Boat Trailer Tire Rot

[XCR-700]

This issue may have been addressed previously but I'd like to hear some current thoughts.

The issue is tire rot.

What causes it and is it covered by the manufacturers warranty?

I have read opinions that say tire rot is caused by exposure to sunlight, or lack of use, or by submersion in saltwater but in my case I have 2 boats that have matching spares and the tires on the axle/ground seem to exhibit rot much faster than the spares. And the ones on the axle/ground are usually covered by the tarps I have on boats and the spares are not, they are exposed to sunlight, and have never been in saltwater!

I’m really at a loss to understand how trailer tires can rot so quickly, especially since I have an original spare tire/rim from my 1977 Chrysler Cordoba that has NO rot! And its been sitting outside for the last 10 years!!!

Whats wrong with this picture?

And looking at the manufacturers warranty language its not clear to me that rot is either covered or not covered,,,

What is the current thoughts around trailer tire rot?

Thanks