you're incorrect.

You can exceed 65 mph with ST tires, that is stated clearly on their inflation charts.

As far as running the same psi in D or E where did you get that info?
Why do you need speed ratings of 99?
Also "the rubber compounds used to construct ST tires looses its integrity at a lower temperature than LT tires"
Can you please substantiate that with authoritive documentation?

I just don't want others reading this miss info and buying worse yet inflating their tires incorrectly.


Generally speaking, the vehicle’s gross weight and divide this by two or four in order to roughly determine the load capacity for each individual tire. If the vehicle gross weight is 4,500 pounds, each tire should be able to safely support at least 1,125 pounds.
However, you should never select a tire that only meets this minimum weight capability.
Always select a tire that offers a greater, or reserve load capacity, which will help the vehicle handle and respond to higher-stress and higher-impact situations.

Look at the inflation chart for that weight and speed.

You can drive faster than 65 MPH but in order to do that, however, you need to increase your cold inflation by about 10 psi (without exceeding the maximum PSI stamped on the tire) for every 10 mph over 65 that you are going.

So if your chart indicated you needed 45 psi for your weight and you added 10 psi (or 55 psi) your rating is now 75 mph, if you added 10 more ( 65 psi) your rating is 85 mph.

Mine called for 50 psi on those charts, I run 65.

I often travel on good roads at 70-75 mph over the last 3 years and maybe 30,000 miles.
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Old 09-20-2009, 07:17 AM   #16
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Tires

ROBERT SUNRUS
I see by your stat page that you drive a 2000 Lincoln Navigator. What tires do you have on it?
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Old 09-20-2009, 07:22 AM   #17
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What tires do you have on your Tow Vehicle or Family Sedan?
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Old 09-20-2009, 09:42 AM   #18
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Looking at the load/inflation tables for ST tires I've noted a curious thing. While the load for E rated tires at maximum pressure (80 lbs) is about the same as for LT tires (2830), the load for D rated tires at maximum pressure (2540) is markedly higher than a D rated LT tire. I've settled on "D's" since I'm concerned about the stress that E's would put on the trailer at higher pressures.
Not sure what you are saying here. You are comparing a tire rating (E) to a tire type (LT). With in a given type of tire you can have C D and E rated loads and as the letter rating goes up so will the load rating for a give type and size.

http://www.goodyear.com/rv/pdf/rv_inflation.pdf

Running E rated tires at the correct pressure for the load they carry will not effect ride quality.

Note I have posted a Goodyear chart only because it is an easy one to find. All tires of the same type and size have the same load ratings by government standards.
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Old 09-20-2009, 11:41 AM   #19
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What tires do you have on your Tow Vehicle or Family Sedan?
Beginner
On my truck 2500HD I a Bridgestone Duravis II, E load at 55/65 empty or not towing.

Towing 65/80
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Old 09-20-2009, 09:58 PM   #20
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ROBERT SUNRUS
I see by your stat page that you drive a 2000 Lincoln Navigator. What tires do you have on it?
Beginner
Hi, Beginner. The tires on my Lincoln are:

Goodyear Eagle GT II....P275/60R17.....110T....2337 lbs max at 44 lbs cold inflation.

Ford says, to run 26 lbs front & 33 lbs rear. And Bob says, run 35 lbs front & 40 lbs rear while towing.
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Old 09-22-2009, 01:00 AM   #21
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D vesus E

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Your tires are the Duravis M77311II I have to assume. According to Tire Rack those tires if a 245/75R16) carry the specifications of 120/116R E (Speed Rating of R which is 106 MPH. If it’s the 265/75R16 they carry the specifications of 123/120Q (Speed R
ating of Q which is 100 MPH) according to this website:

http://www.tirerack.com/tires/Spec.jsp?make=Bridgestone&model=Duravis+M773II&tir ePageLocQty=
ROBERT SUNRUS, your tires are Speed Rated at 110T or a Speed Rating of 118 MPH according to the web site noted above.
Why are you two wasting your money on those tires or do both of you drive the unhooked tow vehicles a 100 MPH?
There are tires available with a Speed Rating of K ( 68 MPH) and L (75 MPH) which according to your arguments would serve you just fine and are probably cheaper.
As per LI Pets request I will endeavor to find the information from a engineer or engineering journal or on a mfgs website.
Just remember this, by your criteria of authoritative certification requirements, Einstein as a young man in his late 20s could not get a job with our Government today as much more than a laborer and Our Lord could not qualify for a Commission in the Chaplains Corps (I hope I used the proper nomenclature) in any branch of the armed services.
Edison would not be eligible either.
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Old 09-22-2009, 07:23 AM   #22
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Bottom line is you are incorrect about ST tires, you must stop repeating that information.

That question was asked by you to tell us the ratings of our tires, didn't need you for that thanks.

Those are tires that came from GMC on the truck and at $140 per are not a lot of money.

Not towing, I will from time to time go faster.

You said "As per LI Pets request I will endeavor to find the information from a engineer or engineering journal or on a mfgs website."

