This is Part 1 of a 2 part general information post from information on the web and from personal experience over a lifetime of vehicle modifications since the 1970’s, to help answer basic suspension questions that some people may have about changing the suspension on their motor vehicles.
Most members on this forum have good knowledge of suspension mods, but many new members and some existing members may wish to modify their suspension and lower their vehicles, but not sure where to start?
Suspension, what type?
Many passenger vehicles have MacPherson strut suspension, this means the shock absorber and spring as one unit, and are a structural component of the suspension, meaning that the strut bears most of the suspension forces and, if the strut is removed, the suspension will not function as they are one unit.
At the rear of the vehicle there could be a coil spring/shock system, others have a separate spring/ and or coil and shock set-up. The coil spring/damper systems are similar to the strut, but do not form part of steering – it only dampens suspension movement and supports the vehicle. With the separate shock and spring system fitted to other vehicles, the shock can be removed and the vehicle can still be driven slowly for a short distance.
Without shock absorbers, a vehicle continues to bounce after hitting undulations in the road or speed humps. The shock absorber dissipates the kinetic energy (mostly through heat) and stabilises body movement. Most shock absorbers work on the principle of oil displacement by a piston (‘s) in a cylinder. The piston has a series of gallery holes/valves that allow the oil forced under pressure to flow through when the piston moves, thereby providing a damping force. With adjustable suspension this flow of oil can be adjusted by a variable valve/and or opening to suit the application you need.
How much can i lower my car with different springs?
Springs store the kinetic energy generated by the wheel’s upward movement and release it by exerting a force in the opposite direction of the spring compression. It’s important to note that this force is proportional to the displacement of the spring and not the speed at which it’s displaced. A softer spring rate results in a comfier ride, but it can compromise the vehicle’s body control, especially during cornering.
A stiffer spring rate results in better body control (or load-carrying ability like in commercial vehicles), but affects the ride quality. The springs secondary function is to support the vehicle-body mass and set the correct ride height. The common types of springs available are coil, leaf and air units. These types of springs can be broken down further in the upcoming paragraphs.
Spring manufacturers usually offer springs that lower vehicles by between 25 to 60 mm. Experts argue that a drop of less than 30mm is not immediately noticeable in ride quality (only visual), and any drop of more than 60 mm can cause problems that will be covered by the questions and answers that follow. A standard drop would be up to 30mm on standard OEM struts, One of the largest suspension manufactures KYB, states that a max of 30mm lowered springs can be fitted to OEM standard struts/shocks, provided that the shock is still in good condition, so that the spring on a strut unit is still under tension when the unit is at full extension, as the vehicle is lowered wheel arch clearance/tire choice/rim offset/and some other component clearances that may come into play, you may need more neg camber/guard rolling/flaring to compensate. Other manufacturers state that a 40mm drop is fine on standard OEM struts, KYB states 30mm, i guess it depends to a certain extent if spring tension is present or not and will the standard strut be damaged over time.
If the spring is not under tension, a special shortened shock is required, this is usually the case when you lower a car by more than 40-60mm+, this varies depending on vehicle. These special shocks have a shorter body, reduced extended length, and modified damping curves (a good example would be the standard struts/springs on the EVO’s)
You could opt for a 60 mm drop at the front and a 40 mm drop at the rear, it can be good to compensate for when the vehicle is fully laden. If a 60+ mm drop-spring were fitted at the rear, there would be a risk of bottoming out under full load, with an end result of permanent damage to the shock.
What’s better progressive and linear, conical?
1/. “Progressive Springs” most common in a daily driver with standard suspension or lowered springs “Progressive springs have unequal distance between each coil throughout the length of the spring. The spring rate will change progressively with the compression of the spring. This allows a single spring to have different spring rates. As an example, a spring may have an initial rating of 4kg, so 4kg may be required to move the spring 1mm, making the spring rate 4kg. For the spring to travel another mm it may require 5.3kg. The spring load “progresses” in weight required for it to compress each subsequent mm. This progression in spring rate is made possible by the varying distances between each coil. These progressive springs are usually found in standard and lowered springs such as EG: Pedders/Lovells/king’s/teins etc.
· Advantages of progressive springs are they become stiffer as they are compressed. Progressive springs allow for a smooth ride over small bumps and have firm characteristics when taking a bit hit such as a pot hole or a hard corner. For street cars, progressive springs are designed to have the balance of being able to offer a smooth ride and good handling.
