feeler gauge is the key
A .017 worked for me this time. Simple, satisfying process. I used a rubber ring for mounting a Garmin unit to hold the brake closed while I tightened the caliper bolts. The brake pressure held the feeler blade in place, leaving both hands available. Thanks so much for the tip.
Stumbled on the following technique, probably old news to many, but maybe helpful for some new to hydraulic disc brakes.
If you loosen the caliper mounting bolts, squeeze the brake lever, and tighten the bolts, your brakes may drag if the pads don't retract equally. In that case, shine a light to see which side is rubbing. Then repeat the procedure, but slip a feeler gauge between the rotor and the pad on the side that rubbed, before squeezing lever and tightening bolts. A 0.015" feeler gauge is a good place to start, and you can use a larger or smaller one if the first try still results in rubbing pads.
I recently bought a disc brake alignment tool, but it didn't eliminate drag. The feeler gauge achieves both alignment and even spacing; bliss![/QUOTE]