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PostPosted: Mon Jul 27, 2015 7:42 am 
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Location: Delnor Wiggins, Fl Peters Twp PA
I've got a Trailex SUT 350 for our TI. It has the standard 4.80 x 8 bias tires. The sticker on the tongue says that the recommended tire pressure is 20 PSI while the sidewall max pressure is 90 psi. The dealer had them at 45. I called Trailex to confirm that the sticker was correct and they confirmed it. I'm going to be putting 1200 highway miles on the rig soon and want to make sure that I have it set up properly.

What PSI do you folks generally use for your trailer tire pressure?

Thanks for your help!


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PostPosted: Mon Jul 27, 2015 7:51 am 
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I put in whatever the sidewall pressure says. I haul my AI(s) about 1000 mi per year at expressway speeds on my Trailex trailer.

Keith

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PostPosted: Mon Jul 27, 2015 9:09 am 
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The information on the tire is the maximum. The manufacturer normally does not make a tire for a specific application. It is up to the engineer that designs whatever the tire will be used for to determine the correction pressure for that particular application. As long as the specified pressure falls in the range that the tire manufacturer states, all is good. Look at your car tires then look at what the car manufactuer recommends...almost certainly different figures.

Honestly, I never paid any attention to the sticker before. I have run 15 PSI in mine for 3 years without problem and I have the extra weight of a PVC mast carrier on mine. I found that higher pressure made for a rougher ride with more vibration. I also had my tires high speed balanced.


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PostPosted: Mon Jul 27, 2015 11:12 am 
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Location: Delnor Wiggins, Fl Peters Twp PA
Thanks, gents. It looks like anything will be okay - not too surprised given the very light load. I appreciate the help.


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PostPosted: Mon Jul 27, 2015 12:09 pm 
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Too much initial pressure and you end up higher when heated.

Too much pressure and you get a bouncy ride.

Same as my truck. The max pressure is WAY higher than the truck manufacturer suggests (by almost double).

I would do what Trailex suggests. Check tire heat from time to time.

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PostPosted: Mon Jul 27, 2015 3:09 pm 
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Location: Austin Texas
Trailer tires are supposed to be inflated when cold to the pressure shown on the sidewall. Not to a pressure adjusted for the load on the tire. The tire is selected for the load then inflated to the sidewall pressure.
Here's some trailer tire care information:
http://www.carlisletransportationproduc ... ctices.pdf

Chris


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PostPosted: Mon Jul 27, 2015 5:46 pm 
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I put 30 psi in my 8" Trailex Tyres to get a nice firm seal on the rim. I have found 20 psi in the past allows the tires to slowly deflate. There isn't much load so there is no reason to over inflate.


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PostPosted: Mon Jul 27, 2015 7:50 pm 
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I agree 100% with Buckaroo. I've been designing trailers for 27 yards and every single tire failure (other than road hazard or wore out tires) is due to underinflation. I am really surprise that Trailex would tell you to use such a low pressure. This causes the tires to heat up at highway speeds and the tread eventually separates from the belts, whether bias or radial. The effects are much more radical with bias tires as they do not dissipate heat as well as the radial design. I've seen tires returned to me with only the sidewalls on the rim. Over and over, I hear the same thing. "I run my tires soft fur a better ride". The suspension is designed to provide the "ride" on trailers. Automobiles are a totally different story. A hot tire is also detrimental to the grease in the hubs. My advice concerning a trailer: maximum inflation.


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PostPosted: Tue Jul 28, 2015 7:10 am 
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Location: Delnor Wiggins, Fl Peters Twp PA
Yes, I was surprised that the Trailex sticker had such a low pressure on it. I was doubly surprised (shocked) when they said, "No that isn't a mistake. Use 20 psi."

At the same time, it has also been my experience that the Max Pressure Rating on a tire's sidewall is NOT the suggested inflation point - it's the fail point. Hence my befuddlement.

FWIW, I'm starting at 45 psi. If the trailer is ill behaved, I'll drop it. Generally, my car tires gain 4 - 6 lbs from cold to hot. I'm guessing that trailer tires will be similar. I did pick up a spare air pump last night just in case...If you see a guy on the side of the road with a Hobie tarp on his TI, throw him a cookie, pls..

Thanks again.


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PostPosted: Tue Jul 28, 2015 9:35 am 
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Lots of disagreement on what the tire pressures should be here.

I strongly disagree with using the max pressure as the standard. Completely contrary to my understanding of tires and how they wear. I believe you can find anything you want to online to support an argument, but when a vehicle manufacturer tells you what is recommended... that is what they designed for their product. Most tires are not specifically designed for a vehicle, They are selected as a good fit for the load and function of the vehicle.

Tires have a much higher maximum pressure than is realistic in most conditions. Max pressure is typically for max load. Premature wear and poor handling are things I have experienced personally from over or under pressure.

Here is a guide that makes better sense to me:

Quote:
THE MAXIMUM

Somewhere on the sidewall of your tire, just below the big, bold letters of the manufacturer, for example, you might have noticed the words ‘Max. Press. 35 PSI.’ That number tells you the maximum cold pressure needed for your tire to carry its maximum load.

We mention ‘cold’ pressure because that means you’re filling up your tires at the ideal time—when they’re cold. First thing in the morning or after sitting for a few hours in the shade is best.

Usually, your tire’s maximum tire pressure is somewhere between 30 and 32 PSI.

What happens if you inflate your tires to the max PSI?

The handling characteristics change
Since tires inflated to the max can’t give as much on the sidewall, you might see superior cornering, but it could be at the risk of your braking threshold. One quick corner and your back end could slide out.
The life of your tire decreases. When your tires are inflated too much, the rubber rounds out at the top of the tire when you’re driving, and the center will quickly wear out. You’ll also reduce your traction and you could even cause a blowout. Check out our post on avoiding blowouts.
So, what’s the right tire pressure for your vehicle?

