Ok, folks I managed to have this working... partially:
I am using the loopOut("offset") on each wheel's rotation property with two keyframes set at the beginning and end of time (0 degrees and 359 respectively).
The problem is that the wheel that should actually follow the logical group movement is not spinning if I set a negative rotation degree on the end keyframe.
All the others are spinning happily but... in the wrong direction.
I am subcomping the group of three wheels, and then each wheel separately.
One interesting aspect is that in the wheels group subcomp the problem wheel is spinning just fine.
It's in the main comp where I use loopOut("offset") on the wheels group subcomp rotation the problem wheel with the negative rotation is stuck.
I am a bit unsure as to why you are pre-compositing your elements. This should be quite straightforward: import ai file with cropped layers, double check the anchor point, create a Null with the anchor point in the center of the 3 wheels, link rotation property from all wheels to this Null, add offset and / or negative in the expression and animate away the rotation of the Null.