Cut the disk as is shown. Cut along the steel wire. This takes some practice, but is easy to do with a helper who keeps the ring in the right position.
Again try to cut smoothly along the wire. This gives maximum width for the disk strip. And it safes work for later cleaning of the ring that contains the steel wire. This asks for good teaming up with your helper. Take safety precautions! Cut the rubber as shown. Do not endanger your helper by cutting in his or her direction.