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?

new pads should include new spreader springs..

My LBS sells the pads without springs because they don't need to be replaced every time. Nevertheless, I will be replacing the springs to rule out that possibility.

You should use new springs every time new pads are put in. Get a new LBS, new springs come with new pads in the box.

I suspect it isn't the brake making the noise if moving the pads bad didn't change the sound.
Wind the pad adjusters all the way back - or remove the pads and try the bike.
Have you checked for play in the hub axle and bearings? Quick release is tight?
Are you following the correct adjustment procedure? A lot of people try to adjust with the cable which is incorrect.

but don't try the bike down a hill.

This sounds somewhat like BB7 pad toe in/out issues. I just give up when I find a Avid caliper that won't hold the pads flat, nothing seems to fix the problem.

Rotors should have no detectable wobble. That's most likely your problem. Bend it straight or get a new rotor.

Ah, the joys of disc brakes.

I now believe it's the hub. It's an explanation that makes the most sense. The pads are not hitting the rotors at all while coasting - only under load. I check the wheel: spoke tension good and it's true. I try to wiggle the axle and seems fine but I doubt I can wiggle it at the load it's under while pedaling hard (up hills were the worst).

Edit: axle does move; tiny and only in some positions.

Adjusting this hub is probably over my pay grade ...

Disc brakes are the biggest pita ever. High maintenance, noisy. Yet I've drunk the cool-aid and I will stick with them.

I suspect this isn't the problem BUT I totally agree that the pads move around a little too much for my liking. Any suggestions for disc brake calipers?

for anyone interested: Adjusting the hub was really very easy (WI provides good online instruction). It was the hub. Nice, quiet 30 mile ride today. The tech gal at WI (who is amazing) told me to check for axle movement after this ride and if axle movement then bearings must be replaced.