Tire pressure obsession

1SLOW1500 · November 29, 2018

Good article. It explains exactly why I'm not going to pay for nitrogen when 78% nitrogen is free.

"Is it worth it? For normal driving, probably not. The advantages, while real, are still really very miniscule."

It's free by me and no issues with pressure. So it worked.

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jadatis · November 29, 2018

4 hours ago, Grumpy Bear said:

I don't use nitrogen in my tires. Cost, availability or as one poster says, 'hassle'. That said the science is sound even if the benefit is minor. Dismissing/denying something because one doesn't understand it or finds it inconvenient doesn't change the science.

True and notable but not the entire story and dangerous. Deflection is also resistance to motion. Ever try to move a wheelbarrow full of dirt with a nearly flat tire? Deflection is also wear not just in general but specific to the area of the tires foot print. By your logic I can inflate my tires in my 68F heated garage I'll be fine when it's -32 F outside. PV=nRT (the basis for the 2% per 10F rule of thumb) says that will be a 20 psi loss of pressure and while it is true that driving increases tire pressure it isn't true it's 20 pounds worth.

What the OP is attempting to understand isn't IF temperature makes a difference or IF there is merit in nitrogen over air but at what point should one be concerned enough to do something about it.

I can only offer my experience. The answer is 'depends'. Look, I monitor my tire pressures every time I get in the truck and then I ask myself the basic question a five year old would ask...does that reading make sense? Tire pressure reads 4 psi higher on the sunny side at noon...yea that makes sense. Is today 'average'? Is this a one day cold snap or unusually hot day or is this a seasonal shift that is likely going to stick around? I use a 5% rule...two or three pounds cold pressure as a point of adjustment IF the conditions seem likely to be around awhile and measured under the same conditions. Like first thing in the morning while the sun is low.

If you make your TPMS reading a habit you can learn allot about your truck/car. If you let it teach you the worry goes away and the education becomes a tool that let's you enhance your experience.

100 degr F temp dropp , tgen rules of thump dont coun anymore, but even then the inside tire temp dont need to to highen 20 psi, and rubber wont reach critical temp at wich it hardens and cracks. Also at those low temps you wont go driving 65mh. So less cicles a second so less heatproduction a second.

About the use of Nitrogen, I made a document in wich I turn it around by claiming that normal air is even better, with all the water in it even.

Better for cooling down of tire in extreme situations.

Will see if I can find it and place the text here.

aseibel · November 29, 2018

20 minutes ago, 1SLOW1500 said:

It's free by me and no issues with pressure. So it worked.

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Yeah, if I had a convenient source that was free, I'd put pure nitrogen in too.

Its just not worth paying the dealer to do it for me when every Kwik Trip and Shell station around me has a free air pump with the gauge. Its so much easier to pull in there than drag out my compressor for 4 minutes of work.

Grumpy Bear · November 29, 2018

3 hours ago, pronstar said:

https://jalopnik.com/heres-the-deal-with-nitrogen-filled-tires-1795659391

How did he not choke on that crawfish? A lot of yea but and if going on there with a dose of BS. Such as:

Also, remember, we live in a big soup of air, so even if your tires are full of nitrogen—and that actually means about 93 percent 95 percent nitrogen—there’s still a whole atmosphere of damp, oxygen-tainted air pushing its way into the tires.

Really, how does that work? Boys, we don't need an air compressor anymore. Just mount your tires and they will fill to the name plate all on their own.

Air is 1.6 times as fast at loosing pressure. That is insignificant? Lack of moisture is a HUGE plus. Pressure stability yes can be maintained with effort. And still 90% of the cars on the road have under inflated tires. So while it can be done...no one IS doing it.

Every good lie and every perfect pitch is ONLY in part true. This one is hugging the bottom.

Capt Bob · November 30, 2018

Well for discussion sake, how many people that bought new tires for their vehicle and got the little green caps with them check the pressure regularly? Observing the obvious, a regular routine of pressure monitoring (the TPMS is meant to enforce this) gains you most of the bennies that N2 use does but as you stated....the majority of car owners rarely do.

Lastly, how does one get the existing air (atmospheric pressure) out of a new tire when filing with nitrogen?

15 Z71 · November 30, 2018

Are the tpms that reliable? How close are they to an actual air gauge?

Cupton · November 30, 2018

21 minutes ago, 15 Z71 said:

Are the tpms that reliable? How close are they to an actual air gauge?

For me it depends on the gauge. I have a couple analog gauges and a couple inflators and all are about 1lb difference from the TPMS with the exception of one. My Joes Racing inflator for my compressor is spot on. If my TPMS says 35PSI so does the guage on the inflator. It also has each number on the guage face (34, 35, 36, 37, etc) which I really like.

aero10 · November 30, 2018

24 minutes ago, 15 Z71 said:

Are the tpms that reliable? How close are they to an actual air gauge?

Pretty much spot on.

One thing I'll add because it worried me for a little bit. I put mine at 35 psi cold (it was close to freezing), but driving down the road on a trip my tires would all easily reach 41+ psi. Well I got concerned about overinflation until I looked at the tire rating. My stock tires are rated for 44 psi cold. So overinflation of the tire isn't going to be an issue if you only air up to 35 psi.

