A flywheel for an internal combustion engine, comprising a first element 10, 20 in the form of a sheet steel pressing having hardened peripheral gear teeth 13, 30 for engagement by a starter motor pinion, and a second element 15, 25 of cast iron secured to the first element and affording a friction surface 16, 26. The elements lie in face-to-face engagement over a large surface area for thermal conductivity between them and rigidity of the assembly.