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Old 02-01-2013, 08:50 PM   #1
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Lt Trailer Tires and Other Tire Info.

After airing up my tires on one of my equipment trailers, and hearing all the, LT tires or not, 65mph rating on SP tires and all that jazz- I noticed my tires were LT 235-85-16 "trailer use only", and this was on my spare too. 2 different brands and 2 different load ratings. One was a 14ply and one 10 ply.


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Old 02-01-2013, 08:52 PM   #2
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Also found this info. Great info from a tire sellers website-
Herk may even want to save this!
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Trailer Tires vs. Passenger Vehicle Tires

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There are differences in the driving requirements between the tires on your trailer and those on the car or light truck you used to tow it. Therefore there are distinct differences between the way trailer tires and tow vehicle tires are engineered.

Your tow vehicle is a leader, which means traction is a key focus in the design of its tires. Traction allows your tow vehicle to accelerate down the road, turn around the corner and brake to a stop. Another important consideration is tow vehicle tires are designed for ride comfort, which is achieved in part by allowing their sidewalls to flex.
Your trailer is a follower, which often makes tire sidewall flexing a negative. Sidewall flexing on trailers, especially those with a high center of gravity (enclosed/travel trailers) or that carry heavy loads, is a primary cause of trailer sway. Typical passenger radial tires with flexible sidewalls can accentuate trailer sway problems. The stiffer sidewalls and higher operating pressures common with Special Trailer (ST) designated tires help reduce trailer sway.

Also consider that Special Trailer (ST), as well as Light Truck (LT) tires are fully rated for trailer applications. This means ST- and LT-sized tires can carry the full weight rating branded on the sidewalls when used on a trailer.

However when P-metric or Euro-metric tires are used on a trailer, the load capacity branded on the sidewalls must be reduced by 9%. This means P-metric or Euro-metric tires with a maximum branded load rating of 1,874 lbs. for use on a car is only rated to carry 1,705 lbs. when used on a trailer.

Comparing the load capacities of a pair of tires of the same dimensions fitted to a single axle trailer,*ST225/75R15*Load Range C-sized tires inflated to their maximum of 50 psi provide 4,300 lbs. of load capacity, where*P225/75R15*Standard Load-sized tires inflated to their maximum of 35 psi would be limited to 3,410 lbs. of load capacity, a total reduction of 890 pounds.
Trailers will be more stable and pull better on tires designed specifically for trailer use. Since Special Trailer (ST) tires are constructed with heavier duty materials, they are tougher than typical passenger vehicle tires. This is a plus because trailer suspension systems are generally stiffer and less sophisticated than automotive suspension systems.

Special Trailer (ST) Tire Speed Ratings
Industry standards dictate tires with the ST designation are speed rated to 65 MPH (104 km/h) under normal inflation and load conditions.

-However industry standards also stipulate, if tires with the ST designation are used at speeds between 66 and 75 mph (106 and 121 km/h), it is necessary to increase their cold inflation pressure by 10 psi (69 kPa) above the recommended pressure for the rated maximum load.
Do not exceed the wheel’s maximum rated pressure. If the maximum pressure for the wheel prohibits the increase of air pressure, then maximum speed must be restricted to 65 mph (104 km/h).
The cold inflation pressure must not exceed 10 psi (69 kPa) beyond the inflation specified for the maximum load of the tire.
Increasing the inflation pressure by 10 psi (69 kPa) does not provide any additional load carrying capacity.
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Old 12-20-2013, 10:25 AM   #3
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http://www.tirerack.com/tires/tirete...jsp?techid=219

Found the Correct Link to the original information.
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Old 12-20-2013, 10:57 AM   #4
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Quote:
Originally Posted by herk7769 View Post
http://www.tirerack.com/tires/tirete...jsp?techid=219

Found the Correct Link to the original information.
I understand what they said. The major factor that is missing is the rim rating. I just installed 4 new stems for my TST system. I asked the guy to show where the rating was for my rims. My rims are stamped on the back of the spoke which showed 2160 lbs. According to the HTW site the rim manufacturer. The load rating corresponds to 60 lbs. PSI, thats max the rims can hold which is plenty for me being each wheel weight is 1675 lbs. He said to run my tires at max rim rating or 60 lbs PSI. Is this correct. I have read so much on this stuff I'm getting confused and it don't take much to do that. Oh ya the tires are marathon ST d rated. The cp is 65 lbs stamped on the tire.
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Old 12-20-2013, 11:04 AM   #5
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I went from C rated tires to D rated. (50 psi to 65 psi). My rims are rated for 60 psi. So, I play it safe, put 57 psi in my tires cold, and they warm up to about 60 psi once underway.

I can't imagine that these rims are going to come apart. My guess, and it's only a guess, is that the manufacturer is more worried about weight than psi.

I use the TST monitoring system also. Great system.
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Old 12-20-2013, 11:49 AM   #6
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60 PSI in all four tires (rims are also stamped with a weight and not a PSI).

Did notice the front set of tires wearing on the center showing over-inflation but the rear set are evenly worn. Guess the camper is not riding level.

Bought a 3 inch riser for the PullRite Hitch and that should kill 2 birds.
Not only should I ride more level, but I can now use my hard top bed cover again for security unhitched.
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Old 12-20-2013, 11:52 AM   #7
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Quote:
Originally Posted by acadianbob View Post
I went from C rated tires to D rated. (50 psi to 65 psi). My rims are rated for 60 psi. So, I play it safe, put 57 psi in my tires cold, and they warm up to about 60 psi once underway.
My uneducated guess is that the rims are rated for 60psi cold and you shouldn't need to only inflate to 57 psi.

Doubt your hurting anything as long as 57 psi carries the load.
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Old 12-20-2013, 12:18 PM   #8
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My uneducated guess is that the rims are rated for 60psi cold and you shouldn't need to only inflate to 57 psi.

Doubt your hurting anything as long as 57 psi carries the load.
That's how I read it as well. Cold inflation.

PSI can really climb 15-20 PSI depending on outside air temp and road conditions when the tires are hot.

Had the TPMS in the truck howl when the pressure went over 100 PSI (normal 80 cold). The outside air temp was 115 degrees in Texas this summer and the "sunward" rear tire was getting pretty warm.

Since the TPMS in the truck only goes to 2 digits, the system read zero and treated it like it went flat. Scared the (well it sacred me), and I pulled over the first time. When I realized what was going on, I was less concerned.
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Old 12-21-2013, 04:38 AM   #9
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Quote:
Originally Posted by herk7769 View Post
That's how I read it as well. Cold inflation.

PSI can really climb 15-20 PSI depending on outside air temp and road conditions when the tires are hot.

Had the TPMS in the truck howl when the pressure went over 100 PSI (normal 80 cold). The outside air temp was 115 degrees in Texas this summer and the "sunward" rear tire was getting pretty warm.

Since the TPMS in the truck only goes to 2 digits, the system read zero and treated it like it went flat. Scared the (well it sacred me), and I pulled over the first time. When I realized what was going on, I was less concerned.
Whoa, Did not know that the PSI could raise that much from heat, learn something everyday...Thanks for the info. I know the rims can handle more pressure then what they state. I will watch for that on my way to Pensacola NAS in the end of January....
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