PSA: Check PSI

[amdhunter]

This morning, I turned on my car and saw a nice yellow light on my dash. Turns out one of my tires was low and tripped the sensor. None of the tires were flat looking or felt soft, but I went to the gas station to check them anyway.

Turns out every single tire were way out of spec. Normal pressure is 38PSI, and three were at 32, one was at 29. I guess the one at 29 tripped it.

Anyway, I filled the tires to 38PSI exactly, and headed on my way. I got to say the car feels like brand new, rolling with ease now. Even shifting seems smoother lol.

I guess the colder NY air had an effect on them. Last time I checked the tires was probably back in February or so.

Is a 6 PSI loss something to really worry about at all? It's been months since I last filled them. And they seemed to wear down evenly across all tires.

 

[sdifox]

dude, I check tire pressure every 2 weeks.

 

[boomerang]

I don't think what you've experienced is out of the norm.

A tire inflated with air will drop about 1 PSI for every 10 degrees drop in temperature. The converse is true as the temperature rises.

My current car came from the factory with Nitrogen in the tires. I always thought this was a gimmick for a passenger car. I've had the car for 8 months and the tire pressure has not dropped. I also have seen very little change in pressure with temperature changes. I'm sold on Nitrogen.

We just picked up a new car for my wife yesterday and I am thinking of going Nitrogen in those too.

 

[amdhunter]

Originally posted by: sdifox
dude, I check tire pressure every 2 weeks.

I treat tires like one of those things I never need to check. Thank goodness for sensors for dumb people like me.

 

[Vette73]

What car and tires do you have??? 38PSI is way to high for most car tires

 

[Demon-Xanth]

Nice thing about tall sidewalls, you can check your tire pressure from 10 feet away

 

[Toastedlightly]

Originally posted by: boomerang
I don't think what you've experienced is out of the norm.

A tire inflated with air will drop about 1 PSI for every 10 degrees drop in temperature. The converse is true as the temperature rises.

My current car came from the factory with Nitrogen in the tires. I always thought this was a gimmick for a passenger car. I've had the car for 8 months and the tire pressure has not dropped. I also have seen very little change in pressure with temperature changes. I'm sold on Nitrogen.

We just picked up a new car for my wife yesterday and I am thinking of going Nitrogen in those too.

Too easy!

 

[Billb2]

And how much extra gas did you burn and how many unsafe miles did you crank off, while you car was not in optimum handling form, because "I treat tires like one of those things I never need to check"?

And what kind of car/tires needs 38psi? That's pretty high.

 

[amdhunter]

Originally posted by: Marlin1975
What car and tires do you have??? 38PSI is way to high for most car tires

07 Jetta GLi with some low-profile Dunlops.

 

[Vette73]

Originally posted by: amdhunter

Originally posted by: Marlin1975
What car and tires do you have??? 38PSI is way to high for most car tires

07 Jetta GLi with some low-profile Dunlops.

Yep, that is to much pressure. Most fall into the 30-35psi range.

I have my CTS and Corvette at 32 front and 30 rear.
38psi will cause them to wear to much in the middle, esp the rear.

 

[Baked]

Tire pressure should be printed in your glove compartment if you're one of those people who don't read the manual. My car comes stock w/ low profile tires, 32F/29R.

 

[fbrdphreak]

Originally posted by: Baked
Tire pressure should be printed in your glove compartment if you're one of those people who don't read the manual. My car comes stock w/ low profile tires, 32F/29R.

I didn't know that - I thought it was usually on the driver's side door frame?

BTW - Nitrogen FTW. $40 for lifetime fill/refill of nitrogen in the tires, plus roadside assistance included. Nitrogen looses far, far less over time and as anecdotal as it may be, my buddy running super soft tires on his Evo got a substantial bump in life out of the tires.

http://www.nitrofill.com is one

 

[spidey07]

Tire pressure is listed on door jamb.

Of course they were low, it's getting colder. Check your tires at least one a month. Also tires won't "look like they're running low" until they are VERY low, like 10 pounds low.

 

[bruceb]

6 PSI over 8 months is not too bad .. But you should check them every other week or so. And they will go down in reading in Winter and UP in PSI reading during Summer ... for most cars, 33 to 35PSI is good. If you like a softer ride, without too much handling loss, then drop down to about 30PSI

 

[Arkaign]

BARACK OBAMA!

<----- P&N !!!

lulz

 

[amdhunter]

Originally posted by: Marlin1975

Originally posted by: amdhunter

Originally posted by: Marlin1975
What car and tires do you have??? 38PSI is way to high for most car tires

07 Jetta GLi with some low-profile Dunlops.

Yep, that is to much pressure. Most fall into the 30-35psi range.

I have my CTS and Corvette at 32 front and 30 rear.
38psi will cause them to wear to much in the middle, esp the rear.

It's on the door. 38 all around. I thought it was a bit high also at first.
3 of the tires were at 32PSI already, and it felt sluggish at hell. It feels a ton better now with just a 5PSI increase.

 

[amdhunter]

Originally posted by: Billb2
And how much extra gas did you burn and how many unsafe miles did you crank off, while you car was not in optimum handling form, because "I treat tires like one of those things I never need to check"?

