Does anyone know of an "upgraded" M103 belt tensioner that is a bolt-on using a steel torsion spring rather than the Mickey Mouse "rubber donut".

Elastomers like rubber exhibit a phenomenon called "creep" if under load for a long period causing them to "relax," and if unloaded will not return to their original shape. For this reason only a moron would use rubber as a tensioning device.

Most metals like iron (and its steel alloys) and aluminum alloys have insignificant creep characteristics if loaded below their yield limits. That's why the Brooklyn Bridge is still standing. If it was made of rubber its would have collapsed at least a hundred or more years ago.

Duke