Ken wrote:
The PVC is only to build up the circumference of the wheel?
Ken

The PVC serves two purposes. Since the idler center piece is
almost always thinner than the drive wheel the PVC serves as
a backing for rubber tire width. In this case, the original
tire thickness was about 0.150" and the center piece is only
about 0.050" thick. Secondly, the increased surface area allows
a better bond between all the materials. Metal to PVC to Rubber.

One of the problems I've seen with some "rebuilt" idler wheels was
the almost zero width of the replacement tire. Yes it works, but it
is a problem waiting to happen due to the limited contact area between
the capstan (motor shaft) and the idler, allowing for an early failure
due to dimpling when at rest.

And, as they've repeatedly stated in the entire history of auto-
motive racing, "If the rubber don't connect, nothing else matters."

A wider idler tire means better traction to the capstan and the
inside of the turntable platter with a minimum amount of slipping.
The spring tension holding the idler against the capstan and inside
of the turntable is fairly light to avoid the other issue of creating
a dimple while the system is turned off.

Jeff