15x4, [or maybe it was 4 1/2] was factory A100 wheel size. well, i should say there were 2 on my brother's '69 A100. those had the large [62-66] center bumps for the dog dish caps. 50's studebaker wheels were 15x4 with the 4 1/2" bolt pattern and took the small center dog dish caps. i have 3 chromed ones on the shelf waiting use on an upcoming project.