If inflate an unmounted tire to 40 lbs , mount the tire on a car and then lower the jack will it remain at 40 lbs ?
Unless it leaks, there;s no way for air to get in or out.
Seems it would go up slightly as the weight of the car compresses the bottom of the tire. Just a guess, but it’s an easy concept to test.
Pressure is more normally stated in in psi … pounds per square inch…
The question as I understand it, was does the pressure stay constant ?
No. But it only changes a tiny amount, it would be hard to measure it.
The flat spot is only a small length compared to the circumference, and the change in volume is then only tiny. The higher pressure stretches the circumference out some tiny tiny bit, which adds back some of the volume lost to the flat patch at the bottom, and so the change in pressure is reduced… it can never be zero or negative, but its tiny.
Yes, the change is very small - probably too small to measure.
A small amount of Googling led to this discussion, which includes this useful post:
Unmounted can have two meanings. First is the tire is not mounted on the rim. second the tire/wheel assembly is not mounted on the car. I have to admit when I first read the OP, my thought was How the fuck do you get 40 PSI in a tire that is not mounted (on a wheel)?
:dubious:
I can tell you from experience, there is no easily measured difference between airing the tires up off the ground and on the ground (except is is usually easier off the ground)
Similar thread: Does tire patch area + tire air pressure = car weight?
Not one post in that thread pointing out that ‘+’ in the title should be ‘*’ or ‘x’ ? Dopers have clearly refined their nitpickiness in the intervening 11 years.
It’s closer to 12 years.
Nitpickiness restored.
For practical purposes - yes.
If you had thick, tough tires that could barely deform, it might be slightly higher.
You lose credibility by equating weight to pressure so does the answer matter? :rolleyes: