I picked up what I thought was a pair of Bolens cast rims. As I was loading them, I noticed they weren't quite a pair. The offset was different between the two rims. The seller said they both came of the same tractor. Were these rims all made with a different offset for clearance on one side or another? I only see one number cast on one half of one wheel although all 4 castings are different. Any thoughts? I don't see where anyone else has mentioned this.