I've always had to make sure that both sides of the chromed spring have a tiny drop of lubricant (use a needle applicator) where they meet the caliper arms, so the spring ends both glide on the caliper posts. If one side of the calipers doesn't slide well as you squeeze the brake lever, you'll have trouble with inaccurate centering until you lube the spring posts. Then, do the above centering with the center mount bolt. I hope this helps