The archaeologist, David W. Anthony says:
"there is no shared IE root term for the word "spoke".... While the
speakers of PIE shared a set of common terms for wheel (presumably a
solid wheel, as in the earliest European examples), axle, thill, and
wagon, they apparently did not have a term for spoke, arguably
because spoked wheels were invented after the PIE dispersal."
The Archaeology of IE Origins, JIES, p 201, vol. 19, #3&4, 1991
But the Indologist, Michael Witzel says:
"ยง14. Date of Indo-Aryan innovations
....
On the other hand, there are common PIE words for the cart or four-
wheeled wagon
(anas) and its constituent parts, such as and akSa 'axle', ara 'spoke,
pin', nabhya 'nave', yuga 'yoke', razmi, razanA 'reigns', etc.; for
details
see EWA, s.v. They are much older, PIE, as they refer to the more
primitive technology of solid wheel wagons and carts that was
developed in
Mesopotamian in the late 4th millennium."
http://www1.shore.net/~india/ejvs/issues.html
Since he later ties spoked wheels to the Indo-Aryans and uses it as
one of the main reasons why India is not the home of the Inde-
Europeans, I'm wondering if anyone has any comments about this
discrepency. It looks as if the PIEs had chariots but not spoked
wheels which were a later development so the presence of spokes is
not germane to the Indo-Aryan question.