You tried that line many times here before about talking to some engineer, forget it .. that's unacceptable.

I would like two authoritative sources to support your theory
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Old 09-22-2009, 10:22 AM   #23
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OK so we know your two opinions and they don't mesh. Unless either one of you are going to present new data, please do not make statements about how the other is wrong. Or any other type of judgements.

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Old 09-22-2009, 11:43 AM   #24
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Quote:
Originally Posted by LI Pets View Post
According the manufacturers spec sheets you're incorrect.

You can exceed 65 mph with ST tires, that is stated clearly on their inflation charts.

lso "the rubber compounds used to construct ST tires looses its integrity at a lower temperature than LT tires"


I just don't want others reading this miss info and buying worse yet inflating their tires incorrectly.


You can drive faster than 65 MPH but in order to do that, however, you need to increase your cold inflation by about 10 psi (without exceeding the maximum PSI stamped on the tire) for every 10 mph over 65 that you are going.

So if your chart indicated you needed 45 psi for your weight and you added 10 psi (or 55 psi) your rating is now 75 mph, if you added 10 more ( 65 psi) your rating is 85 mph.

Mine called for 50 psi on those charts, I run 65.

I often travel on good roads at 70-75 mph over the last 3 years and maybe 30,000 miles.
This information is provided at the Goodyear web site.

Industry standards dictate that tires with the ST (Special Trailer) designation are speed restricted to 65 mph under
normal inflation and load conditions, unless a different speed restriction is indicated on the sidewall of the tire.
Based on industry standards, if tires with the ST designation are used at speeds between 66 and 75 mph, it is
necessary to increase the cold inflation pressures by 10 psi above the recommended pressure for the load.
• Do not exceed the maximum pressure for the wheel.
• If the maximum pressure for the wheel prohibits the increase of air pressure, then the maximum speed must be
restricted to 65 mph.
The cold inflation pressure must not exceed 10 psi beyond the inflation specified for the maximum load of the tire.


I want to add some clarification here. First there is no blanket rule that states that you add 10 lbs for every 10 miles per hour that you want to exceed the max speed rating of the tire. I've included Goodyear's statement that only supports 10 psi over sidewall limitations.

I have been to a tire training safety seminar that is put on by A Weigh We Go which promotes RV tire safety. MotorHomeAdvice.com - Articles >

The key issue is here is heat buildup in tires and the amount of flex that the tire generates. The faster you go, the more heat you build up in the tire. The lower the pressure, you increase the flex and again a byproduct is heat.

Speed rating is important since it indicates the tires ability to withstand heat and dissipate that heat. The reason why Goodyear states you can increase the inflation load by 10 psi is that the tire will have less flex which offsets the higher rotation speed (which increases the amount of flex and heat generated). Another example of speed issues is the fact that Airstream states you can pull a trailer with one tandem tire missing. Note however they limit the speed to 45 mph and 50 miles. Why? Because a tire rotating at a lower speed has a higher load limit and therefore the heat load generated by the increased load (and greater tire sidewall flex) is offset by the lower rotation speed.

So we can talk till the cows come home but ST tires do have advantages over LT's, one being UV protection (more), and sidewall flexability (ability to handle the pivot that occurs on tandem axles on tight turns). The liability side though is the speed limitations. And once you exceed the speed limitation stamped on the sidewall (without that 10psi adjustment), you increase the sidewall flex (due to the tires turning faster). That generates heat and those tires do have heat limitations. Whether it's the rubber compound, or the construction method, its physics. So if you want to drive fast, put on an LT. Obviously it has it's limitations but speed won't be the major factor.

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Old 09-22-2009, 02:15 PM   #25
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Quote:
...Speed rating is important...
YES IT IS!

but only for tires that CARRY a speed rating.

and ST TIRES DO NOT HAVE A SPEED RATING...

that is the problem with the 100s of posts by one person and the 1000s of posts that repeat this FACTUALLY INCORRECT INFO...

ST tires are LOAD RATED at the industry standard (for st tires) of 65 mph.

in other words the LOAD RATING is established at 65 mph.

but THEY ARE NOT SPEED RATED following the standard approach to speed rating.

http://www.airforums.com/forums/595219-post42.html

IF they were speed rated (using the accepted techniques) gy would NOT give any guidance on towing faster than 65mph ...

because BY DEFINITION exceeding a GENUINE SPEED RATING by 10 mph, WILL CAUSE THE TIRE TO FAIL within 10 minutes.

that is HOW current P/LT tire speed ratings are established.

tires are taken to a given speed and pushed TO FAILURE.

that isn't how gyms are tested and it isn't how they are rated.

most tires that are labeled P or LT are speed rated BUT NOT ALL tires are speed rated.

and NO currently produced domestic market ST tires carry a speed rating.

Tire code - Wikipedia, the free encyclopedia

P and LT tires (almost all) carry UTQG ratings now too, but ST tires are NOT utqg rated, just like they aren't SPEED rated.

now for a PERSONAL OPINION on SPEED and LOAD with regard to ST tires...

