I have a large Padrino with Juicy Ultimates 180 f+r and the rears have been chewing the inside of the chain stay up. There is just a smal amount of clearance between the rotor and frame. When the frame flexes you can hear the rotor digging into the chainstay. Has anyone else experienced this? I'd like to keep the 180 rotor but have resigned myself to going down one size to get some additional clearance.