Hello everyone,
I have an USD asset of a car that i want animate. I imported it in SOP, unpacked it through USD unpack, made the animation ( a very simple wheels spin) and saved the usd file.
When I import the animation in LOP and sublayer it to the original USD, the scale of the animated wheel is off (it's smaller).
I guess the problem is with the USD unpack, because if I animate the packed USD everything works just fine.
Do you know what I can try to solve this problem?
Thanks

It's possible that the animation is applied to the incorrect prims in SOPs, so when you sublayer back, the results are incorrect. If you have just animated rotation though, I'm not sure why scale would be affected. Can you post the scene, or at least a subset of it? Maybe swap the wheel with a cylinder and delete the rest of the geo, while keeping the hierarchy intact?

I changed the model because it was too big to be attached here, tried it again but same behavior (but this time the scale is way bigger). I also tried to just sublayer the wheels without animation, same story.
I share the scene and the USDs (the main asset is free to use and share).
Maybe something related to the USDZ file format?

That scene is a mess. None of the wheels have their own parent xform, and both sets of front and rear wheels share the same parent, with all sub-objects under that one parent. To make things worse, every single mesh underneath that shared parent is a combined mesh for left and right wheels. The front left and right rubber tyres are a single mesh, for example.

Furthermore, never mind the front wheels being saved as rotated on the Y axis, to simulate a turn, all the wheels are inexplicably rotated on the Z axis, so they're all off-balance and if you try to spin them, they'll wobble.

To fix this, you need to isolate the wheels in SOPs, align them correctly, give each one their own hierarchy, and then re-export back to USD, while pruning out the original wheels.

Personally, I'd just use a different model.

First of all thanks for had a look to the scene.
Yes, it's a mess. I've found the almost every model from sketchfab have this "auto-generated" USDZ files, so it's not evene at artist fault.
I'll follow your advise, and use the normal FBX workflow (I was tryng to avoid the re-assign material phase, but it is what it is ).
Thanks again for your time!