Phone holder + quieter wheels for the cars from Universität Münster

extension for the cars from Universität Münster
Rest find under:
https://physikkommunizieren.de/3d-druck/experimentierwagen/

Rubber tires for the wheels:
https://www.lego.com/de-de/pick-and-build/pick-a-brick?icmp=PAB_All_Pieces&system=TECHNIC&category=9&query=6552465&selectedElement=6028041