Up Vector Trouble Shooting

[meeting-influence]

Hello,
I am trying to use an up vector.
I do not understand what I am doing wrong.
I am trying to animate a train going around a track. I broke it down into basic elements and am still having the problem of the car not lining up with the wheels correctly, represented by the smaller blocks. I tried using offset, but it still moves.I had the same problem on the model. It looks like I am doing it right but it doesn't line up and stick, like it should. Untitled 1.c4d

[Dr. Sassi]

Hi meeting-influence,

Thank you for the file.

Here is your file back:
CV4_2024_drs_24_ANor_01.c4d

I colored the cubes, in case for follow up questions.

One obstacle was undoubtedly in the "Scale" settings of the objects, being different than 1.0; I would avoid this in animation, as it distorts things down in the hierarchy.

Wheels can make sense in two ways: the axis moves or is fixed.

I have both in the scene and placed a camera on it so it can be easily observed. The camera has no other use here.

I have set the Up Vector to Expression 1, just in case, so it is always calculated after the Align to Spline.

All the best