Capt Bob · November 30, 2018

As stated above, I set my pressure to 36 psi using my old gauge and the TPMS will show 35 psi on all tires. I'm thinking (this is my first TPMS) that the monitoring algorithm is based on the thing showing 35 psi. I'm feeling this is close enough for government work.

swathdiver · November 30, 2018

1 hour ago, 15 Z71 said:

Are the tpms that reliable? How close are they to an actual air gauge?

Spot on for a new basic tire gauge in good condition. Also reads the same as my GM Air Compressor's Gauge (made for Hybrid). Tech2 also reads Tire Pressure Sensors independently of DIC with 1/2 pound more precision it seems.

Grumpy Bear · November 30, 2018

1 hour ago, Capt Bob said:

Lastly, how does one get the existing air (atmospheric pressure) out of a new tire when filing with nitrogen?

Same way we use to do it in the hydrogen plant piping. Pressure purge. Using N2 fill the tire to max printed inflation pressure then pull the core and deflate it. Install the core and repeat doing this three times. On the fourth repetition fill to desired pressure and cap. (Note: in a hydrogen plant you actually sample the expelled air with an O2 analyser.) Three however will remove about 97% of the original O2.

Or you can understand that it isn't really the O2 that matters as much as the water in the atmosphere the compressor pumps in. Vapor pressure is what is being controlled not O2. If you get that; the simple act of inflating the tire with dry bottled N2 will reduce the moisture content by a factor or almost 3 if your inflation pressure is 35 psig.

jadatis · November 30, 2018

Prommessed I would search my made document about that filling with normal air is even better then Nitrogen.

Here it is, and I use the same selling instruments as the Nitrogen-lobby does.

So try to de-mith this.

Filling car tires with normal air is better then with Nitrogen.

A. Oxygen, which makes 21% of normal outside air, in volume absorbs more energy to rise a degree in temperature then Nitrogen.

Difference is only 1% , but in selling argument is sometimes mentioned in energy/ mass so Joule/kg.degr. Kelvin and there Nitrogen wins by 13 % . Tires though are filled with a certain volume so that counts .

This selling argument can be de-myth simply by the fact that its untrue.

B. Water in a tire transports the heat more then dry air or Nitrogen-filling ( which is by its production process free of water).

Not for no reason water is used in central heating and cooling system of cars as main substance.

The tire inside will have lower temperature which is better for cooling down the important spots of the tire wich have to keep a low enough temperature to prevent hardening and damage in next bending of those parts.

When incidentally the tire inside gets hotter ( sunshine on tire or severe braking, or high ambient temperature) more water goes over to gas wich highens the pressure inside the tire more then dry gas. Also then more water as gas in tire so even better cooling.

So advantage of water is 2 ways when needed, better cooling and lesser heat production.

Disadvantages of water as oxidation only happen at outside . Tire specialists will confirm that when they remove a tire of the rim , the rim inside the tire is not corroded.

C. When a Truck, transporting flammable substance, is on fire, the little oxygen in a tire will , when exploding ,probably even kill the fire .

In tunnels experiments where done to kill the fire with air current , and it worked, despite the oxygen in it.

D. A normal car tire up to truck tire is not a race-car tire, for which a constant as high as possible contact area, so best grip , is needed to give half a second better round time.

For that reason they are filled with as dry as possible air or Nitrogen.

That this gives low lifetime is not important, and for a normal car tire it is.

Often blowing tires at racing, is seen there as collateral damage, but we don’t want that for normal car tires.

E. A car tire is also not a airplane- tire in which the water can freeze and when landing this can give misbalance , which can lead to tire-failure or accident, when suddenly going from zero to about 200m/h.

The water in a car tire does not freeze that often, and when it does and the car begins do drive , it begins slow and the misbalance is not a big problem . then pretty soon, certainly when on speed the ice is melted to water and problem will be gone.

F. When filled with normal air the user is aware of checking the tires regularly, which takes better care of a saver tire, because regularly filled up to the right pressure and optical checking of the tire .

The illusion that Nitrogen filling makes the tire to loose almost no pressure, which is often exaggerated to 5 times , while in real a poor 2 times and then only in the very beginning, makes the user less caring .

The tire also looses air when hitting pavement so temporary leak between edge of tire and rim, Filling with whatever gas-combination won’t prevent that.

This idea is even stronger when TMPS is used which is often inaccurate , so the user thinks to maintain the right pressure, while really riding with to low pressure for longer time, which can lead to tire damage. Aftermarket sensors for TMPS when screwed on the valve can give leakage trough hole where valve is placed , because of the bending of the valve by centrifugal forces at speed.

G. Filling with normal air is always possible, even with a bicycle- pump, is only to fill up so won’t take that long. When you keep driving with to low pressure , in order to find a place to fill with Nitrogen, you damage your tires. So just fill up with normal outside air, even when the tire is filled with Nitrogen. Then also you don’t need to have the tire refilled with pure Nitrogen by your tire specialist when at home again, not worth the trouble, and normal air is even better then nitrogen because of the water in it.