Welcome to the forum Steve.
I have at least one tractor tire, some semi tires and also car tires in tee-pee fashion and also in conjunction with concrete foundation pieces. Far as I know they work ok. I have went down with scuba gear and checked on them. Still there.
I do have CC recruitment so they could be using the tires for cavities to spawn in.
You might try the structure archives.
Structure archives here Unfortunately because of a change in Photobucket, a lot of the pictures will not be view-able unless you have a patch for your browser to get around the link problem.
