Does a fully inflated tire (with the rim of course) weigh the same after you let the 40 PSI of air out?

Need fewer troops to support.
Drive a hybrid.
Best tank 71.65 MPG.

Before this car I spent two years learning hypermiling on my 2004 HCH1.

Is this a trick question?

My take is that a wheel under pressure should weight more since we squeeze more air into the same volume as the not inflated tire the weight should go up the more pressure we have

Air at 20C at normal atmospheric pressure is 1.204 milligrams per cubic cm. Not very much.....40psi is about 2.66 atmospheric pressures, so I would guess that at 20C 40psi air weighs about 2.66 x 1.204 = 3.211 milligrams per cm3.
Not very much. So a 14" tire would probably hold about/approx/educated guess, maybe 5 liters??? or 5,000 cm3. Weight of the air maybe would be about 16 grams. Not very much....??? Am I close??? Even at 10 liters of air, 32 grams???? Not very much..

I would have to agree! Good math. The weight of the air in the tires is such a minute level it will not change the overall weight of the tire and wheel comb.

Ok... here's another math problem. I put in 40psi in a tire under no load. Meaning off the car. I then place the tire on the car and jack the car down. I measure the tire pressure again... guess what? It's the same. I have always thought this to be the case but for the life of me, I can't figure out the math to prove this. Anybody?

40 psi means 40 units of pressure per square inch(not that you didn't know that), therefore the air inside the tire is exerting 40 psi against the walls of the tire. When the car is then put under load or sat to the ground the amount of pressure in the tire does not change. However, the shape of the tire that holds the air changes shape still exerting 40 psi. When the tire is under load however, it must have more air in the tire to keep the same `shape when not under load.

For all the Blondes:

Remember to change the air in all your tires at the beginning of winter & summer. this will give you a better ride and it gets rid of the stale air..

04' # 5, W/leather & JBL omitted.
"Prius, Just ask the person that drives one"
04' Tundra, 18mpg city & 22mpg hwy.
04' Prius, 60mpg city & 53mpg hwy.

Kenstyle NHW20 AERO Kit

Probably not too far from the truth. Only because the different gasses that make up air will bleed out of the tire (rubber) at different rates. Argon, Nitrogen, Oxygen. You may end up with more N in your tires by % volume after a certain period of time but I may be wrong or smoking something other than tobacco..

You are supposed to check your tires every month because of temperture changes.

Higher temperature = more pressure
Colder temperature = less pressure

90% of drivers drive with under-inflated tires, more so in Winter.
A tire of today "looks" normal with 50% inflation pressure.
You can't tell pressure by looking at them.
A tire is still drivable with 20% of normal pressure. ( but not safe )

Tires loose 1 psi per month on average, just due to useage.*
Tires loose 1 psi per 10'F temperature drop, on average.*

75% of drivers wash their car once per month.*
14% of drivers check their tire pressures once per month.*
60% of drivers rotate their tires.*

[quote]*
"Vehicle manufacturers list recommended tire pressures for original vehicle tires in the owner's manual or on a placard on the end of the driver's side door or in the glove box.
For continuous high speed driving, tire pressures should be increased by 3 to 5psi above the normal cold inflation recommended.

However, for passenger tires, never exceed the maximum inflation pressure molded on the sidewall. The inflation pressure for light truck tires may exceed that molded on the tire by 10psi. Any recommended front to rear pressure differential should be maintained."


*per Firestone / Bridgestone

FYI
Normal air is 78% Nitrogen, 21% Oxygen, 0.935% Argon, 0.035% Carbon Dioxide. Those 4 alone = 99.98% of air. Not much room for anything else.
Everything else is a few parts per million or parts per billion.
The Myth that certain molecules leak out of the tire at different rates is preposterous. Contrary to some claims, nitrogen does not diffuse through tire rubber more slowly than air. The nitrogen molecules are smaller. All else being equal, smaller molecules diffuse through porous substances more quickly. In real life, oxygen and nitrogen molecules are so similar in size compared to the rubber that there is no net difference in diffusion rates.

Question #2
Which weighs more, a tire filled with Helium, or an empty tire?

Answer: The tire filled with Helium weighs more, as a tire filled with something, must weigh more than a tire filled with nothing.