This was my first attempt at welding and fabricating in general. DEFINITELY not hard to do.
I only have the four spares, so one rack is fine.
You COULD do the same thing with 2x4's if you made a support from underneath and maybe built some shelves under the tire rack portion.... that would hold 16 tires without issue. Suspending them all from the wall on one rack may be too heavy for the span...