i saw a product in a magazine for a hubcap of sorts that you can put over your rims while applying tire shine to keep it from getting all over the wheel, and i decided to make my own

i was measuring for a template when i noticed that from edge to edge my "18 inch wheel" is actually 19.5 across haha. i have the supposedly 18 inch ford 5 spoke wheels from 2010 and up gt's

any ideas? im guessing its just measured somewhere else on the rim? i dont know why it would be though...

 

oh and heres a picture i forgot to upload on the first post

 

18" is the diameter of the tire opening