Regearing is not a requirement when lifting your vehicle to install larger tires. Your vehicle will continue to operate with factory gearing, but may feel more sluggish during acceleration with larger tires installed. The act of regearing refers to swapping out your axles ring and pinion gears to use ones with a different number of teeth which will calculate out to a different rotation ratio (ie. changing a stock 3.07:1 to a 4.56:1). This change in the ratio will help to alleviate strain on the drivetrain allowing your vehicle to more easily rotate the larger mass of an oversized wheels/tires.