· Disadvantages of progressive springs are they try to be the single solution for a smooth ride as well as stiff handling but fail and as a result, as you try to strive for a softer ride you worsen the handling characteristics and vice versa. Progressive springs settle for one characteristic over the other making it good all around but not great at any one thing. Progressive springs are not ideal for track use. As the car transfers weight in corners there is more body roll which changes the center of gravity of the car, worsening handling
2/. “Linear Springs” have equal distance between each coil which react the same way under every condition, commonly found in coilover applications such as Pedders extreme XA/Teins/BC racing etc, it's a simple ratio of weight applied to distance moved. Because of this simple equation, linear springs are ideal for racing applications as one can easily predict handling around a track. With a coilover spring rated at 8kg they mean ( if you apply a 8kg load to a spring rated at 8kg, the spring will depress 1mm). If another 8kg load is applied (16kg in total) the spring will depress another 1mm (2mm in total). The result is still a 8kg spring rating even when 16kg is applied, since the spring will still depress 1mm for every 8kg. This is what is called a linear ratio, these springs are a favourite for coilover manufactures because of this predictability.
· Advantages of Linear springs are that they react the same way under every condition, it's a simple ratio of weight applied to distance moved. Because of this simple equation linear springs are ideal for racing applications as one can easily predict handling around a track and Linear springs provide great driver feedback to the handling characteristics of the car.
· Disadvantages of Linear springs are that they are very stiff if too higher Kg load rating is used, although ideal for handling on the track; they provide a rough ride for daily street use, but this car be remedied by ordering a suitable lower Kg rated spring from new or by changing the existing coilover spring to a lesser rated kg spring closer to the standard manufacturers spring specs.
3/.“Conical Springs” should have a mention here as well, these are basically a “tapered” or “Cone shaped end spring”, these fall under the category between a “non linear” or “progressive spring” and can be found in numerous applications, example would be the “Eibach Spring” found on the lancer EVO’s front strut assemblies, while not a true conical design, the top section of the spring is conical in shape and can compress into itself at varying loads, providing better handling than Progressive but not as good as Linear.
· Advantages of this tapered design provide stability to those springs that have a large slenderness ratio. The slenderness ratio defines whether a spring will bend or buckle during compression/deflection. A high slenderness ratio means that the compression spring’s free length is more than 4 times larger in comparison to the outer diameter. In other words, it has a 4 to 1 ratio.
· Disadvantages: basically it’s disadvantage is also its advantage, provides better handling than Progressive springs but not as good or predictable as Linear.
Its length is too long in proportion with its outer diameter and this, by laws of physics, will cause the spring to deform when it travels down to a desired solid height, conical springs have a non-linear rate; because of the variation in the active coils diameters. Tapered springs are characterized not only by their shape, but also by the fact that they are more laterally stable and less liable to buckle than regular compression springs. There is a necessary increase in the applied force to compress a tapered spring due to the flexibility of the larger-diameter coils causing progressive contact with one another.
Some other types of springs/setup’s which need a notable mention are leaf spring and torsion bar, but no need to elaborate about these on this Lancer forum.
Most members on this forum have good knowledge of suspension mods, but many new members and some existing members may wish to modify their suspension and lower their vehicles, but not sure where to start?
Suspension, what type?
Many passenger vehicles have MacPherson strut suspension, this means the shock absorber and spring as one unit, and are a structural component of the suspension, meaning that the strut bears most of the suspension forces and, if the strut is removed, the suspension will not function as they are one unit.
At the rear of the vehicle there could be a coil spring/shock system, others have a separate spring/ and or coil and shock set-up. The coil spring/damper systems are similar to the strut, but do not form part of steering – it only dampens suspension movement and supports the vehicle. With the separate shock and spring system fitted to other vehicles, the shock can be removed and the vehicle can still be driven slowly for a short distance.
Without shock absorbers, a vehicle continues to bounce after hitting undulations in the road or speed humps. The shock absorber dissipates the kinetic energy (mostly through heat) and stabilises body movement. Most shock absorbers work on the principle of oil displacement by a piston (‘s) in a cylinder. The piston has a series of gallery holes/valves that allow the oil forced under pressure to flow through when the piston moves, thereby providing a damping force. With adjustable suspension this flow of oil can be adjusted by a variable valve/and or opening to suit the application you need.
How much can i lower my car with different springs?
Springs store the kinetic energy generated by the wheel’s upward movement and release it by exerting a force in the opposite direction of the spring compression. It’s important to note that this force is proportional to the displacement of the spring and not the speed at which it’s displaced. A softer spring rate results in a comfier ride, but it can compromise the vehicle’s body control, especially during cornering.
A stiffer spring rate results in better body control (or load-carrying ability like in commercial vehicles), but affects the ride quality. The springs secondary function is to support the vehicle-body mass and set the correct ride height. The common types of springs available are coil, leaf and air units. These types of springs can be broken down further in the upcoming paragraphs.
Spring manufacturers usually offer springs that lower vehicles by between 25 to 60 mm. Experts argue that a drop of less than 30mm is not immediately noticeable in ride quality (only visual), and any drop of more than 60 mm can cause problems that will be covered by the questions and answers that follow. A standard drop would be up to 30mm on standard OEM struts, One of the largest suspension manufactures KYB, states that a max of 30mm lowered springs can be fitted to OEM standard struts/shocks, provided that the shock is still in good condition, so that the spring on a strut unit is still under tension when the unit is at full extension, as the vehicle is lowered wheel arch clearance/tire choice/rim offset/and some other component clearances that may come into play, you may need more neg camber/guard rolling/flaring to compensate. Other manufacturers state that a 40mm drop is fine on standard OEM struts, KYB states 30mm, i guess it depends to a certain extent if spring tension is present or not and will the standard strut be damaged over time.
