Variable-assist steering is a power-steering system that varies the effort required to steer the vehicle.

These systems typically require less effort at low speeds or while parallel parking and more at highway speeds. If you’ve ever driven a vehicle with manual steering, you know it is the most difficult to steer when stopped or at slow speeds. Power steering removes that difficulty but consequently may make higher-speed steering too easy. Too easy? You bet. The disadvantages of over-assisted steering include less steering feedback and a greater chance of the driver over-steering when at a high speed, especially in an evasive maneuver.

Don’t confuse this with oversteer, a characteristic of a vehicle. Here I simply mean the act of steering too sharply to avoid a perceived obstacle. Oftentimes accidents occur when a motorist overreacts to a perceived threat and brakes excessively or steers into another vehicle’s path. One near miss in heavy traffic inspires an actual accident nearby. Over-assisted steering simply makes it easier to steer too sharply at higher speeds.

Most power-steering designs use a hydraulic system to assist the driver in turning the wheel. It’s technically a power-assist arrangement because there is typically an underlying direct manual steering apparatus. (This is why you can steer a power-steering-equipped car with its engine shut off, but it’s hard.) Variable-assist steering, as you might expect, varies the amount of steering assist based on input from the vehicle speed sensor in the onboard computer. Its value is in its ability to make stationary steering easier and high-speed steering firmer than could ever be accomplished in a conventional system with the compromise, fixed degree of assist. Variable assist does this all in the same vehicle, seamlessly. 

Information for this was taken from the’s glossary, written by Joe Wiesenfelder.

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Answered by Joe Bruzek on November 10, 2008 in Glossary | Permalink

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