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OK...I looked through the existing tire pressure threads about this but I'm still left wondering. After I drove off the lot with my new car, I noticed that the PSI was 35#s all around. The door jam sticker for these GoodYear Eagles states 32#s front and back. I mentioned this to my service advisor last week when I brought it in. So, I check my PSI and now it's 38#s. They're nitrogen filled so they shouldn't vary much with the moderate temps (50° - 75°).

What PSI are you running with?
 

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When I picked my TLX up last month I noticed the PSI was 38 on all 4 tires and I asked my salesman about it. He said they always overinflated a little in the winter because they tended to lose a little due to temperatures. When I checked a couple of weeks later they were down to 35 lbs pretty much all the way around. With my previous TSX my indicators would indicate low pressure anytime the temperature got down below 30 and then would stop indicating when the temperature got above 50. I tried to maintain them at 32 psi. Based on what my salesman told me I will probably try and keep them in the 35 range.0:)
 

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When I picked up my car, all the tires read 31 or 32 psi, cold, in 50 degree F temps in early December. I have 19" acura rims. This dropped to below 30 psi when temperatures dropped routinely below freezing, even though a long highway drive took them to 34-35 psi during the drive.

With temperatures routinely hitting well below zero in the NH ski mountains, and my propensity to spend as much of winter skiing on the snow rather than shoveling it, I filled my tires to 34 psi cold, which rises to 37-38 during long highway drives and that's been fine for me.

There is some flexibility here so long as you never exceed the maximum tire pressure. It's basically a trade-off in handling vs. ride comfort. I found the front tires too spongy in turns at the lower psi, and found 34 psi cold matched my driving desires better, even if it means a slightly harder ride and being more careful around those nasty evil potholes.
 

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Don't trust the read-out that the car indicates on the dash display. I have a couple of nice pressure gauges that always read within a half pound of each other, when I set the tires to 32 lb. the dash display reads around 37 lb. And yes I am talking cold not when the car has been driven (then the dash display goes up to 39 - 40 psi)
 

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Don't trust the read-out that the car indicates on the dash display. I have a couple of nice pressure gauges that always read within a half pound of each other, when I set the tires to 32 lb. the dash display reads around 37 lb. And yes I am talking cold not when the car has been driven (then the dash display goes up to 39 - 40 psi)
There's a good chance the system might take a while to 'catch up' and get the right number.
 

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Maybe you should double check with a second tire pressure gauge as it could be the gauge that is slightly off.
 

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I was going by the door label, but last time I let the car tell me when it had enough. When there was enough pressure The TLX would beep at me. :)
 

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"They're nitrogen filled so they shouldn't vary much with the moderate temps (50° - 75°). "


There are a lot of reasons that people claim that nitrogen is a better option for your tires but the one you brought up is actually not true. Oxygen and nitrogen have very similar rates of thermal expansion. In fact, all gasses have virtually identical rates of thermal expansion. Even if this wasn't true, the air that you breath is less than 20% oxygen with the vast majority of the remainder being nitrogen. Pumping that into your tire at a local gas station is effectively pumping 80% nitrogen into your tire anyway!


A more credible reason for using nitrogen is because it doesn't cause oxidation. This is likely not truly a factor as the tire and wheel are both exposed to oxygen on their exterior surfaces.


The only reason that I've seen that holds water is that Nitrogen molecules are large and less likely to work their way through the rubber. This allows the tire to retain pressure slightly better. I still wouldn't say this is a good reason to pay to have nitrogen used versus normal air as most pressure loss occurs at the stem and from repaired damage.


At the end of the day there is a lot of hype around the tire world regarding nitrogen. I personally wouldn't go out of my way for it, especially if it was going to cost me $.
 

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Besides the Nitrogen having larger molecules, I heard it also does not feed a fire like normal air or oxygen would.

To me the ride feels smoother. Is this true or just in my head? :)
 

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It's true that it won't feed a fire. This is the reason they use nitrogen in airplane tires. That said, my car isn't 70,000 pounds. I haven't seen a single tire light on fire from the inside. The fire tends to start on the outside due to friction caused by under-inflation. The benefits here are pretty marginal.


The smoothness of the ride is not likely to be related to what you fill it with. It's the same point as I'd made before, all gasses will maintain the same volume at equivalent temperature and pressure.


I'm not saying nitrogen isn't better in a number of ways, just that the difference is marginal (i.e. not worth paying for).
 

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It's true that it won't feed a fire. This is the reason they use nitrogen in airplane tires. That said, my car isn't 70,000 pounds. I haven't seen a single tire light on fire from the inside. The fire tends to start on the outside due to friction caused by under-inflation. The benefits here are pretty marginal.

The smoothness of the ride is not likely to be related to what you fill it with. It's the same point as I'd made before, all gasses will maintain the same volume at equivalent temperature and pressure.

I'm not saying nitrogen isn't better in a number of ways, just that the difference is marginal (i.e. not worth paying for).
Yeah. I remember in the Navy we used nitrogen for the tires. I also used it for the waveguides for the radar systems to prevent arcing and sparking.

Have you had any experiences working with Nitrogen? Maybe give us some background on your gasses knowledge. It would be nice to know we are talking to an expert. :)
 

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I don't work with gasses really. Everything I mentioned is stuff I remember from high-school physics and chemistry. None of it requires an advanced degree. I went back and double checked online before I posted, just to be sure. Rates of thermal expansion with regard to pressure are functions of Boyle's law and the Ideal gas law.
 

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I don't work with gasses really. Everything I mentioned is stuff I remember from high-school physics and chemistry. I went back and double checked online before I posted, just to be sure.
Thanks. I was just curious. :)
 

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If you don't want to take my word for it, here's the argument as presented by a few major players in the industry:
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[Edited for clarity]
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Sorry if I came across like I didn't trust you. I was just curious about your background.

I try to be open to other opinions. It's amazing how much you can learn.

:)
 

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One of the sales pitches made to me were that the molecular size of Nitrogen versus common air makes for slower pressure loss over time. However since Nitrogen is very prevalent in every day air I struggle to buy in.

On the topic of pressures I found with my 2010TL 6MT, I ran 37psi in the fronts and 33psi in the rear. The reason for this is because of the weight distribution as well as the front bias of SH-AWD. I found tight cornering was much more stable and handling in general was great. I have carried this over to the TLX SH-AWD so I can't compare it with the current car with even pressures but it works for me so I'm not going back.

I'm no expert that's just my experience, perhaps a grain of salt is required.
 
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Filling with air made easy

Today as I got ready for work I remembered I needed to add air to my tires. For whatever reason, one dropped to 27 psi, while the others were 29.

I remembered that the car beeps rapidly when the preferred pressure level has been reached.

I went around to my four mounted tires and applied pressure to each tire till I heard the multi-beeps. When I got into the car to drive off, I was pleasantly surprised to see that all tires were set to 32 psi, when cold. As I drove to work, the pressure increased to 35 after an hour of driving. When I left work to go home, they were all 33 psi, probably because the asphalt was hot.

I love the convenience of not having to measure with a hand-held pressure gauge. :)

 
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