Interesting didn't know tyre pressure on the biscuit wheel was supposed to be so high.
I think that is a "standard" pressure for all space savers, irrespective of what they are on - 4.2bar or 62psi. The big yellow stickers on the actual wheel really identify them, and a couple of times in Germany, I've seen the German plod stopped at the roadside examining any car with a trolley wheel, and actually checking pressures!

BTW, I saw a guy last week pass my on the M50 in a Merc CLS with 3 big alloys and one biscuit on the back doing 90 -100, on the phone and in heavy rain, good cars eh? 
Nowt surprises me. I reckon Merc drivers are the new "BMW" drivers, if you get my drift. Usually, whenever I'm out on my bike, if anyone is trying to kill me, it is always a feckin Merc!
