Since I bought my new Ford Focus MY2012 I noticed that the emergency/parking brake varies its limit randomly.
Sometimes the limit requires 3 steps, sometimes 5 or 6 steps.

I can't figure out if it depends on ground inclination or cold fluids (after a long parking time).

I ask other friends with the same car model and they reported the same behaviour.

The car is equipped with 4 disc brakes (front and rear) but I don't know if the emergency brake use a dedicated separate drum brake system or it simply mechanically operates the original rear discs.

Anyway why the emergency brake travel (and stiffness) is so variable? (Since it happens on many similar models I suppose it's normal, but why?)

Thanks a lot, this question don't let me sleep :P
Matteo