As I recall it was somewhere in the range of around 250psi, and the
magnesium wheels have a blow out plug to keep the thing from exploding.
However, I still wouldn't want to be anywhere near if the thing let go.

We taxied up next to one with hot brakes, which we called on the radio, and
I couldn't wait until the ordinance guys did their check to get out of
there- it seemed like the wheel was pointing right at us.