Originally Posted by dbakl

First, make sure the 2 nuts on the front are correctly adjusted to allow the arms to move freely. The second nut holds the arms, the outer nut locks the position. Sometimes hard to adjust.

Put a punch or a screwdriver on the top of the spring of the arm that's too far away. Give it a firm but gentle wack to spin the main mounting bolt slightly. Sometimes you have to go back and forth a few times to perfect. Squeeze the brake lever a few times each time to see where the caliper recenters itself.

This was the traditional oldschool way of centering calipers, before Campagnolo put the cone wrench slots on the center bolt.