If the spring is not under tension, a special shortened shock is required, this is usually the case when you lower a car by more than 40-60mm+, this varies depending on vehicle. These special shocks have a shorter body, reduced extended length, and modified damping curves (a good example would be the standard struts/springs on the EVO’s)
You could opt for a 60 mm drop at the front and a 40 mm drop at the rear, it can be good to compensate for when the vehicle is fully laden. If a 60+ mm drop-spring were fitted at the rear, there would be a risk of bottoming out under full load, with an end result of permanent damage to the shock.
What’s better progressive and linear, conical?
1/. “Progressive Springs” most common in a daily driver with standard suspension or lowered springs “Progressive springs have unequal distance between each coil throughout the length of the spring. The spring rate will change progressively with the compression of the spring. This allows a single spring to have different spring rates. As an example, a spring may have an initial rating of 4kg, so 4kg may be required to move the spring 1mm, making the spring rate 4kg. For the spring to travel another mm it may require 5.3kg. The spring load “progresses” in weight required for it to compress each subsequent mm. This progression in spring rate is made possible by the varying distances between each coil. These progressive springs are usually found in standard and lowered springs such as EG: Pedders/Lovells/king’s/teins etc.
· Advantages of progressive springs are they become stiffer as they are compressed. Progressive springs allow for a smooth ride over small bumps and have firm characteristics when taking a bit hit such as a pot hole or a hard corner. For street cars, progressive springs are designed to have the balance of being able to offer a smooth ride and good handling.
· Disadvantages of progressive springs are they try to be the single solution for a smooth ride as well as stiff handling but fail and as a result, as you try to strive for a softer ride you worsen the handling characteristics and vice versa. Progressive springs settle for one characteristic over the other making it good all around but not great at any one thing. Progressive springs are not ideal for track use. As the car transfers weight in corners there is more body roll which changes the center of gravity of the car, worsening handling
2/. “Linear Springs” have equal distance between each coil which react the same way under every condition, commonly found in coilover applications such as Pedders extreme XA/Teins/BC racing etc, it's a simple ratio of weight applied to distance moved. Because of this simple equation, linear springs are ideal for racing applications as one can easily predict handling around a track. With a coilover spring rated at 8kg they mean ( if you apply a 8kg load to a spring rated at 8kg, the spring will depress 1mm). If another 8kg load is applied (16kg in total) the spring will depress another 1mm (2mm in total). The result is still a 8kg spring rating even when 16kg is applied, since the spring will still depress 1mm for every 8kg. This is what is called a linear ratio, these springs are a favourite for coilover manufactures because of this predictability.
· Advantages of Linear springs are that they react the same way under every condition, it's a simple ratio of weight applied to distance moved. Because of this simple equation linear springs are ideal for racing applications as one can easily predict handling around a track and Linear springs provide great driver feedback to the handling characteristics of the car.
· Disadvantages of Linear springs are that they are very stiff if too higher Kg load rating is used, although ideal for handling on the track; they provide a rough ride for daily street use, but this car be remedied by ordering a suitable lower Kg rated spring from new or by changing the existing coilover spring to a lesser rated kg spring closer to the standard manufacturers spring specs.
3/.“Conical Springs” should have a mention here as well, these are basically a “tapered” or “Cone shaped end spring”, these fall under the category between a “non linear” or “progressive spring” and can be found in numerous applications, example would be the “Eibach Spring” found on the lancer EVO’s front strut assemblies, while not a true conical design, the top section of the spring is conical in shape and can compress into itself at varying loads, providing better handling than Progressive but not as good as Linear.
· Advantages of this tapered design provide stability to those springs that have a large slenderness ratio. The slenderness ratio defines whether a spring will bend or buckle during compression/deflection. A high slenderness ratio means that the compression spring’s free length is more than 4 times larger in comparison to the outer diameter. In other words, it has a 4 to 1 ratio.
· Disadvantages: basically it’s disadvantage is also its advantage, provides better handling than Progressive springs but not as good or predictable as Linear.
Its length is too long in proportion with its outer diameter and this, by laws of physics, will cause the spring to deform when it travels down to a desired solid height, conical springs have a non-linear rate; because of the variation in the active coils diameters. Tapered springs are characterized not only by their shape, but also by the fact that they are more laterally stable and less liable to buckle than regular compression springs. There is a necessary increase in the applied force to compress a tapered spring due to the flexibility of the larger-diameter coils causing progressive contact with one another.
Some other types of springs/setup’s which need a notable mention are leaf spring and torsion bar, but no need to elaborate about these on this Lancer forum.