The other spring option instead of hammering (which I have never had that much luck with) is to pull the weak side spring out (the one that rubs) and bend it further away from the caliper. Replace. This should balance out the spring action. It's always worked for me.

Since I end up doing it so often, I took an old flathead screwdriver and cut a notch in the blade with a dremel cutting wheel. Gives you a secure hold on the spring while you slip in/out from the tab on the caliper.