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Old 10-13-2013, 11:12 AM   #41
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Originally Posted by Windywest View Post
Just because you have tires that can carry 2800 lbs doesn't mean you will. My rv is 7200 dry, I don't ever expect to travel with even close to my 9100 gvw. I have lr e tires, I will run them ot 65 psi, and should carry great. The air space in a lr c and a lr e tire of the same size is identical, only the container is different.
According to other posts here, running LR E tires at 65 psi, when they are rated at 80, increases the side load on the tire during turns ( especially getting into tight sites) and may lead to premature failure.

Just repeating what was posted.
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Old 10-13-2013, 11:25 AM   #42
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It is a fact that under inflated tires are dangerous.
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Old 10-13-2013, 12:21 PM   #43
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Originally Posted by garbonz View Post
According to other posts here, running LR E tires at 65 psi, when they are rated at 80, increases the side load on the tire during turns ( especially getting into tight sites) and may lead to premature failure.

Just repeating what was posted.
garbonz, you are correct. I read all the debates on this issue. The misleading thing to me is the manufacturer inflation charts. Yet no matter if you run your tires low they will cause you premature failure. My mane reason to move up to to a higher rating was not to be able to overload my axle, but to give me the extra strenght or plys which will take some worry away from me. Fr will tell you that they put on that garbage because people will over load thinking that the tire will hold it. It's just that they do not want to spend the extra money to install a good tire. For some reason as other industries think people are stupid. I have never ever heard of some these tire manufacturers that come on most trailers. My point is try to find a Trail Express dealer, besides lionhead. I couldn't. Goodyear and any other tire shop that I have talked to always said to run at the cold pressure rating, not one recommended that I run at 55 lbs because of my weight and not the 65 lbs that they are rated at.
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Old 10-13-2013, 02:12 PM   #44
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Here's the tire inflation charts for Maxxis tires, note the inflation PSI in relation to load. http://www.maxxis.com/Repository/Files/m8008load.pdf

As per the chart, with tire size 225 75R 15 having a load of 2270 requires 55 PSI. 55 PSI is above the Load range C tires, so it is a Load Range D tire at 55 PSI. The only difference between a Load Range D and E tire is the tread ply, the sidewalls are the same ply only I suspect the E is a bit stronger. That being said, the D tire and E tire are identical, the tire pressure is the same inside, and if the load is considerably less than what either a D or E would carry, why would the sidewalls flex anymore with one and not the other, since it's the air at 65 psi that carries the load, not the tire. The tire is just the container or the air. A LR E tire is just a stronger container, but the air volume is the exact same in a LR C, LR D or LR E tire. Think a balloon and a basketball of the exact same size. They both carry the same air, but one is a lot more stronger than the other, just have a kid sit on one at a birthday party and you'll see my point.
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Old 10-13-2013, 02:12 PM   #45
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Here RV Tire Safety is the link to an excellent blog on tires. Here http://www.maxxis.com/Repository/Files/m8008load.pdf is a link to a load/inflation chart from Maxxis. After reading all this stuff, it is hard to see why running a load range D tire at less than its maximum psi, but more that needed for the load would be a bad thing. I certainly plan to go to LR D when I change out tires. I did chase down my rims and found they are rated for 2150 lb or 65psi. Doesn't seem consistent, but I guess you could run 65 PSI, but still stay under the 2150 lbs, and be ok. After reading Mr. Marble's excellent blog on tire safety, I do plan to go out today and buy a TPMS.
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Old 10-13-2013, 03:24 PM   #46
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Originally Posted by Ford Idaho View Post
It is a fact that under inflated tires are dangerous.
Just curious, what is the actual definition of an under inflated tire ?

In my opinion, it is a tire that doesn't have enough air pressure for the load. If you have Load Range E tires, and a load of 1800 lbs per tire, do you need to pressure them up to be able to carry 2800 lbs ?

