Tech Talk: Vehicle Stability Assist

When you press your brake pedal, the brakes on all four wheels are applied to stop your car. That’s a big responsibility! Brakes have been tasked with this since the inception of the automobile. With the introduction of Vehicle Stability Assist (VSA) your brakes have been bestowed extra responsibility. If you live in New England chances are you’ve seen the stability light blink as you accelerate in slippery weather. It flashes to indicate a loss of traction at the wheels. Speed sensors are attached to each wheel. If the speed difference between wheels becomes too great VSA slows the wheel that is slipping and spinning. It allows the tire a reasonable amount of time bite into the surface you’re driving on. Power from the engine likes to take the easy way out, and having no traction invites power to flow. Resistance is created slowing the wheel to regain traction. Engine power flows to the opposite wheel. The brakes are used to help split power evenly and control excessive wheel spin.

The friction coefficient of snow changes with temperature. When the temperature is near zero the snow and ice molecules are rigid. As the temperature nears 32 degrees these molecules relax. The weight and contact of the wheel rolling on snow produces a thin layer of water. This gives snow a “greasy” feel. I was astounded to find that a temperature difference of 32 degrees can make snow FIVE times more slippery. This is not an excuse to drive faster when it’s absolutely frigid, but you’re likely to have slightly better snow traction. If the temperature rises, the route you drove this morning could prove tricky a few hours later. It is inevitable that even the most careful driver will experience the absence of friction.

With the variability of road conditions, you can never be absolutely certain the car will stay on its intended path. Fortunately, the VSA module is being fed information about your cars position from a variety of sensors. Steering angle, chassis roll, and lateral acceleration (sliding) data streams are updated dozens of times per second. If the vehicle becomes unstable and the parameters are exceeded VSA will activate. The brakes on each corner of the vehicle are applied strategically depending on the severity and skid direction. When VSA activates, your only requirement is staying calm and steering accordingly. Single vehicles accidents have been reduced 30% since the introduction of stability systems. Keeping your brakes properly lubricated and adjusted is essential for smooth stopping and VSA operation. Come see our professionals in Honda service if you have any concerns or want to give your brakes a refresh. If you have car technology questions or topics you would like me to cover I would invite you to send me an email to Reid@TheAutomaster.com.

Happy Travels!

Reid

 

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