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Old 07-03-2013, 07:49 AM   #21
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Updated and corrected information

Some clarifications and comments on statements in this thread from a Tire Engineer.

"An "LT" designation on a trailer tire size specifies load range only. It is not designed for use on light trucks."
Actually the first letters of the tire size indicated the "Type" tire as specified by Tire & Rim Association. P would be for Passenger vehicle service, LT is for Light Truck and ST is Special Trailer. The load formula that generate the numbers in the tables are slightly different for each "Type" tire and is based on the expected service conditions and usage. There is no such designation as an LT tire for trailer application.
"Load Range" is a letter code C, D, E etc that identifies the max inflation for that specific tire. Load Range is molded on the tire sidewall and is at the beginning of the tire size marking.

While vehicle manufacturers can select P tires for a Light Truck application there are adjustments that are required for the load capacity. LT tires may be selected by the manufacturer for use on trailers but the load capacity of the LT type tire must be used not the load capacity for a similar size ST tire.

ST tires are never to be applied on a vehicle intended to carry passengers.

"Always inflate trailer tires to the maximum inflation indicated on the sidewall."
This is correct for trailer application but not always correct for motorized vehicles such as cars, light trucks or motorhomes.

"The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent."
This would be a good guide and I would support this but it is not a requirement

RE Actual weight: Since it is documented that a majority of RVs have one or more tires overloaded, you really need to get your unit on a scale when fully loaded at its heaviest and confirm you are not exceeding the tire or axle or RV max rated capacity. Here is a web site that tells you how to weigh and calculate to learn the actual tire loads.


"In approximately three years, roughly one-third of the tire's strength is gone." I have never seen data that supports this statement. I am also not sure what is meant by "strength" as the tire is designed to contain the air pressure so that would be it's "strength". It is the air pressure that carries the load, not the tire.

"Three to five years is the projected life of a normal trailer tire. It is suggested that trailer tires be replaced after three to four years of service regardless of tread depth or tire appearance."
I agree with these general statements for trailer application but this is based on the fact that trailers place significantly more internal stress on the tire structure due to a number of factors.
1. Tandem axle place high side loading forces on the tire structure as soon as you start turning.
2. Most trailer manufacturers select tires with very little or no margin of safety for load capacity when compared to actual usage
3. Almost all ST type tires are operated for some amount of time at or above their "red line" speed limit of 65mph. This generates excess heat which consumes the tire life at an accelerated rate.

Statements on the ST tire polyester and steel being larger or stronger may or may not be true.The rubber also may or may not contain more weather resistant chemicals. I am not aware of any broad study that would support these claims.

Hope this clears up a few things.
Roger
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Old 07-03-2013, 08:09 AM   #22
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..."Always inflate trailer tires to the maximum inflation indicated on the sidewall."
This is correct for trailer application but not always correct for motorized vehicles such as cars, light trucks or motorhomes...
I agree whole heartedly with the max inflation. Cupping on a tire is caused by an out of balance condition, not over inflation and bouncing. Also inflating to max pressure will not cause the tire to wear in the center on our trailers as the trailers are usually loaded to the mid to upper range of capacity. Finally, the trailer will not ride any harsher on max pressure than with 5# or 10# under the max.
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Old 07-03-2013, 08:33 AM   #23
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Tireman9. Wow. Thanks for the great link to the Fifth Wheel site. I just did a quick glance and then I'm going back for in depth reading. Looks like lots of great info.
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Old 08-19-2013, 05:20 PM   #24
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New Tire question/problem. We have a 2011 FR Wildwood. These are the original factory tires. We average about 6500 to 7000lb depending on how many days we're planning to be out. I noticed after we came back this Sunday from a long weekend, the driver side rear tire on the tandem set up was wearing badly on the outside edge. The front tire looked really good. The two tires on the other side were wearing evenly, somewhere between the wear of the two on the driver's side. I also notice really dark tire marks on the driveway after we back in. Checked all tire pressures at 50#. We keep covers on the tires when we're parked. Can there be an alignment or some other adjustment issue that needs to be checked? Rotate the tires front to back?
Thanks for any suggestions and feedback
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Old 08-19-2013, 05:48 PM   #25
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New Tire question/problem. We have a 2011 FR Wildwood. These are the original factory tires. We average about 6500 to 7000lb depending on how many days we're planning to be out. I noticed after we came back this Sunday from a long weekend, the driver side rear tire on the tandem set up was wearing badly on the outside edge. The front tire looked really good. The two tires on the other side were wearing evenly, somewhere between the wear of the two on the driver's side. I also notice really dark tire marks on the driveway after we back in. Checked all tire pressures at 50#. We keep covers on the tires when we're parked. Can there be an alignment or some other adjustment issue that needs to be checked? Rotate the tires front to back?
Thanks for any suggestions and feedback
Definitely sounds like an axle alignment problem. Do the driveway marks match up with the worn tire position - if so I would strongly suspect alignment problems.

I wouldn't rotate any tires until the alignment is checked and necessary repairs are made.
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Old 08-19-2013, 05:52 PM   #26
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New Tire question/problem. We have a 2011 FR Wildwood. These are the original factory tires. We average about 6500 to 7000lb depending on how many days we're planning to be out. I noticed after we came back this Sunday from a long weekend, the driver side rear tire on the tandem set up was wearing badly on the outside edge. The front tire looked really good. The two tires on the other side were wearing evenly, somewhere between the wear of the two on the driver's side. I also notice really dark tire marks on the driveway after we back in. Checked all tire pressures at 50#. We keep covers on the tires when we're parked. Can there be an alignment or some other adjustment issue that needs to be checked? Rotate the tires front to back?
Thanks for any suggestions and feedback
Sounds like a bent spindle if the other 3 tires are wearing evenly or if the 2 driverside tires are wearing, you may have 2 bent spindles.
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Old 08-19-2013, 05:55 PM   #27
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Thanks Coot
Something that can be checked at a regular tire shop or does it need to be looked at by an RV specialist?
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Old 08-19-2013, 06:03 PM   #28
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Thanks Coot
Something that can be checked at a regular tire shop or does it need to be looked at by an RV specialist?
Doubt if a tire shop could or an rv specialist, but a trailer alignment shop sure could. I would venture a guess it is either toed in or the camber is off if it is wearing on the outside. You could get an idea about toe in by laying a straight edge across both tires and seeing if it touches both tires in two places and placing a square on a level surface and seeing if it measures the same from the square to the edge of the rim at top and bottom.
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Old 08-19-2013, 06:24 PM   #29
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TRailer alignment shop? Didn't know such places existed.
Will do the suggested checks tonight and quick search for an alignment shop as well.
No indication on the rim or hub that there has been any trauma. Could it have sipped that way?
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Old 08-19-2013, 06:28 PM   #30
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TRailer alignment shop? Didn't know such places existed.
Will do the suggested checks tonight and quick search for an alignment shop as well.
No indication on the rim or hub that there has been any trauma. Could it have sipped that way?
Look for over the road trailer shops.

What area are you in?
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