I have a friend who owns his own fencing company, he has a tandem axle flatdeck trailer which sometimes carries over 10,000 lbs of chainlink fencing, cement, and other materials to job sites. He has 16" Load Range E tires on the trailer and has them pressured to 80 psi, the recommended cold pressure. Hypothetically, once the trailer is unloaded, does he need to be running at 80 psi with an empty trailer ? If he ran the trailer empty at 50 psi, what would be the problem ? since 50 psi can still carry 2600 lbs. What I'm saying is that it's the tire pressure to load ratio that is important, if he ran 3400 lbs at 50 psi, he'd be under inflated, but running empty at 40 psi I'm sure the trailer would coast along just fine. My opinion.
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Old 10-14-2013, 08:09 AM   #47
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Here is a pretty clear quote from the Goodyear Tire Care publication.

"For an equivalent size, a HIGHER load range tire can always be substituted. For example:
• ST225/75R15 Load Range D Marathon can be substituted for ST225/75R15 Load Range C Marathon.
• Match inflation pressure to load-carrying requirements using load and inflation tables."

So it seems pretty clear that it is ok to run Load Range D tires at Load C pressure. Of course they should then only be loaded to Load C weight. I guess the question still remains as to whether there is any benefit to running Load Range D tires at Load C pressure, vs. just using load range C tires. I still think the Load Range D tires would be tougher and therefore worth the extra $6 per tire.
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Old 10-14-2013, 12:33 PM   #48
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Originally Posted by Windywest View Post
Just curious, what is the actual definition of an under inflated tire ?

In my opinion, it is a tire that doesn't have enough air pressure for the load. If you have Load Range E tires, and a load of 1800 lbs per tire, do you need to pressure them up to be able to carry 2800 lbs ?

I have a friend who owns his own fencing company, he has a tandem axle flatdeck trailer which sometimes carries over 10,000 lbs of chainlink fencing, cement, and other materials to job sites. He has 16" Load Range E tires on the trailer and has them pressured to 80 psi, the recommended cold pressure. Hypothetically, once the trailer is unloaded, does he need to be running at 80 psi with an empty trailer ? If he ran the trailer empty at 50 psi, what would be the problem ? since 50 psi can still carry 2600 lbs. What I'm saying is that it's the tire pressure to load ratio that is important, if he ran 3400 lbs at 50 psi, he'd be under inflated, but running empty at 40 psi I'm sure the trailer would coast along just fine. My opinion.
"Under-inflated" is clearly a pressure lower than required to carry the load. BUT If you can improve other performance characteristics with increasing the inflation the answer gets complex.
If you purchase a performance car you will probably have large tires with recommended inflation that is higher than required to just carry the load. Increased inflation in this application will give you better handling and steering response. On High mpg cars you will see higher inflation not for handling but for improved mileage. I have covered the recommendation for multi-axle trailers to run higher than minimum inflation to lower the "slip angle" the tires go through when turning corners. This lower angle will result in lower internal shear forces that are trying to tear the tire structure apart.
So there is no simple single answer because vehicles need to do more than go in a straight line and carry a load.
"Run Flat" does have a definition for warranty purposes. An inflation 20% lower than specified on the vehicle placard is considered "flat".
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Old 10-14-2013, 12:41 PM   #49
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Originally Posted by gljurczyk View Post
garbonz, you are correct. I read all the debates on this issue. The misleading thing to me is the manufacturer inflation charts. Yet no matter if you run your tires low they will cause you premature failure. My mane reason to move up to to a higher rating was not to be able to overload my axle, but to give me the extra strenght or plys which will take some worry away from me.

snip
You didn't say what you found confusing about the Load/Inflation tables. The intent is to specify a minimum cold inflation to set a tire at to carry a specific load. The tables do not address other performance characteristics such as fuel economy, handling, steering response or ability to resist side loading that is unique to multi axle trailers.

Re extra plies. If you read the sidewall of your tires I think you will see that in most cases you are not getting an increase in the number of sidewall plies. The change might be in the bead area as sometimes the increased inflation requires more bead wire while the rest of the tire is already strong enough to pass the various regulatory tests.
One reason to run a higher Load Range would be to allow you to run higher inflation to give you greater safety factor above the minimum needed to carry the load. Another would be to lower the internal shear forces on multi-axle trailers.
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Old 10-20-2013, 06:38 PM   #50
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i would advise against carlisle tires i up graded to load range e from d on my past unit i blew out 8 with less than 500 miles on them i changed back to load range d good year marthon never had another problem kept the carlisle at max air presure with tire covers at all times
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