jaybird, first off, you don't say what brand and age they were. Even if OEM, they probably were at minimum another year older than your rig.
Second, it shouldn't matter one bit that you kept your rig on cement over the winter. This 'tire salesman myth' has been proven false several times over (unless they were made 80 years ago). Whoever told you that was just trying to sell four instead of one.
Finally, you don't say what they sold you for $800. Did you even check the DOT 'born on' dates?
There are hundreds of posts about tires on this Forum and just about every other one I've seen pertaining to 5th wheel trailers. They all pretty much say the same things: Made in China ST tires are junk for heavy weight trailers. ALWAYS check the date codes and don't trust tires over five years old. Good ST and good LT tires work equally well if you pay attention to ratings and age.
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