All the springs in a vehicle – the torsion, coil, or leaf spring – are designed to compensate for any road surface irregularities, support added weight without sagging excessively, and maintain a suspension system at a predetermined height.
The coil windings’ geometry and the wire’s diameter are used to define the spring’s damping performance.
The overall design elements have a particular function but collectively ensure the vehicle will be a comfortable ride with precise handling and load-bearing capability. It is these three issues that are the foremost concern for many customers.
• Leaf Springs
Steel multi-leaf spring is a widely used spring design in vehicle suspension systems that have been around for decades. Leaf springs offer many advantages, with the most pronounced being that they work effectively as springs. Furthermore, they can be affixed to the axle, allowing it to be directly attached to the car chassis. The mono-leaf spring is used in some applications.
Ideally, leaf springs are a common feature in trucks with solid drive axels. However, a transverse leaf spring can be added to an independently suspended rear axle forming a robust, lightweight rear suspensions system that is a feature in many performances road cars.
Leaf springs can be tuned to accommodate different loads and meet ride control requirements. This is achieved by altering the spring leaves’ widths, thicknesses, numbers, and lengths.
Moreover, leaf springs act as rebound dampeners, resulting from the friction the leaves generate when they rub against each other. A sturdy plastic unit can be used in place of a conventional steel spring to lower the unsprung weight and mitigate corrosion attributed to road salt and other elements.
• Torsion Springs
Torsion-bar suspensions have been a standard in vehicles with the SLA (Short-Long-Arm) suspensions system. The torsion bar is a round rod roughly four feet in length designed to twist under the weight applied to the suspension system. A torsion bar is manufactured with a clockwise or counterclockwise twist build that ensures a particular torsion bar only fits the vehicle’s side it is designed for, which is a performance safety strategy.
Robust, compact, and lightweight are some of the top benefits of the torsion bar suspension system. A threaded screw adjustment controls the torsion bar tension, allowing for these bars to be used in fine-tuning a car’s suspension height. Also, the bars can be attached to the lower or upper control arms, increasing the design’s adaptability.
• Coil Spring
To better understand what a coil spring is and how it works, it is best to visualize it as a long and thin torsion bar that is wound to form a coil. The bar is more of a thick wire that twists when the spring compresses and extends, which in principle is how a torsion bar works.
Coil springs take up a small space, which can be used in different suspension designs, including independently sprung rear axles, MacPherson strut, SLA suspension systems that use coil-over-shock absorber, or a spring configuration solid-axles with trailing arms.
Coil springs must be replaced in pairs because it ensures the vehicle has precise handling and alignment.
Most modern vehicles use coil springs in the MacPherson strut design variations, which feature variances in the overall coil wire diameter, wire gauge, number of wound coils, and spring height (length) to determine its characteristics.
Coil springs can sometimes be designed with a variable rate spring, which increases load-bearing capacity during compressions. The variable-rate coil springs are standard in trucks with heavier load-bearing chassis configurations.
How Springs Work
Overall, springs are meant to cushion a vehicle for a comfortable ride based on the sprung-to-unsprung ratios. For instance, a farm wagon without springs has a 100% unsprung weight. Installing springs between the axels and chassis gives the wagon roughly a 90% sprung-to-unsprung ratio, representing its chassis weight and an axle-to-wheel weight of 10%.