Does anyone know why the criteria for spring buffers for traction elevators has a different acceptable range than spring buffers for hydraulic elevators?
Traction require 3x the gross load to compress solid, and a minimum of 2x; where hydraulic buffers max load rating is 2x the gross load to compress and minimum of 1x.
Rack and pinion devices also utilize the traction criteria for spring buffers.

A17.1-2016-8.2.3.2, gives the formula for spring buffers. I would guess the difference between the safety plank construction, and the construction of the bolster channel may have somehing to do with the different critera.