Nitrogen vs Air in Tyres

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Nitrogen molecules have a lower thermal conductivity than normal air and because of this may keep the tyre surface hotter for longer.

This is mainly an issue with race cars where the tyres are run at high tyre pressure for extended periods of time.

For passenger car tyres this effect is minimal. In fact, nitrogen-filled tyres may take longer to warm up and reach the desired tyre pressure especially if the car has been standing in cold weather. Nitrogen in tyres will keep a constant tyre pressure better than air-filled tyres as there is no moisture content to leak out of the tyre whilst it heats and cools during driving.

This should increase the life of the tyres and better fuel economy. Nitrogen filled tyres have demanding environments to show-off their performance as compared to air-filled tyres.

How do I put nitrogen in a car tyre?

Nitrogen can be added to a tyre or multiple tires in two ways, either by using a nitrogen inflator or by converting the dry air pressure in the tyres to nitrogen with an onboard nitrogen generator. The latter method is more common as it is more cost-effective. There are several companies that sell generators that will work with any vehicle. Nitrogen generators use an adsorption/desorption process to remove the oxygen from the ambient air and replace it with only nitrogen.

Is nitrogen better than air in tyres?

For racing cars, this is probably the best way to go. For passenger car tyres, probably not. For road-going cars, using branded tyres like Michelin, there is very little difference between nitrogen vs air in terms of the tyres themselves and gas mileage. The benefits come from less tyre heat build-up due to a lower thermal conductivity and low tire pressure loss and longer tyre life due to a lack of moisture as opposed to air tyres. This means they run cooler and the temperature changes gradually. The temperature rise is slow due to reduced thermal conduction, which means the heat generated is less as compared to that in case of air. There's a controversy whether nitrogen will avoid wheel rust and rolling resistance. The rolling resistance is however, debated in trailer tyres and not in cars.

What are the disadvantages of nitrogen-filled tyres?

The main disadvantage of nitrogen-filled tyres is the initial cost of setting up a system to fill your tires with nitrogen. The other disadvantage is that, if you face pressure loss in a tire of nitrogen, means you will not be able to top it up with compressed air. You would need to go to a specialist tyre maintenance garage with a nitrogen refilling station. Some systems allow for a small amount of compressed air to be mixed with the nitrogen tyre inflation pressure in order to make topping up easier. Other disadvantages are slow leaks, valve leaks and other mechanical leaks.

Is there a difference between air and nitrogen in terms of fuel economy?

There is no real difference between the two gases when it comes to fuel economy. Regular air and nitrogen have the same molecular weight and therefore create the same drag on the new car. Because the optimal air pressure for fuel economy has not been reached, there is no difference in miles per gallon. Since nitrogen tyres tend to run at a hotter temperature, the tyres may inflate slightly more than air-filled tyres and therefore create slightly more drag on the vehicle but only by a fraction of a km per litre

Where can I get nitrogen to fill my car tyres?

There are a few places where you can get nitrogen to fill your car's new tyres. The most common place is at a garage or tyre retailers. They will have a nitrogen refilling service station and will be able to top up the right tyres for you. There are also a few companies that sell nitrogen generators that will work with any vehicle. These companies also sell refill cartridges so you can keep your tyre pressure-filled with nitrogen without having to go to a garage.

What other gasses can be used in car tyres?

Other gases that can be used in inflating tyres are argon and carbon dioxide. They both have a lower thermal conductivity than air, making them ideal for race cars tires. However, they are not as common as nitrogen as they are more expensive to use. Argon is also a bit harder to find than dry nitrogen. Carbon dioxide is mainly used in agricultural applications as it helps to retain and support moisture in soil.

What pressure should my car tyres be?

The tyre pressure of your car is dependent on both the weight of the vehicle and its intended purpose. Most passenger cars run at around 32-36psi, whereas race track cars can run at anywhere between 12 and 55psi for better ride quality. The higher psi you go, the more fuel-efficient your car becomes but it will also be less forgiving under braking and cornering. Correct air pressure dramatically changes the lifespan of your tyres.

How do I know when my tyres need to be topped up?

You should always keep your tires inflated with air before the tyres become completely flat as this will cause irreparable damage to the tires and may cause any serious injury or accidents. However, once the tires have been fully deflated, there are a number of ways you can tell when it is time to add some air or nitrogen right back into the tires. You should look for the signs below when you are checking your tyre pressure.

Tyres are not holding their shape and are starting to bulge out
Tread is looking thin and worn
There is a notable difference in the tyre pressure between the front and rear tyre pressure
The car pulls to one side when you are driving

If you notice any of these signs, it is time to take your car for a tyre rotation and proper inflation pressure. You can also use a tyre pressure gauge to check the tyre pressures regularly and make sure the tyres are within the recommended range.

How much does it cost to fill my tyres with nitrogen?

Any tyre shop that provides this service will charge per tyre and they can alter between the different gasses such as air, carbon dioxide, and argon. The cost is usually around $25 to $30 per tyre for nitrogen inflation pressure but this may vary depending on the location. There are also a few companies that sell nitrogen generators and refill cartridges, which can be cheaper in the long run.

What is a nitrogen generator?

Nitrogen generators are devices that turn atmospheric air into pure nitrogen and these systems use an electrical current to separate oxygen molecules from other gases and water vapour in the air. This oxygen removal process leaves behind dry gas. This high-purity nitrogen gas doesn't support any contaminants or moisture inside the new tyres. The generators come in a variety of sizes and can be used with any vehicle tyres. They are also portable so you can take them with you when you travel.

Looking to recycle car tyres? The NSW Department of Environment has some handy tips.