trailer tires

Thalasso

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Simply because of no shocks on trailer. If trailer had shocks there would be no difference.....LT tire could care less whether it was on a truck or trailer.

That's a good and maybe the right answer but i doubt it's the real reason the DOT made the law
 

bruceb58

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An LT tire has already been derated compared to the equivalent sized P sized tire which is why it doesn't need to be further derated for trailer use.

Problem with switching to an LT tire from an ST is that often it is difficult to get enough capacity switching to an LT tire. On my trailer, I had 14" tires. There were no LT tires available in 14" that had enough capacity to match what I had in an ST tire.
 

Thalasso

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Just looked at all the DOT regs and they don't say why they do the derating at all.

[FONT=&quot]FMVSS No. 120 also contains a requirement related to the use of passenger car tires on vehicles other than passenger cars. The requirement states that when a tire that is subject to FMVSS No. 109 is installed on a multipurpose passenger vehicle, truck, bus, or trailer, the tire's load rating must be reduced by a factor of 1.10 by dividing by 1.10 before determining whether the tires on an axle are adequate for the GAWR. This 10 percent de-rating of P-metric tires provides a greater load reserve when these tires are installed on vehicles other than passenger cars. The reduction in the load rating is intended to provide a safety margin for the generally harsher treatment, such as heavier loading and possible off-road use, that passenger car tires receive when installed on a MPV, truck, bus or trailer, instead of on a passenger car.[/FONT]
 

bajaunderground

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I'm confused, a bit (nothing new). Based off both charts you listed the links to Bruce, as the pressure increases, the load capacity increases, Obviously there's a pressure limit to the tire? For example my Yukon 2500 has pressures listed as 50psi (front) and 80psi (rear) when towing at the capacity based of my motor (8.1L) and gearing (4.10's). I cannot tow with the rear tires at 80psi as it makes my rear end greasy, very greasy. Dropped back down to 50psi and it tows very stable...

So...are the pressures in the charts merely for comparison and not actual tire recommended running tire pressures? Or if your load is higher you should have a rated tire for the higher pressures?
 

bruceb58

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So...are the pressures in the charts merely for comparison and not actual tire recommended running tire pressures? Or if your load is higher you should have a rated tire for the higher pressures?
They are the recommended pressures. Within the chart it shows the limit for each load range within a given size.

As you can see, a load range C has a lower pressure limit than a load range D.

If you were running Load range Cs for a given weight and you switched to Load range D, you would use exact same PSI even though the max PSI of the Load range D was higher.
 

bigdee

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Quoted from etrailer.com [h=2]Special Trailer (ST) Tires and Air Pressure[/h] Some tires are specially designed to be used on trailers. These tires include the letters "ST" in the size specification that is listed on the sidewall. The "ST" stands for "special trailer". This kind of tire has a stronger sidewall than an automobile or truck tire so it can handle higher air pressures and higher loads.
Special trailer tires should be inflated to their maximum air pressure. The value for the maximum air pressure should be listed along with the value for the maximum load on the tire's sidewall. These values will usually designate the maximum load at a maximum psi. For example, if the tire is rated at 1,610 lbs maximum at 65 psi, the tire can carry 1,610 lbs of weight if the air pressure is at the maximum of 65 psi. At the maximum air pressure, the tires will perform and wear best, and get the best gas mileage.
If a trailer tire is inflated to a lower air pressure than the maximum, the amount of weight that the tire can carry will be reduced. If a heavier load is put on the trailer tire than what is recommended for that air pressure, the sidewall of the tire could heat up and cause the tire to fail.
You should always inflate your tires when they are cold.
If a tire is over-inflated, it will wear more in the center of the tread, all the way around the tire. If a tire is under-inflated, it will wear on the outside edges of the tread, all the way around the tire.
 

Thalasso

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I saw all of that. Didn't go into specifics like Bigdee said.

Apparently it's more about provideing [FONT=&quot]a safety margin for the generally harsher treatment, such as heavier loading and possible off-road use[FONT=&quot]. Nothing about shock [/FONT][/FONT]absorbers
 

bruceb58

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Apparently it's more about provideing [FONT=&quot]a safety margin for the generally harsher treatment, such as heavier loading and possible off-road use[FONT=&quot]. Nothing about shock [/FONT][/FONT]absorbers
Totally agree.
 

bigdee

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Shocks do reduce tire wear, frame component stress and TIRE stress. Many larger trailers have them. In my 70 years I have seen and owned construction trailers that ran passenger car tires without issue. In fact the failures I've seen have most always been on boat trailers with trailer tires! Probably from age and under-inflation.
 

On Holiday

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I am running with Carlisle tires and they have been great. I keep the psi up at 50 and keep the speed between 60 and 65. Speed and underinflated tires will kill them. My boat is stored inside a garage when not in use so UV isn't much of a factor. I also rotate the tires once a year as the right front tire does more scrubbing getting into and out of my driveway.
 

vans

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I am running with Carlisle tires and they have been great. I keep the psi up at 50 and keep the speed between 60 and 65. Speed and underinflated tires will kill them. My boat is stored inside a garage when not in use so UV isn't much of a factor. I also rotate the tires once a year as the right https://www.amazon.com/gp/product/B000M8IHI2/ref=oh_aui_search_detailpage?ie=UTF8&psc=1front tire does more scrubbing getting into and out of my driveway.
Long time marathon guy, owned many sets, went to Carlisle a couple years ago and so far it's been good, I pull boat 125 miles one way often, I'm anal about tire pressure and bearing temps, plus the local tire shop carries them, I live in rural area and like to shop locally
 

David Young

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Carlisle has a factory (one of several in America) 2 miles from my house. They used to be called Armstrong tire around 30 years ago until Carlisle bought them out. I have Armstrong tires on my boat trailer, they have to be very old :(. I'm replacing them this spring :)
 

Silvertip

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Although you paid for what you thought were new tires, chances are they were already a couple years old before being sold. Check the date code on the tires. No!~ you don't underflate tires when you are already at or over the capacity for a single axle trailer. Don't forget, the trailer counts as weight also, not just the boat. I bought a brand new pontoon and trailer and the next spring I noticed cracking in the tread grooves. Checking the date code showed the tires were four years old. Yes -- they were replaced free. Blowing that many tires says there is a trailer weight issue. Load range E in the chubby 10 inch size do indeed carry 90 PSI. Pump them up to the max as indicated on the sidewall and you've done as much as you can to resolve the issue. If you continue to blow tires, lighten the load, slow down, and/or buy a new trailer that can handle the load. But under inflation is the primary cause of trailer tire failure, especially if you are at the maximum capacity of the tires.
 

floater212

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Nov 27, 2013
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from what I've been researching.... #1. even slightly under inflation = BAD THING HAPPENING! ( KEEP TIRES AT RECOMMENDED PRESSURE) #2 with terrible highway roads at speed = BAD THINGS #3 even great tires will die from potholes at 65mph no matter how good you are at trying to avoid them, you ultimately still hit some holes. so when the dealer decides which trailer goes with which boat, it does not always make a good match... the trailmaster trailer, Heavy Single, should have been a dual axle!!!
 
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