THE OPTIMUM

You’ll find the manufacturer’s optimum or recommended tire pressure for your car on a sticker in the door jam, or in your owner’s manual. Some models even place the stickers on the trunk lid, in the console or on the fuel door.

Recommended pressure is usually between 30 and 35 PSI. That number indicates the minimum amount of air pressure needed to support your vehicle’s maximum load-carrying capacity. Any less, and you’ll see poor fuel economy and handling as well as premature wear from too much flexing and tire overloading.

When your tires are inflated to the recommended PSI, you enjoy their optimum life and performance.

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Matt Miller
Director of Parts and Accessory Sales
Hobie Cat USA


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PostPosted: Tue Jul 28, 2015 1:32 pm 
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Location: Austin Texas
Matt, that information is for passenger car tires.
Sometimes people put vehicle tires on a trailer ( and shouldn't ), but that is the only time you would put such a low pressure in a tire that is on a trailer.
An additional note from personal experience is to pay attention to the DOT date code on tires if you buy a used trailer. Tires that look perfectly serviceable but have exceeded their service life time wise may (will) fall apart at the worst possible time.
The link I posted above is from Carlisle, a major manufacturer of trailer tires.
More info from etrailer.com :

Special Trailer (ST) Tires and Air Pressure

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.




Speed Rating of ST Tires

Special trailer tires are usually rated to operate at a maximum speed of 65 mph. If you exceed 65 mph, heat could build up in the tire and cause it to break down and fail. If a tire is rated to run at a higher speed, this information should be listed on the tire's sidewall.




Matching ST Tires

You should always use tires of the same size, load range, and construction on a trailer. If you use tires that don't match, you could experience problems of overloading and overheating, which can lead to tire failure.




Radial Trailer Tires vs. Bias Ply Trailer Tires

The main difference between a radial ply and a bias ply tire is how the tire is constructed. The cords inside a bias ply tire run at a 32 degree angle to the direction of travel, and the cords on a radial tire run at a 90 degree angle to the direction of travel, or across the tire from wheel lip to wheel lip.

A radial tire flexes more than a bias tire, giving it better ground contact, traction, stability, and tread wear.

A radial tire will normally run cooler than a bias ply tire, especially when the tire is under a load. A tire that runs cooler will last longer.

A bias ply tire has a stiffer sidewall than a radial, a feature that might be useful for off road applications like farm use.

At one time radials were more expensive than bias ply tires, but now they are closer in price. This makes radials a much better value.




DOT Tire ID Number

The Department of Transportation (DOT) identification number code is stamped on one side of the tire, near the bead. The code starts with the letters "DOT", then has two numbers or letters to identify where the tire was manufactured. The last four numbers represent the week and year the tire was built. For example, the number 0410 means the fourth week of 2010.




Tire Balancing

At etrailer.com, our tire and wheel combinations are mounted so that the high heavy spot on the tire is aligned with the low light spot on the wheel. This provides adequate balance for trailer tires.

If you buy new tires for a set of rims, you can have them balanced. If you do balance trailer tires, remember that many trailer wheels are centered by the position of the lug bolts (these wheels are lug-centric) and not the center bore of the wheel. To get the best tire balance for lug-centric wheels, you should have them balanced using a pin plate adapter. This mimics the way a lug-centric wheel is mounted to a hub.




Determining Wheel Offset

Wheel offset refers to the location of a wheel's rim in relation to the wheel's center. The rim can be centered on the wheel or it can be offset to either side. The position of the rim determines where the tire lines up - either closer to or farther from the vehicle or trailer on which it is mounted. Trailer wheels usually have zero offset, meaning that the rim of a trailer wheel lines up directly under the center of the wheel. This alignment puts the tire directly under the center of the wheel, giving the wheel and tire combination the greatest ability to handle load.

To determine if your trailer wheels have an offset, remove a wheel from your trailer and measure from the mounting surface of the wheel (where the wheel mounts to the hub) to the inside and outside beads. The difference between these two measurements is the offset.

Because some trailer wheel offsets can be as small as 5 mm, they can be difficult to measure. If you can't measure the wheel, contact your trailer manufacturer with your trailer's serial number.


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PostPosted: Tue Jul 28, 2015 2:49 pm 
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Buckaroo wrote:
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. (admin: describing best wear for max load and pressure)

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. (admin: this describes what Trailex recomends... due to the very light weight trailers and loads) 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. (admin: agreed... heavier loads require more pressure)

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.

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Matt Miller
Director of Parts and Accessory Sales
Hobie Cat USA


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PostPosted: Tue Jul 28, 2015 3:08 pm 
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We do a lot of trailering, with our campers and such, as well as our boat trailer. Trailer tires are a different type of tire design from passenger tires, the reason car makers underinflate the cars tires is to improve ride only, at the detriment of the tires themselves, always go by the tire manufacturers recommendations (not the automaker).
Buckaroo is absolutely correct in everything he is stating. All trailer tires need to be inflated close to the rated inflation marked on the tire.
Bob


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PostPosted: Tue Jul 28, 2015 3:56 pm 
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I'm very surprised that Trailex would recommend something that would not be best for their product (liability), so I will give them a call tomorrow to verify.

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Hobie Cat USA


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PostPosted: Tue Jul 28, 2015 5:27 pm 
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I'd err on the side of a little too much rather than a tad too little.

Watch the wear pattern on the tread of the tire. If it's wearing on both outsides, run a little more air. If it's wearing mostly on the center, run a little less.

I run 25PSI in the tires on my Trailex. I did swap to a larger diameter 8 inch tire to make things easier on the hubs and bearings at highway speeds.


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