Now we have looked at various types of suspension, let’s take a look at the component parts of these systems. From this you will begin to see similarities between the many different suspension set-ups. Firstly let’s look at springs. Many people would say these are the heart of any good suspension. There are basically three types of spring fitted to cars and trucks, the coil spring, the leaf spring and the torsion bar.

The coil spring is simply a steel bar that is formed into continuous coils. These coils compress to give support to any load applied to them. There are two basic types of coil spring, the constant rate spring and the variable rate spring. The constant rate spring is the simplest; all the coils in this type of spring are spaced evenly throughout the length of the spring, see fig 7. The distance between the each coil is referred to as the pitch and the angle at which each coil lies is called the pitch angle. So why do we need to know these terms, well it will make it easier to understand how a variable rate coil works. The variable rate coil achieves, well, its variable rate via a change in pitch angle through the length of the spring. This will give us a spring that has areas where the pitch of the coils is less than in other areas of the spring. This means the coil will function differently from the constant rate coil. In the variable rate coil as a load is applied the coils with less pitch will begin to touch each other, this effectively reduces the overall length of the spring increasing the springs rate. For those of you who are still wondering what we are waffling on about, the springs rate can be looked upon as its strength or ability to resist the load it is put under. Variable rate springs are often used on vehicles that do a lot of towing.

Leaf springs are usually made up from several flat lengths of steel formed into a bow shape. It is this bow that gives the spring its springiness. Each flat piece of the spring is called a leaf, hence the name leaf spring. Most leaf springs are made from 4 to 6 individual leaves, although some vehicles, such as the C4 and later Corvette, have what is known as a mono leaf, just a single leaf. In the case of the Corvette this mono-leaf was made from Carbon-fibre, and is mounted transversely or across the car. In fig 8 you can just see the end of the transverse spring, from a 1990 Corvette, sitting in its bush. Leaf springs are usually mounted to the vehicle using long bolts; these bolts usually pass through rubber bushes and mounting plates at the front and rear of the spring.

So now we know more about springs and how they function, what are the tell tale signs of spring failure. The typical signs of spring wear are a vehicle that appears to sit low and or bottoms out regularly. You may also find that the vehicle ‘wanders’ or drifts to the left or right whilst driving. This is more obvious if it is the front springs that are worn. With worn front springs you will also notice the nose of the vehicle dive more than normal during braking. The final and probably the most noticeable symptom, of spring wear, is the lack of control and excessive lean the vehicle has during cornering. Whilst we have put these symptoms down to spring wear, anyone or more of the above could also be caused by a broken spring. In many ways a broken spring is more problematic and dangerous than a spring that is simply worn out. A broken spring is unpredictable, you never know how it will behave and they can cause sudden changes in vehicle handling. Now as much as we hate going against popular belief, there is only one way to solve the problem of worn or broken springs, and that is to have them replaced.

Remember that if you are planing to change the ride height of your vehicle by more than two or three inches you may find that you will need to replace your shock absorbers as well as the springs. If you are looking to upgrade your springs so you can use your vehicle for towing then you may want to consider asking your parts supplier for Cargo Coils, see fig 10. These are normally a stock sized coil but made in a variable rate design. These Cargo Coils are able to deliver a smooth ride with the added ability to withstand the riggers of towing. Once you have decided to replace your coil springs it is worth checking to see if they have insulators fitted, see fig 11. These are small doughnut shaped rubber discs that usually sit in the top of the coil helping to reduce any noise and vibration caused by the spring. If the insulators are badly worn or split it is well worth replacing them, it is this attention to detail that can make the difference between a good and a bad job. Now for some final words of advice concerning the fitting or removing of coil springs, always use a spring compressor. This simple tool does exactly what the name implies and compresses the spring. This will allow you to remove your old springs and fit your new springs with ease. We have heard terrible stories of people trying to remove coils without a compressor and ending up with broken bones. We heard of one person actually being knocked unconscious for over two hours after being hit in the head by a low flying coil spring.

Fig 11. Coil spring insulator

Fig 15. Polyurethane bush set