It is generally accepted that the maximum available traction is dependent upon three major factors:
i) angle of wrap of the ropes around the traction sheave;
ii) shape of groove profile; and
iii) coefficient of friction between rope and sheave material.



where

	=	ratio between the greater and the smaller static force in the portions of rope situated on either side of the traction sheave in the following cases: - car stationary at the lowest landing level with a load equivalent to 125% of the rated load. - car stationary and unloaded at the highest landing level.
e	=	base of natural logarithms.
f	=	friction factor of the ropes in the grooves.
	=	angle of wrap of the ropes on the traction sheave (radians).