Proper Tire Pressure
I never found the "correct" answer.
I inflated my tires for the first time myself today. I got confused. Should I follow the max PSI stated on the tire sidewall? Or do I follow what was stated in the driver doorsill? Tire sidewall said 51 PSI. Doorsill said 28 PSI front and 30 PSI rear at driving speeds less than 100 mph.
What is right?
After looking all over the Internet, and asking tire people today, the consensus is: follow the car manufacturer's recommended tire pressure, NOT what is printed on the tire sidewall (or any formula based on the tire sidewall, e.g. 51 PSI +/- 10%). This assumes that you are running OE tires. If you're running non-OE.... All I can say is good luck finding the "correct" pressure!
I wanted to post what I finally found. Because previous threads were inconclusive. In retrospect they were funny to read however because people were going crazy on the boards on this topic. Perhaps I shouldn't have laughed so much, as it can be a very serious topic.
All the best to everyone.
Last edited by spclagent7; Jan 21, 2008 at 10:13 PM.
http://www.tirerack.com/tires/tirete...jsp?techid=147
Last edited by pinebaron; Jan 22, 2008 at 08:53 AM.
https://mbworld.org/forums/newreply....te=1&p=2610301
Not unsafe because still within spec, but does give my new Michelin Pilot Sports better life. Currently after 5,000 miles on the new Mich's I can't see any abnormal wear patterns.
SO for me 32 psi. Some might want softer,, others harder,, but your driving style, tire wear and speeds will determine your "custom" pressure.
Inflate the tires within a couple of pounds of the gas door reccomended tire pressure specs.
Things like temperature, altitude, vehicle load & speed effect what pressure should be actually used.
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remember, those are cold pressures used for baseline... if MB says to use 29/36 (I think that is what is in my doorsill)... what they are really looking for is about 33 and 40 at running temperature on the highway.
in my opinion.. the car feels and handles the best with the front tires running @ 33 front and 39 rear (heated up temp).... so however you get there is your decision
never fill a tire to the pressure on the sidewall...




I started running 32 psi on all four corners and noticed three differences; more even wear on the rear tires, less wandering on the road with higher front tire pressure, and a 2 mpg increase in gas mileage. I now have 27,500 miles on my second set of tires and I expect to get at lease 45,000 miles from the Conti Extreme Contact directional tires. I rotate the tires every 5000 miles.
What is right?
Why Nitrogen?
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Nitrogen inflated tires do not age as quickly as air inflated tires.
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Nitrogen inflated tires minimize blowouts.
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Nitrogen inflated tires improve vehicle handling through proper inflation.
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Nitrogen is an inert, non-combustible and non-flammable gas.
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Nitrogen is a stable gas providing more constant pressure, working better with tire pressure monitoring systems.
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Using nitrogen instead of compressed air has distinct advantages, which lead to immediate benefits for the vehicle owner.
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Compatible with normal air inflation if emergency filling is needed.
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It has more mass, so it migrates through the tire three to four times slower. The result: Tires hold their Pressure longer.
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. It runs about 20% cooler. Less heat results in less tire degradation.
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It drastically reduces oxidation on the rim and inner-liner (nitrogen systems almost totally eliminate oxygen—the cause of oxidation).
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It is environmentally safe.
Who Uses Nitrogen?
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NASCAR - NASCAR teams use nitrogen because it allows them to more accurately predict tire pressure fluctuation.
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Commercial Airlines – The Federal Aviation Administration requires nitrogen in aircraft tires because it reduces the potential for water vapor freezing at high altitudes.
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Beck Imports of the Carolinas.
I've heard that you should not mix nitrogen with air. I don't know which statement is right; I'm not a chemist. Perhaps someone with a bit more knowledge then my high school chemistry classes could shed some light on this. They were offering this at my dealership also but not too many people were going for it.
Courtsey: http://www.getnitrogen.org/why/index.php
Oxygen with air.
It comes that way. I don't worry about humidity in the tires. The outsides see more water than the inside and I check pressure. I would never put N2 in my tires unless I was trying for world speed record.I think N2 in tires is just smoke and Mirrors for more $$.

But then everyone has an opionon. O2 + N2 => O2 & N2 with does not react
Last edited by vettdvr; Jan 28, 2008 at 09:24 AM.
Personally, a good shop air pump does a fairly good job of getting our the water. I don't use the air pumps that sit at one end of the gas station.






