Adrian wrote:
"Mike G" gurgled happily, sounding much like they
were saying:

Because it was low profile, the rim of the wheel was running on the
fold of the tyre.

With a normal size flat tyre the fold is clear of the rim. The fold is
less severe, and not having the weight of the car on it,
is more likely to survive for a short period without damage.

Nothing to do with the profile of the tyre - if the tyre's flat, that's
how the weight on that corner is always going to be borne.

You're wrong. The hight of the tyre from the rim makes a significant
difference. Regardless of profile, when the tyre is flat, the rim drops
straight down, and the sidewalls flex away. In the case of a 60 plus
profile, the rim will in effect run on the part of the tyre nearest the
rim, and the tread of the tyre, with much of the sidewall outside the
actual contact points Because there is less depth of sidewall on a low
profile tyre, the rim can actually run on the folded sidewall itself

I think you're confusing any difference between tread width and rim width
with the height of the sidewall.

The ONLY difference between a flat 60 and a flat 40 profile tyre, of the
same tread width on the same width rim, is going to be the amount of
sidewall hanging out the side. Unless you're thinking the bead somehow
miraculously comes unseated?
I think Mike is thinking that with more sidewall the bend radius is less
severe, so less stressful, which I'd say is correct. However, I reckon
running on the sidewall regardless of the bend severity will quickly
knacker the tyre.