powerboatr
living well in Texas
they make trailer tires for a reasonLT tires are not designed for the long term side loading a "swaying" trailer generates going down the road. they will run hotter than they are designed to, and prematurely fail. In a picnh or as a spare, maybe - but I will never run a car or truck tire on a trailer of anysort.
Instead of buying another set of tires for storage, just put hte trailer up on jackstands
sorry thats just not true....
LT tires like to be rolled on not sat on...10 ply tires hold up to sidewall loads better than st tires.
both my last tow rvs came with LT tires ????
st tires have a thicker ozone protection layer built in to aid in longevity when stored and not rolled on.
i agree however iffin your storing it.....use some old cheapie till its time to roll then put on a good new set
but hey its my dime
Trailer Tire Applications
Trailer tires are designed for use on trailer axle positions only, not for the loads applied to or the traction required by drive or steering axles.
An "LT" designation on a trailer tire size specifies load range only. It is not designed for use on light trucks.
Do not mount "ST" or "LT" trailer tires on passenger cars or light trucks.
Inflation
Always inflate trailer tires to the maximum inflation indicated on the sidewall.
Check inflation when the tires are cool and have not been exposed to the sun.
If the tires are hot to the touch from operation, add 3 psi to the max inflation.
Underinflation is the number 1 cause of trailer tire failure.
Load Carrying Capacity
All tires must be identical in size for the tires to properly manage the weight of the trailer.
The combined capacity of the tires must equal or exceed the GVW of the axle.
The combined capacity of all of the tires should exceed the loaded trailer weight by 20 percent.
If the actual weight is not available, use the trailer GVW. If a tire fails on a tandem axle trailer, you should replace both tires on that side. The remaining tire was likely subjected to excessive loading.
If the tires are replaced with tires of larger diameter, the tongue height may need to be adjusted to maintain proper weight distribution.
Speed
All "ST" tires have a maximum speed rating of 65 mph.
As heat builds up, the tire's structure starts to disintegrate and weaken.
The load carrying capacity gradually decreases as the heat and stresses generated by higher speed increases.
Time
Time and the elements weaken a trailer tire.
In about 3 years roughly one third of the tire's strength is gone.
Three to five years is the projected life of a normal trailer tire.
It is suggested that trailer tires be replaced after 3 to 4 years of service regardless of tread depth or tire appearance.
Mileage
Trailer tires are not designed to wear out.
The life of a trailer tire is limited by time and duty cycles.
The mileage expectation of a trailer tire would be 5,000 to 12,000 miles.
Why Use An "ST" Tire
"ST" tires feature materials and construction to meet the higher load requirements and demands of trailering.
The polyester cords are bigger than they would be for a comparable "P" or "LT" tire.
The steel cords have a larger diameter and greater tensile strength to meet the additional load requirements.
"ST" tire rubber compounds contain more chemicals to resist weather and ozone cracking.
Storage
The ideal storage is in a cool, dark garage at maximum inflation.
Use tire covers to protect the tires from direct sunlight.
Use thin plywood sections between the tire and the pavement.
For long term storage: Put the trailer on blocks to take the weight off the tires, lower the air pressure and cover tires to protect from direct sunlight.
Maintenance
Clean the tires using mild soap and water.
Do not use tire-care products containing alcohol or petroleum distillates.
Inspect for any cuts, snags, bulges or punctures.
Check the inflation before towing and again before the return trip.
Three Keys to Avoiding Trouble
Make sure your rig is equipped with the proper tires.
Maintain the tires meticulously.
Replace trailer tires every three to five years, whether they look like they're worn out or not.
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Ever thought about the fact that some of us might be members over there too? Maybe take a clue from some of our signatures 
I'm sorry, but you could have given a 'better' answer such as this: "Although there is some great information given here, you may want to try RV.NET (or other sources) too, they have a forum totally dedicated to this subject." Nothing against you either. 
subscribing