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Discussion Starter #1
I run 42 psi in the Goodyear OEM tires. Gauged when cold. It is so hot in this area, ambient temps 108/111 degrees fahrenheit, that the DIC tells me the pressures are 46/49 psi after 10 miles of 65 mph freeway driving. When cold the DIC reading is fairly accurate when checked against an electronic pressure gauge.
What pressure would you run in these conditions when checked with the tires at 72 degrees?
 

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The maximum pressure for the Goodyear OEM tires is 51 psi, so you are not exceeding that. However, the DIC units on my Volt read about 1.5 psi lower than the gauge pressure, so you may be pushing it. If it were me, I'd probably reduce the DIC-indicated pressure to about 44 psi.

I read somewhere that filling the tires with pure nitrogen, as they do at Costco, reduces the pressure variation with temperature because water vapor, which has a larger expansion coefficient, is excluded.
 

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I'd run them at whatever pressure you want between the door placard pressure and the maximum 51 PSI ambient air temperature pressure. I've had these tires running at 56 PSI in 100+ degree temperatures while running at 80 MPH across western Kansas. Don't worry about uneven tread wear as a result - radial tires don't bulge like the old bias ply tires did. I ran a set of these tires at 50 PSI cold for 40,000 miles and had even tread wear until I had to replace them for dry rot.

Whatever you do, do NOT run them below the door placard pressure as this will significantly increase rolling resistance and put excessive stress on the sidewalls.

Oh, invest in a good tire pressure gauge - don't depend on the TPMS numbers.
 

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Discussion Starter #4
The maximum pressure for the Goodyear OEM tires is 51 psi, so you are not exceeding that. However, the DIC units on my Volt read about 1.5 psi lower than the gauge pressure, so you may be pushing it. If it were me, I'd probably reduce the DIC-indicated pressure to about 44 psi.

I read somewhere that filling the tires with pure nitrogen, as they do at Costco, reduces the pressure variation with temperature because water vapor, which has a larger expansion coefficient, is excluded.
I use an electronic/digital gauge as stated in my original post. They are very accurate. The DIC usually reads within 1 psi of my gauge when checking cold tires so apparently it is fairly accurate as well.

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I know next to nothing about tires, other than what my brother the tire expert has told me, and that was mostly about the materials used in and the construction of the tires. (And how most people get flats). With that forewarning, I'd probably back off by a couple of psi if it's that hot. In fact I might even drop down to 38 psi cold, especially if I was going longer distances. I just don't see any advantage in pushing the inflation that hard.

For me the difference in cold and running tires is 3 psi, maybe 4 psi max. Not all that different.
 

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Oh, invest in a good tire pressure gauge - don't depend on the TPMS numbers.
I have found that my TPMS sensors are very accurate, match the quality tire gauges, and the crappy cheap tire gauges are almost always off (I've since pitched them). My only complaint is while filling tires, it takes a minute or two for the TPMS to react, so. Good tire gauge will give you instant gratification rather than sitting there for 5 minutes or so waiting for a number to maybe change, maybe not, so you add more, wait, add more wait, then the TPMS tells you that you are 5 psi over...
 

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There was a discussion a while ago and it seems the variation in digital display pressure is due to altitude. I'm guessing you live at a high elevation. Not at sea level.
 

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Discussion Starter #8
There was a discussion a while ago and it seems the variation in digital display pressure is due to altitude. I'm guessing you live at a high elevation. Not at sea level.
Thank you. But there is almost no difference between my digital gage and the DIC at my altitude of 1,600 feet. My question was basically asking what you all run as a starting/cold tire pressure when dealing with extreme ambient temps, 108 degrees and up. After just a few miles at 65 mph I am seeing front tire pressure approaching 50 psi.

I think the folks suggesting I lower my starting/cold psi reading a couple of pounds are giving good advice. That is what I am going to do.

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hpleog: Have a look at http://www.popularmechanics.com/cars/how-to/a3894/4302788/ .

This Popular Mechanics article says that (a) nitrogen diffuses through rubber more slowly than does oxygen and (b) it suppresses moisture that leads to big pressure variations with temperature. These are both good things to have.

The video you referenced seems to assume that if you get your tires filled with nitrogen, you must never put in your own air and you have to keep coming back for more. It also seems to assume that if you put in nitrogen, you never do a pressure check. That isn't at all how I would do it. Adding a psi or so of ambient air to a 42 psi tire will not change the gas inside much, so I'd feel free to do so. All Volt owners have their own air pump.

That being said, I don't think I would pay for a nitrogen fill, but if Costco or some other place does it for free, I'd certainly go for it.

This brings up an interesting idea, though. Why not have an in-line chemical dryer that connects between the air pump and the tire, so that one can reduce the moisture inside the tires? I see that one can buy an in-line dessicant dryer that goes up to 60 psi for $4.59 on eBay.
 

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Smarti has it right. However, you need to adjust your cold pressure with seasonal changes in temperature. I run 42 psi cold. Forget what it does as the tires warm. Nitrogen is pretty much a scam in car tires. It's used in high performance aircraft to prevent a fire if a tire blows. The Concorde's tires were filled with nitrogen. I currently am running General Altimax RT-43's and they lose literally no pressure. Some tires lose more, some less, through the rubber. I don't depend on the DIC for setting pressure. My favorite gauge now is a CyclePump inline analog gauge. (www.cyclepump.com). You attach it to the valve stem, then fill thru a fitting on the gauge. There's also a buttom to release air. Very convenient as you can observe the pressure while filling. I won it at a motorcycle rally.
 

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I keep mine at 40psi cold (per my tire gauge), but the TPMS shows 38 cold and will rise to around 40 or 41 after driving 10mi or so on the freeway. My max sidewall psi is 44.
 

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Dont laugh but I go to my local stewarts for their digital station. I put in 41 but vary through out the year here in the north east but in the summer now the intent is to run 41 cold and at 43 hot as it seems to go up about +2 for my typical driving patterns. I would go higher but the ride is harsher. But the DIC reading is near spot on for my 2014 matching the stewarts pressure gauge. But after the fill ding, I do another apply to fill/top off to same target as it seems to kind of top it off reaching target pump pressure settomg. This later technique seems to get my DIC reading to match all the time for some odd reason the stewarts pump digital meter. Maybe the initial ding by the stewarts digital meter meeting the target pressure is off by 1 psi. Anyway this works for me. And yes I go to the same stewarts pump all the time. Im sure they can vary by station.
 
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