Nitrogen

Maybe you should ask for a transmission flush too.

Given the current seasonal change,

to maintain proper handling,

You should be switching to "winter air" in your tires.

In reply to bentwrench :

Ask for an 80% discount since ~80% of whats in there is already nitrogen...

In reply to bentwrench :

My winter tires have winter air in them.

Woody said:

Science and economies of scale would join forces to preclude anyone from developing a schrader valve stem specific to nitrogen. 

The reason that the dealer will never deflate the tire and refill with good ol’air is because it would take time and effort. It’s easier to not charge you the $100, $99.50 of which is pure profit. 

I went through this once with glass etching. They wanted to charge me $299. I said that I didn’t want it. They said that they did it to every car that comes in. I said too bad. They didn’t charge me for having my VIN etched into the glass, but told me that my glass wouldn’t be “in the registry”. 

I'd have requested they replace all of the glass.  (Knowing that they wouldn't do that, and I'd be headed to a different dealership anyway)

Turboeric said:

outasite said:

Temperature changes do not change tire pressures as much if any using nitrogen. Same valve and you can refill with air. ONE HUNDRED BUCKS IS POOR PROFIT TACTIC. 

The smaller pressure change is strictly theoretical because it relies on dry nitrogen. As soon as the installer slops the bead lube into the tire, the “advantage” is lost. The use of nitrogen in street tires is pure snake oil for profit.

All gasses react that same to pressure, volume, and temperature.  They have to.  It's the pervert rule.  Pv=nRT.  (more accurately, Boyles gas laws)  A nitrogen filled tire will react the same exact way as a tire filled with atmospheric air when it comes to temps.  If you double the temperature (in Kelvin) you will double the pressure.  It doesn't matter if it's Helium, Nitrogen, Chlorine, or CO2.

The real benefit to N2 is that it doesn't contain oxygen or other reactive things that can attack the rubber.  Atmospheric air comes with 21% oxygen that was compressed by a machine that is full of hydrocarbons.

The benefits though don't seem to really matter for most tires though.  I have tires that are 10 years old with plain old air in them and they'll wear bald before they get oxidized. 

Stuart and Eric hit the nail on the head.  One of the benefits to N2 is the lack of moisture.  The Nitrogen extraction process produces 99% pure N2.  With moisture in the tire, you're introducing vapor pressure.  When the temperature goes up and the water evaporates, it exerts pressure.  The temperatures seen by a tire though don't cause much variation in pressure

It's not just the lack of moisture that makes N2 worth using in race tires it's the consistent lack of moisture.  Using my spec. Miata as and example (because I know the numbers off the top of my head); I know that the Falken Azenis that we use as a spec tire at my local track gain about 5 PSI from cold to hot with N2 in the tires.  With air I've seen anywhere from a 5 to 19 PSI gain depending on the amount of moisture in the air.  When I see the really high gains I get visible amounts of water when I bleed the pressure off.

Even with N2 the gain is dependent on ambient temperature.  It's not a fixed 5 psi increase. I actually have a graph the shows the pressure gain with N2 based on ambient pressure.  If there was a consistent amount of humidity from one set of tires to the next then air would be fine.  I'd know the the number was 7 or 14 or whatever but if it's between 5 and 19 then there's no way to start a race with fresh tires and end up with the pressures anywhere near where you want them.

The tire valves are the same apart from the cap, but they actually shouldn't be, exactly: if you're filling with nitrogen, you should have 2 (regular) valves on opposite sides so that you can purge an excess of pure nitrogen through to remove all the air that was in the tire before.

That said, nitrogen filling isn't worth considering for anything but Serious Business race cars. See also:

Nitrogen does help to keep tire pressures more stable.  The primary use is to make a profit and keep the people who can't use a tire inflator from coming back and bitching that their TMPS light is on.  This also helps to avoid a survey, which allows the customer to trash you because they don't like the donuts in your waiting area.  We put nitrogen in every new car during prep, and then tried to make some money off of it.  Profit, a radical concept in business.

In reply to 1988RedT2 :

No, it won't. There are 2 advantages to nitrogen from the dealership point of view: 1) PROFIT! & 2) Not wasting a lot of time dealing with customers complaining about their TPMS lights coming on when the weather changes. Other than that,meh.

In reply to Curtis :

Nugi said:

And I thought getting em to remove their ugly plaques/stickers was the hard part. I always ask for plate frames instead, which then get the dealer name sanded off. 

It wasn't hard or me - when I showed up to pick up my car, they had added dealer plaques to the car.  I told them I hadn't authorized that and had no inclination to offer them free advertising in any event. They said I could take them off with no problem, when I got the car home.  I told them that the car wasn't going home with me until they removed them and that they'd be looking at remedial paintwork or no sale if they screwed it up.

