My bb7 rear disc road brake is making a lot of noise NOT when I brake but when pedaling (no issue with coasting either). I got to the point on a ride where I was keeping pressure on the brakes; so pressing the pads gently against the rotor to stop the noise. I opened up the caliper on one side then the other significantly - as much as I could to still have braking power. It didn't work - maybe slightly better but not much. I checked the rotor when I got home and it seems solidly straight - maybe 1/2mm wobble at one point but with the pads open the rotor was no where near the pads on the stand. It has something to do with being under load and the "ping" sound is not periodic and only happens while pedaling.

It's almost as though the magnet and spring are not holding the pads properly against the caliper - except I'd expect pinging noise while coasting too. I'm going to try new pads. I have never replaced the spring as my LBS sells the pads without the spring. When should I replace the spring? It seems fine.

Any ideas?