Hack Mount And Blades How Can I Cut Off My Brake Mounts?

How can I cut off my brake mounts? - hack mount and blades

I recently upgraded to a center with 25 and the cassette 9t gear. My brake is mounted on the chain remains in the frame, so I took the brakes. But now the brakes increases are higher than the string and then to push it. I do not think the brake operation at short notice, so no need for a disk brake. What would be the best way to brake the rise cut? A pipe cutter, hack saw, or something else?