It really does come down to, "How far are you going to take this"?
Are you going to buy aluminum billet or rod to make parts? Why not refine your own? Wait, you need a refinery for that. Why not make your own refinery, too? Then, you need ore. You'll have to have your own mine.
If it's steel, you need to mine iron and coal. Who makes the shovels?
You are hung up on the tires because you don't know how they are made. If you knew, they would not be so daunting to you. You need silk or cotton fibers (plantation, seeds, carding machines, spinning wheels), rubber trees, a few more chemicals for additives, tube and tire molds and some ovens.
Get my point?
Our success as a species is due, in part, to our collaboration with others.