Rims are measured where the bead of the tire sits so if you're measuring from outside edge to outside edge and get 16.5”, it’s most likely a 15” rim.

Here is a photo of a 15” rim and it measures 16.5” outside edge to outside edge. Please note the picture make it look like I didn't have the ruler centered on the rim, but it was and it’s just an illusion.
Attachments
IMG_3629.jpeg (193.07 KB, 45 downloads)
Measuring a 15” rim.

Last edited by Phak1; 08/18/2024 12:27 PM.

Phil
Moderator, The Engine Shop, Interiors and Project Journals

1952 Chevrolet 3100, Three on the Tree, 4:11 torque tube
Updated to: ‘59 235 w/hydraulic lifters, 12v w/alternator, HEI, PCV and Power front Disc Brakes
Project Journals
Stovebolt Gallery Forum