Tire Pressure. when will it stop dropping and raising?

[Solodays]

it is said that tire pressure drops 1 psi in every 10 degree drop in the winter and raises 1 psi in every 10 degree raise in summer.


my questions is.. lets say, at the tires default setting at 30psi, at about what temperature does tire pressure starts dropping and starts raising? theres gotta be a temperature at which it start dropping, if not, it wouldn't make sense to say that at 50F today and 40F tommorrow you'd lost 1psi. the temperautres gotta be cold enough and hot enough in order to do so, theres gotta be a fix cold temperature and hot temperature inorder to drop and raise, if not then your tire pressure would probably fluctuate daily, am i correct?

 

[Jahee]

It will fluctuate daily yea.. just like if you've been working the tires harder, they'll get warm as will the air inside and pressure will increase..

To answer the question there's not a fixed temp it will change with and change in pressure with any increase in temp

 

[Heisenberg]

PV=nRT

 

[Solodays]

any increase in temp? 60f to 50f sure aren't that dramatic. it's hard to believe you'd lost 1 psi from there.

 

[Jahee]

Don't know the exact ratios, but a decrease of 0.1F would cause some decrease in pressure.

 

[Evadman]

Originally posted by: Solodays
my questions is.. lets say, at the tires default setting at 30psi, at about what temperature does tire pressure starts dropping and starts raising? theres gotta be a temperature at which it start dropping, if not, it wouldn't make sense to say that at 50F today and 40F tommorrow you'd lost 1psi. the temperautres gotta be cold enough and hot enough in order to do so, theres gotta be a fix cold temperature and hot temperature inorder to drop and raise

double the temp, double the pressure. halve the temp, halve the pressure. Basic thermodynamics. The 1 PSI per 10 degree drop is for people who don't know basic things like 'only check tire pressure when cold' along with knowing that there are numbers between 0 and 1.

 

[HESDog]

Originally posted by: Heisenberg
PV=nRT

PV=ZnRT

 

[Suspicious-Teach8788]

/

Originally posted by: Evadman

Originally posted by: Solodays
my questions is.. lets say, at the tires default setting at 30psi, at about what temperature does tire pressure starts dropping and starts raising? theres gotta be a temperature at which it start dropping, if not, it wouldn't make sense to say that at 50F today and 40F tommorrow you'd lost 1psi. the temperautres gotta be cold enough and hot enough in order to do so, theres gotta be a fix cold temperature and hot temperature inorder to drop and raise

double the temp, double the pressure. halve the temp, halve the pressure. Basic thermodynamics. The 1 PSI per 10 degree drop is for people who don't know basic things like 'only check tire pressure when cold' along with knowing that there are numbers between 0 and 1.

Uhhh, you are speaking with respect to absolute temperature and FAHRENHEIT is not a scale you use when you do that. Either you use Rankines or Kelvin, but honestly, who does a freaking PV=nRT? Moreover, PV = nRT is complete absurdity because it is ideality. If you even want to talk thermodynamics, there's a lot more factors. You might need to consider vapor pressure, free energy and entropy when dealing with nonideal stuff. The Clausius-Clapeyron equation is more suitable. 1 PSI per 10 degree drop is perfectly fine. It's just like people in poker use # of outs * 4 on the flop and # of outs * 2 on the turn. It's not exact probability, but no one wants to do 5/46 * 4/45 math ok?

 

[Midlander]

Over the temperatures you are experiencing, PV=nRT will do just fine. You won't be able to measure any closer with a typical tire gauge than the equation will get you.

Just remember to use the right temperature scale.

 

[MikeyIs4Dcats]

didn't pay much attention in school did you?

 

[Minerva]

It would be neat to fill tires with mercury.

 

[Tiamat]

At pressures less than 20 atm, and normal temperature, the Ideal gas law is a great equation to use. Only gases like CO2 start to deviate at high pressure (20 atm).

