The forces generated by a vehicle in motion are
extremely complex and very difficult to control, as they occur along
many different axes.
In the architecture of a suspension system, the purpose of the springs is to support the weight of the vehicle and to absorb the stresses imparted by the road surface, keeping the vehicle body in the correct attitude with respect to the road. Springs are continuously subject to movements of compression and rebound.
Springs are subject to wear: over time, continuous stress leads to
fatigue and causes them to lose their elasticity. Springs gradually lose
their ability to return to their original size as the result of
stress-induced fatigue. Used springs will therefore be longer than new
ones.
There are many good reasons for monitoring the condition and
functioning of the springs in your vehicle's suspension, and changing
them as soon as fatigue is detected. For a start, springs in good condition ensure easier driving and better directional control.
They also extend the working life of the shock absorbers and other
suspension components (including the tyres) and maintain the correct
clearance between your vehicle and the ground.
When replacing springs as the result of fatigue or breakage, always replace them in right and left pairs<. It is also best to replace the shock absorbers at the same time (again right and left together).
As is the case with shock absorbers, replacing just one spring will
cause imbalance between the wheels concerned, leading to significantly
poorer braking and handling.