what would possibly exist in the farthest east?

[Zigûr]

Originally Posted by Rune Son of Bjarne

I guess that would be true if the Gondorians had previously been using chariots, and these had become obsolete. However this does not seem to be the case...

Does this necessarily follow? The Men of the West certainly used wheeled, horse-drawn vehicles in general. They evidently knew what chariots were by observation even if they didn't use them. I don't see the use of chariots in particular as some kind of 'necessary' step in the technological progress of a society, ie "the Men of the West did not use chariots therefore they were more primitive than the Easterlings."

Frodo himself upon Amon Hen observed the Easterlings as having "swordsmen, spearmen, bowmen upon horses, chariots of chieftains and laden wains" (emphasis mine) which suggests to me that even Easterling chariots were more commonly used for ceremonial purposes and as transportation than as weapons.