and now my first wheels question

thanks everyone
i pulled the rear wheels off and there is a 5/16 inch spacer plate welded on each wheel. i'll take a pic tonight and post it so you can see what i am referring to. not just a normal wheel spacer as it has been cut and bent to match the contour of the hub. these spacers are NOT on the front and i am wondering if that is the issue.

thank you again everyone.