Having never had power steering on my last cars, I would be grateful if someone could answer this;
I know the steering will get heavier when the engine is not running, coz the power steering pump is not turning, but have you tried to turn the steering wheel in a ZR/ZS/ZT when the engine is switched off ?
It's damn near impossible, so much so that I thought I might do damage!
I've also tried coasting (I know not recommended :-) ) with the engine switched off for a small stretch and yeah it's heavier but obtainable cos the wheels are turning, but when you've come to a standstill ! no chance or am I just being a wimp ? Just thought if the belt (I assume the P.S. is belt driven) snaps gonna be pretty hard getting home....
look forward to you comments
Gavin :D

Gavin - turning the steering wheel on any car fitted with PAS without the engine running is difficult and it feels as though you'd damage something too!

The Zeds with their big wheel/tyre setup will appear heavier.

If the PAS system fails at speed, the steering will become suddenly heavy but the car should remain steerable [as you have found]

Most PAS Systems use a belt driven hydraulic pump to assist the steering - the exception being the MGF/TF which has an electrical PAS [known as EPAS] system fitted - which seems to work well :)