* Water is the most common choice because it is readily available and inexpensive. However, water can freeze in cold climates, causing the tires to crack and leak.
* Calcium chloride is a chemical compound that is often added to water to lower its freezing point. Calcium chloride also helps to keep the tires from losing air pressure by absorbing moisture.
* Foam is a liquid that is made up of tiny bubbles of gas. Foam-filled tires provide better traction and cushioning than tires filled with water or calcium chloride.
