I brought a spare space saver tyre to place on my D rim. it was off a primera.
The original spare (from 1982) pumped up and took air and didn't leak so decided to keep using it.
once the spare was under load on my d it began to leak after a few hours. I then drove 1 km to my garage to
get the new spare on the rim and on the way it went flat i got 100 meters from the tyre place.
I am sure every one knows this but the original spare may pump up and seem good but once its on the car its a time bomb!
If you have the original spare tyre change it :-) and throw it its great peace of mind