-weight EACH contact point on the trailer, IF any exceed the tire or wheel rating, FIX THE ISSUE...

-IF the load is VERY CLOSE to the tire LOAD RATING be careful about going over 65 mph.

-IF the load is UNDER the LOAD RATING significantly (several hundred lbs) then be sure the tire is INFLATED to max sidewall pressure before towing OVER 65 mph.

-HIGHER speeds may ACCELERATE wear or REDUCE load capacity...

-don't come crying here if ANYTHING bad happens towing at higher speeds, it was YOUR choice.
__________________________________

it's a bit like the confusion rdm' tired to clear in post #4 about plys...

and FOR THE SAKE of DIESEL EAGLE (the o.p) expanded a bit here...

http://www.airforums.com/forums/433671-post3.html

and here...

http://www.airforums.com/forums/f438...ply-35173.html

and here...

http://www.airforums.com/forums/f438...tml#post595219

D vs E is REALLY the topic of this thread BEFORE IT WAS HIJACKED in post #11...

with the REPEADEDLY incorrect info about speed ratings that DO NOT EXIST for these st tires.
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imo the ONLY thing LI' is doing is asking for CREDIBLE references for the bogus st info, regularly posted by another member.

'pets is doing everyone HERE a favor by questioning this incorrect and MISLEADING stuff about st tires.

many of us have offered posts to COUNTER this incorrect stuff or have asked for REFERENCES.

but we eventually tire of trying to balance the BAD info with good, and the BAD just keeps getting posted OVER and OVER.
__________________________________

on a RELATED issue,

there is a difference between tires with an st tire LOAD RATING and a P/LT tire LOAD INDEX...

this is ONE of reasons why trying to select and use LT tires for towing is tricky,

because the LOAD INDEX of LT tires doesn't EQUAL the LOAD RATING of ST tires...

folks confuse this issue regularly which is understandable, but WE do NOT need to perpetuate it...

just like we don't need to perpetuate the MISLEADING NON-EXISTENT speed rating for ST tires...

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here's an example of ANOTHER passenger tire vs ST tire issue...

drivers may discover a P/LT tire is under inflated while driving, for example 10-15 psi UNDER the recommended pressure, way 35psi...

those LT/P tires that are under inflated by 30-40% can be correctly inflated and continue IN SERVICE.

but an ST tire that is used for as little as 50 miles UNDER inflated by 30%, SHOULD BE REPLACED, not used...

this is a critical issue, because LOTS of folks tow on 1 or 2 under inflated ST tire, eventually ADDING AIR and continuing to use it...

DOING THAT is against ALL of the ST tire guidelines and is probably why THOSE TIRES (used after under inflation) FAIL in service.

so ST tires vs LT/P tires are used, abused, replaced and inflated under DIFFERENT GUIDES and their service life and parameters are DIFFERENT.

yet how many folks HERE routinely REPLACE a newer or well 'tread' ST tire, just because it's been used some UNDER inflated?
________________________

back to the never ending threads on hot topics,

try looking at this whole thing from another angle...

IF someone was repeatedly posting that a/s trailer skin panels are GLUED together (the rivet heads are cosmetic only) ...

or that ALL a/s trailers are SQUARE...

would those misleading bits be allowed, OVER and OVER and OVER again?
____________________________________

so does this post EXCEED the speed rating for the forums OR is INCORRECT info ok here, as long as it is posted NICELY???

cheers
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Old 09-22-2009, 03:11 PM   #26
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Quote:
Originally Posted by 2airishuman;

so does this post EXCEED the speed rating for the forums OR is INCORRECT info ok here, as long as it is posted NICELY???
cheers
2air'
NO.....You are well under the speed limit, and it was a VERY nice post.

think I'll go toe at 99
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Old 09-22-2009, 03:38 PM   #27
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I will note that I fell into a terminology gap in stating speed rating vs load rating. 2air is correct in that load rating is the proper terminology. I think if you take my post and replace the word speed with load, the information given still carries the same impact.

While the term speed rating is incorrect I'm hoping that everyone does understand that speed in conjunction with tire pressures does affect load capacity of a tire which ultimately affects the lifespan of a tire. It's heat that kills the tire and if you drive faster that the load rating on the tire (and dependent upon the load you are carrying) that tire will heat up. If you under inflate (and therefore possibly overloaded) the tire will heat up and you stand the chance of breaking belt components due to excessive flexing.

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Old 09-22-2009, 04:05 PM   #28
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2air

Thanks for the post.

I have one question on the Tire Code tread you noted. They state "Prior to 1991 tire speed ratings were shown inside the tire size"before the "R" character. I could not find an explanation on that page as to where that code is shown now.

Studying my E rated 2680 lbs. rated Michelin LT 225 75 R16s I don't see any notation for speed or temperature. While I am sure they exceed anything I will need I ask this for others that may be running LTs.


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