A picture of a tiger tank in tunisa was just put up in the "I pwn you" thread and I noticed that the roadwheels are right up against the edge of the tracks. I've seen some diagrams that have this extra set of wheels but I don't think many of the later tigers had them Compare this With this
The first picture is of an early model Tiger I and the second picture is of a late model. The late model had different types of road wheels. In the late model the outside run of wheels was left out, so indeed it misses a set of wheels.
One thing you might also want to note is that there are 2 types of tracks on the Tiger I, the 520mm transportation tracks (for on railway cars) and the 725mm combat tracks. Though both the tanks in your pictures are fitted with the wide combat tracks.
I dare say the automotive aspects of tanks is quite complex!
IIRC the early wheels pictured are rubber rimmed and the late model has steel rimmed road wheels due to scarcity of rubber.