SPRING TERMINOLOGY EXPLAINED
SPRING OR COIL SPRING
The springs carry the weight of the car and allow movement of the wheels, after which they ensure that the car comes back to its normal ride height. The springs are of great influence on the driving characteristics of the car, and if lowered, also on the appearance of the car. Often, the car is lowered using progressive or harder springs, see also below; Hardness / C-value spring;
HARDNESS, ‘C-VALUE’/’SPRING-CONSTANT’ OF A SPRING
The C stands for ‘Constant’
A spring constant is, among other things, expressed in
– Kilograms per centimetre = Kg/cm or also called;
– Newton per millimetre = N/mm
It indicates ‘force per compression’
For example, 50 N/mm = 50 Kg/cm
That means that there is 50 kg of force necessary in order to compress this spring with 1 cm.
If we want to compress this spring with 4 cm, then we need a force of 200 Kg.
The above is expressed in metric/European system. If we want to ‘translate this’ into USA measurements, we need to multiply with 5.6. So:
100 N/mm=Kg/cm = 560 Lbs/in = Pounds/Inch
SHOCK ABSORBER/DAMPER/STRUT
The shock absorber is adjusted to the spring and stroke used. The damper and the spring together form the shock absorber. The shock absorber, as a strut, is part of the MacPherson suspension. They ‘absorb the shock’ by converting the kinetic (motion) energy into heat. They ensure road holding, comfort, safety, the protection of material; if properly adjusted!
BUMP STOP/END STOP/BUMP RUBBER
Work as a ‘pillow’ at the end of the damper stroke. They also provide safety if they absorb the ‘slamming’ of the shock absorber. They are made of a special urethane/rubber compound for maximum energy-absorption.
COILOVER
This is a damper construction in which the spring sits over the damper tube and the tube is fitted with a screw thread. The spring preload is provided by a spring plate with screw thread that turns onto the thread on the damper tube. The preload of the spring is used to adjust the ride height of the car. It is now also possible to change springs to softer / harder / shorter or longer ones.
ANTI-ROLL BAR
Also known as the ‘anti-sway bar’. It is a torsion bar which connects the left and right wheels. Because this creates a connection between the left and right wheels, it helps prevent the rolling of the chassis by means of the torque force in the bar.
CAMBER
Probably the most well-known term. Camber is the angle of the wheels in relation to the road, from a frontal view (in front of the car). Try to imagine a line through the centre of the tread of the tyre. (The so-called ‘centre line’.) At 0º, this line will be perpendicular to the road. (See the green lines.) If these ‘centre lines’ form a ‘V’-shape, then we speak of ‘positive camber’ (red lines).) ‘Negative camber’ occurs when these lines form an ‘A’-shape (blue lines).
CASTER
This is where we look at the car from the side. Now imagine a line that runs through the steering axis. That is the axis around which the front wheels will turn when steering. It usually runs through the upper and lower knuckle balls or through the centre line of the MacPherson pivot points. Figure 3 indicates ‘positive caster’, so the top of this line tilts toward the rear of the car. Figure 2 shows ‘negative caster’. Positive caster is responsible for the self-centring effect, that provides stability when driving in a straight line. This is similar to the front wheels of a shopping cart.
TOE-IN & TOE-OUT / POSITIVE TOE & NEGATIVE TOE
Now, we look at the car from above. Imagine lines in the driving direction, running through the centre of the tread of the tyre.(This refers to the position of the wheels). The red lines show ‘positive toe’, which means the lines cross in front of the wheels (‘A’-shape). The green lines show ‘negative toe’, where the lines cross behind the wheels (‘V’-shape).
