Sorry about contributing to the thread drift but this exchange about the tires themselves is interesting and useful...

When I changed the tires on my Cobra trailer about 6 years ago (yeah, I'm due) I purchased trailer tires that were already mounted on wheels. When putting the tires onto the trailer the tires ended up sticking out a few inches from the fenders. That's when I noticed that the original Cobra wheel had a positive mounting offset while the new wheels had a zero offset. I decided to mount the new tires onto the old wheels. I've not had any problems so far but wondering about the criticality of the wheel mounting offset especially as I go shopping for new tires for the upcoming season.

From the etrailer.com website:
Trailer or automotive wheels can have a positive or negative offset. The offset refers to the distance between the mounting surface of the wheel that touches the hub and the center line of the wheel...
A positive offset will move the tire closer to the trailer, while a negative offset will push the tire further away.
Most of the trailer wheels we offer, including the Americana Aluminum Mod wheel you referenced, part # AM22327, have a zero offset, which means that the the mounting surface is on the same plane as the center line of the wheel. This is done to equalize the weight of the trailer load.

https://www.etrailer.com/question-44405.html

Danny Brotto