Vic- I'd do the usual first. Go to high friction pads (Kool Stop Reds), low friction cables (fresh lined casings with smooth/redrawn inners), straddle cable length set for max leverage before I'd replace the cantis. But if you see flex in the cantis (like some cheap stamped steel ones can have) then replace away. Cable routing can effect power. Woman's frames with a convoluted path and/or a pulley attached to the seat binder are known to rob power. Andy.