 

[Evadman]

Originally posted by: DLeRium
/

Originally posted by: Evadman

Originally posted by: Solodays
my questions is.. lets say, at the tires default setting at 30psi, at about what temperature does tire pressure starts dropping and starts raising? theres gotta be a temperature at which it start dropping, if not, it wouldn't make sense to say that at 50F today and 40F tommorrow you'd lost 1psi. the temperautres gotta be cold enough and hot enough in order to do so, theres gotta be a fix cold temperature and hot temperature inorder to drop and raise

double the temp, double the pressure. halve the temp, halve the pressure. Basic thermodynamics. The 1 PSI per 10 degree drop is for people who don't know basic things like 'only check tire pressure when cold' along with knowing that there are numbers between 0 and 1.

Uhhh, you are speaking with respect to absolute temperature and FAHRENHEIT is not a scale you use when you do that. Either you use Rankines or Kelvin, but honestly, who does a freaking PV=nRT? Moreover, PV = nRT is complete absurdity because it is ideality. If you even want to talk thermodynamics, there's a lot more factors. You might need to consider vapor pressure, free energy and entropy when dealing with nonideal stuff. The Clausius-Clapeyron equation is more suitable. 1 PSI per 10 degree drop is perfectly fine. It's just like people in poker use # of outs * 4 on the flop and # of outs * 2 on the turn. It's not exact probability, but no one wants to do 5/46 * 4/45 math ok?

Exactly. Thanks for using lots of really big words that Solodays doesn't understand and proving my point.

 

[sdifox]

Originally posted by: Minerva
It would be neat to fill tires with mercury.

err, kindda heavy no? and it probably doesn't absorb shocks as well as air. never mind it's toxic as hell.

 

[ScottFern]

nitrogen ftw?

 

[Kalvin00]

Originally posted by: Minerva
It would be neat to fill tires with mercury.

The car's weight would be double just because of the tires..

 

[Zenmervolt]

Originally posted by: Solodays
any increase in temp? 60f to 50f sure aren't that dramatic. it's hard to believe you'd lost 1 psi from there.

While it may be hard for you to believe, it's still true. Technically, _any_ change in temperature will cause a fluctuation in tire pressure, it's just that for small changes it's not a significant fluctuation.

Just driving the car causes enough heat in the tires to raise the pressure by 3-5 PSI. This is why you should always set the tire pressure after the car has been sitting for an hour or when it has been driven less than a mile.

ZV

 

[Zenmervolt]

Originally posted by: Minerva
It would be neat to fill tires with mercury.

Except for that pesky toxicity thing.

ZV

 

[GuitarDaddy]

Originally posted by: Kalvin00

Originally posted by: Minerva
It would be neat to fill tires with mercury.

The car's weight would be double just because of the tires..

Not to mention the centrifical force would tear the tires apart in short order

 

[Muadib]

Originally posted by: ScottFern
nitrogen ftw?

:thumbsup:

 

[FoBoT]

maybe you have a small hole, in the tire

 

[LS20]

related question - how would one fix a tire that has a slowwwww leak?

mine seems to drop 10psi every 2 weeks

 

[Minerva]

Originally posted by: Kalvin00

Originally posted by: Minerva
It would be neat to fill tires with mercury.

The car's weight would be double just because of the tires..

Unsprung weight does funny things. On the driven wheels it would help in the snow. Liquids in tires are bad though. Throws the balance WAY off. Hg is quite dense.

This reminds me of this thread. :Q

The best prank is to hook a decent vacuum pump up to a tire. It will assume the shape of a flower.

 

[Chryso]

I think you are making an assumption that there is a baseline temperature at which there is a "correct" pressure. I don't believe this is true. At all temperatures the pressure is relative.

 

[FoBoT]

Originally posted by: Chryso
At all temperatures the pressure is relative.

yeah, to atmospheric pressure, which changes with the weather

it isn't like the tire pressure has to be exactly XX.XXXX psi

as long as it is close to a band, it'll be ok