Agree that the ethics of many/most car salesmen are somewhere below whale crap (and you know where that ends up).

PS - if you were buying a new McLaren, OK - nitrogen is a nice thought but still wouldn't make a damn bit of difference to a street driver. Tell them to shove the nitrogen up their ethics.

Curtis said:

All gasses react that same to pressure, volume, and temperature.  They have to.  It's the pervert rule.  Pv=nRT.  (more accurately, Boyles gas laws)  A nitrogen filled tire will react the same exact way as a tire filled with atmospheric air when it comes to temps.  If you double the temperature (in Kelvin) you will double the pressure.  It doesn't matter if it's Helium, Nitrogen, Chlorine, or CO2.

Yep.  This.  And as best as I know water vapor is also a gas and obeys the ideal gas law as long as it doesn't get cold enough to condense.  Seriously, dry air is just as good as Nitrogen for almost everyone but the dealer.

Appleseed said:

In reply to Curtis :

I love me some NDT.

jwagner said:

Curtis said:

All gasses react that same to pressure, volume, and temperature.  They have to.  It's the pervert rule.  Pv=nRT.  (more accurately, Boyles gas laws)  A nitrogen filled tire will react the same exact way as a tire filled with atmospheric air when it comes to temps.  If you double the temperature (in Kelvin) you will double the pressure.  It doesn't matter if it's Helium, Nitrogen, Chlorine, or CO2.

Yep.  This.  And as best as I know water vapor is also a gas and obeys the ideal gas law as long as it doesn't get cold enough to condense.  Seriously, dry air is just as good as Nitrogen for almost everyone but the dealer.

You are correct.  Water vapor conforms to Boyle's gas laws, but it does get murky near the coalescence point.  We did a neat experiment in a physics class where we filled a glass sphere with water vapor and got the pressure to a perfect point that it was still barely vapor.  The gas was transparent.  Then when you hit the sphere with a felt mallet, the sound waves caused awesome patterns of condensive "fog" to form inside the sphere and the pressure gauge danced all around as the water fell in and out of a gaseous state.

This is America. The goal of the dealership is to separate you from as much of your money as they can. It's your job to keep as much of your money as you can.

Nitrogen filled tires are just one of the places where the battle takes place.

I think the green caps look really cool.  Is it okay if I put green caps on my tire stems but fill with plain old air?  Or is that against some law?

bentwrench said:

That sounds like the $300 blinking 3rd brake light my local dealer tried to add on to the purchase price.

My reply was "Im leaving now".

Are those even legal? I seem them here and there, usually on lightly riced hondas and the like

jwagner said:

Curtis said:

All gasses react that same to pressure, volume, and temperature.  They have to.  It's the pervert rule.  Pv=nRT.  (more accurately, Boyles gas laws)  A nitrogen filled tire will react the same exact way as a tire filled with atmospheric air when it comes to temps.  If you double the temperature (in Kelvin) you will double the pressure.  It doesn't matter if it's Helium, Nitrogen, Chlorine, or CO2.

Yep.  This.  And as best as I know water vapor is also a gas and obeys the ideal gas law as long as it doesn't get cold enough to condense.  Seriously, dry air is just as good as Nitrogen for almost everyone but the dealer.

Actually dry air would work in racing applications as well.  It's just that it's cheaper to buy bottled nitrogen than it is ty by bottled dry air.  As far as the water vapor is concerned if you always had the same amount from one set of tires to the next that wouldn't be that big a deal either.  The issue is that when you use compressed air you don't get the same amount from tire to tire and there's no way to predict pressure increase with temperature.  If you're running the same tires for a long time then, as long as the set has the same amount of water vapor then you can compensate but when you go through multiple sets a weekend or even get a weekend and a half out of a set like we do with the Miata it's important to know that you can be consistent with starting pressure from set to set.

As far as I can tell the only performance benefit to nitrogen in street car tires is from the lighter weight of your wallet.

I bought the truck today.  I told the salesman that I wanted air,not nitrogen in the tires and didn't want wheel locks because the key for them would just be something else to lose.  No problem.  With those charges removed & some more haggling, I got an additional $1321 of what had been offered as best OTD price.

mad_machine said:

bentwrench said:

That sounds like the $300 blinking 3rd brake light my local dealer tried to add on to the purchase price.

My reply was "Im leaving now".

Are those even legal? I seem them here and there, usually on lightly riced hondas and the like

Well, you are noticing them, so they must work. Which is the point. I guess?