What is airing down? To the seasoned off-roader, the term is second nature and a rule always followed. To the newbie, it can be a technique unfamiliar.
Airing down is the process of deflating your tires to a pre-determined, lower pressure. The method allows for the tire to stretch out and create a larger footprint. This larger footprint reduces the pressure from the weight of the vehicle on the ground, facilitating floatation and allowing the tire to mold itself around uneven surfaces on the ground. The bulging sidewalls also let the treaded sidewall portion of the tire assist in the tractive efforts, as well.There is no pre-determined pressure that suits all vehicles, so it will be a tailored fit based on vehicle weight, sidewall stiffness, and sidewall-to-rim ratio. Often the mid-teens is the sweet spot for lighter vehicles, and low 20s to high-teens for heavier ones. Caution must be used when airing down below these sweet spots, however, because the air pressure within the tire carcass is what is forcing the bead against the wheel. The more pressure that is removed from the tire, the less pressure is forcing itself against that bead. Without that seal, the tire bead can jump the lip of the wheel and lose all pressure.
Some off-roaders counteract this issue by the use of beadlock wheels. The beadlock uses a clamping mechanism to mechanically secure the bead of the tire against the wheel. This allows for insurance that the tire bead will not separate in extreme scenarios.
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