Hello, looking at the CAD it seems like you may have to resolve the wheel central axis in x, y and z components for each wheel and enter all the three components in the rotation axis direction as the central wheel axes are not parallel to global coordinate system.
To know more, please refer to a section of the Ansys Fluent's User Guide whose link is given below. After opening the link, please have a look at wall boundary conditions.
7.4. Boundary Conditions (ansys.com)
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