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Just a reminder to check your tire pressure

Discussion in 'DIY (Do-It-Yourself)' started by Devilsown, Dec 23, 2008.

    Devilsown guest

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    I just thought I'd post a reminder, With the winter now here the weather has gotten cold, be sure to check your tires as Im sure they have lost a few pounds of air. I had to a few pounds of air in my tires.

    Autohaus guest

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    Most definitely. I have to add some air to the xi tonight as I noticed the front drivers side tire was a tad low :(
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    elfhearse

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    Rule of Thumb is 1 PSI for every 10°F drop

    missmelyssa guest

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    Good rule, thanks.
    And in the bay area of sunny california, we were experiencing quite a cold winter.
    Snow in San Franciso? Yup.
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    Jeff Gomon

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    The ol' M5 has been garaged since the first snow flew over a month and a half ago. It was about 55 deg when I upped the pressure to 38psi for winter storage. It was very cold (5 degrees), but dry this past weekend so I backed her out to let her warm up a bit. All tire pressures were near 32psi with one being 30psi. I added a few pounds (35psi) and drove it back in. My garage stays at 50-55deg all winter with my self added supply vent from the house system bleeding a little heat in there. Checking today, with the garage temp at 52, pressures have elevated back to 38-39psi, so temp certainly affects tire pressures more than you think. A bit more pressure will also help to lessen flat spotting that some tires display on initial startup.

    If you track you car, you will really see a difference in pressures, and tire performance, based on cold tire temps and on track tire temps.

    1996 328ti guest

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    Track? That's just crazy talk. :eek:

    mackmorrowjr guest

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    Be sure to check tires cold. Ie, when car has not been driven for at least 3 hours or less than one half mile.
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    Jeff Gomon

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    Good point Mack.....

    Tire pressure maximums that are molded into the tire sidewall are all representative of cold temp readings. Manufacturers have set these pressures knowing well that temps, and overall pressure, will increase while driving. That "at temp" pressure is where the tire is actually designed to operate, and can be 4+ psi higher. If you go for a drive and set the pressure right afterward to the pressures on the sidewall, when the tires cool down, they will always be under inflated.

    Further, the pressure settings that are posted inside the drivers door jamb, or in the owners manual, is what the manufacturer has found to be optimal overall during testing using the OE tires. If you have changed to a different type of tire, say a snow tire, or a tire with different load ratings etc, these numbers will not be the same. At that point, follow the sidewall pressures and look for performance and wear indicators to adjust the pressure properly from there.

    We don't even want to get started with Nitrogen filled tires do we?!?!?!?!?:eek:

    Devilsown guest

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    Well I think you just started the snowball rolling at the top of the hill :D Do wish I had some nitrogen form mine though...
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    Jeff Gomon

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    Nitrogen Information....

    First, sorry for the length of this post.... :rolleyes:

    Devilsown,
    I personally have a small compressed nitrogen bottle that I carry in my track trailer for topping up pressure. I bought the pressure gauges at a welding supply house and just get a new bottle annually. It is much cheaper than oxygen and the 18"-24" high bottle is only a bit bigger than a 2 liter coke bottle. Only about $9-$12 per bottle. I leave it in my trailer for my track traveling buddies to use and I'm impressed how long it lasts. The bottle holds 2400-2600psi so when adjusting a few pounds here and there, it only goes to figure it would last. For me, it is for convenience and price I use this setup.

    Nitrogen is a very common fixture at my other job. Aircraft tires use nitrogen because it does not expand or contract as much as oxygen with the different altitudes and temperatures experienced during flight nor is it as affected by the very hot brakes. It is also it does not support combustion. Take off in Vegas at 117deg and climb to 36k feet where it is -65deg in a matter of a few minutes and imagine the opportunity for pressure change.

    Breathable air contains roughly (by molar content - equivalent to volume, for gases) 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, and trace amounts of other gases; but air also contains a variable amount of water vapor, on average around 1%. Therefore, your tires have almost 80% nitrogen in there anyway.

    I did some more research and here is what I found, in a nutshell, on the website "The Straight Dope"...Fighting ignorance since 1973...and its taking longer than we thought". (copied and pasted of course)

    Are there benefits for using Nitrogen in automobile tires?

    Oh, there are plenty of benefits: (1) Cool fluorescent green valve stem caps (assuming your nitrogen vendor has any marketing savvy), which will look sharp with your spinning wheel covers. (2) Bragging rights. OK, you were behind the curve with cell phones, iPods, thong underwear, etc. Nitrogen in tires is relatively new to the mass market. Now's your chance. (3) Reduced fire danger next time you land your space shuttle or commercial aircraft, and tell me you won't sleep better knowing that.

    Filling your tires with nitrogen mainly does two things: it eliminates moisture, and it replaces skinny oxygen molecules with fat nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That means, theoretically at least, that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. The commonly quoted figure is that tires inflated to 32 psi get 3 percent better mileage than at 24 psi.

    As for moisture, changes in humidity affect tire performance two ways. First, the density of humid air fluctuates more with temperature than that of dry air, so removing humidity can keep your tire pressure more consistent, especially when the temperature climbs over 100 degrees Fahrenheit. That may be a legitimate concern in Formula One racing, but it's not much of an issue if you're just tooling around town.

    Humidity can also be a factor in wheel maintenance - since pure nitrogen doesn't have moisture in it, supposedly your wheels won't rust as quickly, which could lead to improved wheel performance and air sealing. The question is, how big a problem is wheel rust these days? According to a few tire and wheel shops we contacted, not very. Seriously rusted wheels are uncommon in typical steel-wheeled cars, and many high-performance cars have alloy wheels that don't rust at all. One exception is work vehicles such as dump trucks, which are exposed to a much harsher environment.

    Overall, filling up with nitrogen won't hurt and may provide some minimal benefit. Is it worth it? If you go to some place like Costco that does it for free with new tires, sure, why not? Elsewhere, though, I've seen prices quoted as high as $10 per tire, which is way more than I'd pay. Rather than shell out for nitrogen, you'd be better off just checking and adjusting your tire pressure regularly, something the NHTSA says less than 60 percent of U.S. motorists actually do.

    Devilsown guest

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    good stuff, I work on a flightline and if I could only use the "nite" (nitrogen) cart for about 10min... I would be happy But im sure they would frown on a POV in a restricted area :rolleyes: but for now I'll just adjust tire pressures as needed.

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