Shock Absorbers and Stopping Distance

Springs and shocks control the motion of each wheel of a car. Springs enable the suspension to move up and down over bumps and imperfections in the road. Shocks absorb and dissipate the energy from that motion. Without shocks the car would continue to bounce on the springs after hitting a bump. Having worn shocks is somewhat like that.

Good shocks are important not just for passenger comfort, but also for safety. We have often heard that shocks keep tires in contact with the road, which is only partially correct. How often have you seen tires not in contact with the road? Even worn shocks won't cause your tires to dribble off the ground.

The full reason is that, for a given set of conditions, it's the amount of downward force which varies a tire's traction. Good shocks keep the tire in optimal contact with the road, enabling consistent maximum traction and shorter stopping distance.

See Wikipedia for more.

Tests carried out by Monroe Shocks (a leading manufacturer) indicate worn shocks can increase stopping distance from 60 mph on the order of about 10 feet, which is about 7% to 9% (most cars stop from 60 mph in about 110 to 130 ft).

Here's a good animated site by Gabriel (shock manufacturer) that explains the effect of shock and strut wear (http://www.checkyourshocks.com/).