Slight rubbing sound after disc brake conversion

Hello.

I just did the scarebird disc brake conversion. It went on without much trouble. Had to do some extra grinding, but no real complaints about assembly. The brake pedal feels great, and it stops much better.

However, I noticed a slight rubbing sound when I hit the brakes. It's not a grinding sound, like what you would get with old pads and it's not a vibration like warped rotors. After about 30-40 stops, I let the car cool down and then took it for a drive. Didn't hear the rubbing at all, until after about 2 miles of driving it came back.

I pulled the wheels after the drive and took a look, and nothing seems out of the ordinary. The calipers are definitely not rubbing on the wheel, as I thought they might have. No abnormal wear on the rotors.

Anybody have an idea what this could be?