Interesting idea.  If the tire is UVmapped properly, it should be possible to do this with a single map.  You'd have a static bump map of the tread itself, then blend it with a negative displacement map.  Animation would simply move the U offset of the negative displacement.

A python script would then determine which part of the tire is currently down,
and adjust the U offset accordingly.  (This would require a pre-measured
correlation between the offset and the rotation angle of the wheel.)

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