"Lorem Ipsum" > wrote in message
...
> "Joey Tribiani" > wrote in message
> news:fdfee.1412$sy6.1002@lakeread04...
>
> > you are semi-correct...which is the whole point...can you follow me?
> > stepping on the balloon puts MORE force on the outside(pressure)....high
> > altitude puts less.... can't see how that would be it failing for "the
> > same
> > reasons"....the "opposite" I could see,
>
> Yep. The altitude and balloon thing shouldn't even have been in the thread
> because it has nothing to do in reality with the tire issue.
>
>

Well, it sort of is similar. As the balloon rises the pressure outside the
balloon drops. The skin of the balloon can't contain the higher pressure
inside the balloon at a fixed volume (because the skin of the balloon is
neither strong enough nor rigid enough) so it stretches...and
stretches...and stretches. This stretching lowers the pressure differential
between the inside of the balloon and the ouside of the balloon by allowing
the the internal volume to increase.

This continues until the skin of the balloon ruptures.

This is also what happens when you step on a balloon only you reduce the
volume for a fixed amount of a gas (the air) by distorting the shape of the
balloon until the pressure is so great and the skin has stretched so far
that some part of the skin of the balloon ruptures.

When you add weight to a car you distort the shape of the tire. This
distortion reduced the volume inside the tire. The tire stretches some to
help keep the pressure differential reduced but it can't stretch enough to
totally compensate so the pressure inside the tire increases.

When you have a fixed amount of gas (in this case air) in a container (the
tire) and reduce the volume of the container the pressure goes up. This is
why the tire pressure goes up as the weight it is supporting increases.

You already admitted the shape of the tire distorts. Now all you have to
wrap your brain around is the fact that when you distort the shape of the
tire you also reduce the volume inside the tire and the pressure increases.

I'm not going to go into the calculus supporting this. You're just going to
have to research that yourself.