Abstract: An improved lubricant pressure compensator system for an earth boring drill bit for equalizing the lubricant pressure with the ambient or borehole pressure. The pressure compensator is located in a lubricant reservoir that has a passage leading out of the bit adjacent the discharge nozzle. A flexible diaphram is located in the reservoir with its lip seated against the base of the reservoir. The lip protrudes outwardly and a protector member bears downwardly against the lip. A cap bears against the protector member compressing the lip. A retainer ring holds the cap with the lip under compression. A protective centering disc is attached to the center of the diaphram.