18 inches intermediate rear tyre Low-poly 3D model is available on CGTrader for $49. Original author: mikebibby. Specs: 9588 polys, 9584 verts.
OBJ (OBJ, filesize: 11.6 MB), 3DS (3D Studio, filesize: 5.61 MB), C4D (Cinema 4D, filesize: 5.63 MB), FBX (Autodesk FBX, filesize: 6.1 MB), MAX (Autodesk 3ds Max, filesize: 6.15 MB), MA (Autodesk Maya, filesize: 6.18 MB)