Gravity?
Are you talking about the force encountered during the normal slowing of the elevator to a stop at each floor, or are you talking about what might happen if the emergency brake is applied?
Does the brake have a rated load? More to the point, does it have any means of modulation the way the brake pedal does in your car (you or something presses harder, and the brake applies more force), or is it simply "on" or "off"? What are the implications of that? I know what the answer is, but I'm trying to get you to think about how the device works.
What's the factor of safety between the load capacity of the elevator (including the carriage itself), and the capacity of this brake?
What's the manufacturer say?