And what kind of car/tires needs 38psi? That's pretty high.

Probably a whole lot. The car is rolling a lot easier now.

 

[Maximus96]

my mini cooper requires 38psi for runflats. i put 36

 

[Howard]

Originally posted by: boomerang
I don't think what you've experienced is out of the norm.

A tire inflated with air will drop about 1 PSI for every 10 degrees drop in temperature. The converse is true as the temperature rises.

My current car came from the factory with Nitrogen in the tires. I always thought this was a gimmick for a passenger car. I've had the car for 8 months and the tire pressure has not dropped. I also have seen very little change in pressure with temperature changes. I'm sold on Nitrogen.

We just picked up a new car for my wife yesterday and I am thinking of going Nitrogen in those too.

Sorry, but as nitrogen makes up about 78% of air, the pressure/temperature relationship is not significantly different.

 

[zerocool84]

Originally posted by: spidey07
Tire pressure is listed on door jamb.

 

[bruceb]

They use nitrogen because it has no moisture in it. As such, while the pressure will change with temperature changes, the amount of the change will be much smaller. See link below:

http://auto.howstuffworks.com/question594.htm

Why don't they use normal air in race car tires?

Many race car teams use nitrogen instead of air in their tires because nitrogen has a much more consistent rate of expansion and contraction compared to the usual air. Often, a half pound of pressure will radically affect traction and handling. With track and tire temperatures varying over the duration of a race, the consistency of nitrogen is needed.

Nitrogen pressure is more consistent than normal air pressure, because air typically contains varying amounts of moisture due to changes in the relative humidity on race day. Water causes air to be inconsistent in its rate of expansion and contraction. So, a humid race in the southeast United States or a dry race in the desert western United States could make for unpredictable tire pressures if "dry" nitrogen were not used.

Nitrogen is also used in the high-pressure tires on large and small aircraft.

 

[boomerang]

Originally posted by: Howard

Originally posted by: boomerang
I don't think what you've experienced is out of the norm.

A tire inflated with air will drop about 1 PSI for every 10 degrees drop in temperature. The converse is true as the temperature rises.

My current car came from the factory with Nitrogen in the tires. I always thought this was a gimmick for a passenger car. I've had the car for 8 months and the tire pressure has not dropped. I also have seen very little change in pressure with temperature changes. I'm sold on Nitrogen.

We just picked up a new car for my wife yesterday and I am thinking of going Nitrogen in those too.

Sorry, but as nitrogen makes up about 78% of air, the pressure/temperature relationship is not significantly different.

Sorry, but you are incorrect.

The rule of thumb is for every 10° Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower).

The above is a quote from the following article:

http://www.tirerack.com/tires/...techpage.jsp?techid=73

I crewed on a racing team for approximately 8 years. This fact was readily apparent to me on a regular basis. It's not just the Oxygen content, it's the humidity that goes along with it that affects pressure changes. This is one of the pluses with pure Nitrogen. It has 0% humidity.

Edit: I see bruceb already pointed out the effects of humidity.

 

[spidey07]

boomerang, you must include and admit that in racing the temperature swings are much higher and much more important than passenger vehicles.

 

[boomerang]

Originally posted by: spidey07
boomerang, you must include and admit that in racing the temperature swings are much higher and much more important than passenger vehicles.

Absolutely, no argument there.

But I wasn't referring to racing in my first post. I saw this in my personal cars before Nitrogen came on the scene. Before Nitrogen and Tire Pressure Monitors, I was a once a month tire pressure checker. The point to my correction post was that I wasn't pulling facts out of my ass. I didn't make this stuff up. It's nothing new. It's been known for a long time.

 

[Howard]

Originally posted by: boomerang

Originally posted by: Howard

Originally posted by: boomerang
I don't think what you've experienced is out of the norm.

A tire inflated with air will drop about 1 PSI for every 10 degrees drop in temperature. The converse is true as the temperature rises.

My current car came from the factory with Nitrogen in the tires. I always thought this was a gimmick for a passenger car. I've had the car for 8 months and the tire pressure has not dropped. I also have seen very little change in pressure with temperature changes. I'm sold on Nitrogen.

We just picked up a new car for my wife yesterday and I am thinking of going Nitrogen in those too.

Sorry, but as nitrogen makes up about 78% of air, the pressure/temperature relationship is not significantly different.

Sorry, but you are incorrect.

The rule of thumb is for every 10° Fahrenheit change in air temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower).

The above is a quote from the following article:

http://www.tirerack.com/tires/...techpage.jsp?techid=73

I crewed on a racing team for approximately 8 years. This fact was readily apparent to me on a regular basis. It's not just the Oxygen content, it's the humidity that goes along with it that affects pressure changes. This is one of the pluses with pure Nitrogen. It has 0% humidity.

Edit: I see bruceb already pointed out the effects of humidity.

You misunderstand me. I said that nitrogen was the major component of air.

As air follows the ideal gas law pretty closely, for a closed volume the pressure is proportional to temperature. Nitrogen is no different, especially as it also behaves like an ideal gas and is pretty much the same as air.

I don't see where you proved me wrong at all.

EDIT: I think I'm wrong. I didn't think that the water content affected the p-t relationship so significantly... Still, I'd like to see some hard numbers.