Adjustable Suspension (A Brief Insight)

In this brief article, we will discuss the Adjustable Suspension, the types of Adjustable Suspension and its applications.

What is an Adjustable Suspension?

An adjustable suspension is one in which parameters like Ride height, Stiffness, or Damping can be adjusted by the owner himself.

Why is an Adjustable Suspension needed?

All Suspension systems are tuned by the manufacturer for an average mix of road conditions and usage patterns. The Road condition Mix that the manufacturer takes as reference for the purpose of suspension tuning is arrived at based on data acquired while testing the prototype car over selected routes and conditions that somewhat represent the usage pattern of the car model’s target customer. This Road Mix is arrived at based on years of feedback and issues that past customers reported. It has a lot of assumptions made for practical purposes and need not necessarily be the exact usage pattern of, say, 40% of the potential customers, who could be first-time car buyers.

So it implies that the Factory standard suspension tuning of most car models may not be to the liking of a large number of potential customers who may have likings and tastes that are different from the average mix that the OEM had selected.

This has opened up several possibilities for car and motorcycle enthusiasts who like to tweak and tune the suspension response of their vehicles to their own personal tastes.

What are the Different Types of Adjustable Suspension?

There are basically 2 types of Solid Axles:

  • Manual Adjustable
  • Electronic Adaptive Suspension

Manual Adjustable

Manually adjustable suspensions are usually not available as original equipment from the car manufacturer. Adjustable suspensions are generally available in the aftermarket. Manually adjustable means that you would need to access the underbody in order to make changes to the suspension. The most commonly available adjustable suspension products allow the user to adjust either 

  • Coilover strut ride height or 
  • shock absorber damping, or 
  • Both of the above

Ride height

The most commonly adjustable suspension part is the coilover strut. The coilover strut can be manufactured with built-in provisions that allow height adjustment.

One method of Ride height adjustment is done by the provision of a pre-load adjustment eccentric ring that has steps mating to the bottom plate. On rotating the ring, it causes the shock overall length to expand or contract. The effect is that the pre-load setting of the shock would change and as a consequence, ride height as well.

Another method of ride height adjustment is by the provision of shims or rings that can be added in steps to the shock. In order to facilitate this, the shock mounts provided would be of the removable type.

The adjustable Coilover Shocks available in the market are mostly meant for

  • OFF-roading enthusiasts who like to customize and tune their car, truck or SUV suspension for a particular terrain, or
  • Track-day enthusiasts who want the best handling performance

Damping Settings

A Suspension’s feel and response are often most influenced by the damping settings. The effect of a change in shock absorber settings is almost immediately felt while driving. Adjustable Dampers are a feature that almost no OE car manufacturer offers. One would have to invariably look into the aftermarket for a compatible and adjustable shock absorber/damper.

Adjustable dampers are of basically 2 types, namely “Single Adjustable” and “Double Adjustable”

  • Single Adjustable means that only the Rebound damping settings of the shock can be changed. This is done using a ‘dial’ on the shocks bottom tube with several adjustable steps, without removing the shock absorber from the vehicle.
  • Double Adjustable means that both the Rebound as well as Compression damping settings can be changed

If there are 10 adjustment steps available for bump as well another 10 for rebound, tuning both simultaneously could become rather confusing for those who are not familiar with suspension tuning. As a Pro-Tip: A good starting point for shock adjustment is to set the rebound damping adjuster knob to high damping and the compression/bump damping adjuster knob to fully low. Starting to tune from this point would be easier since this a good reference point that one can experience and remember as the ‘Worst’ setting. Any further setting changes will be easier to compare and improve against the initial reference point.

Electronically Controlled Suspension

An ‘Electronically Controlled suspension’ is the type of suspension that adjusts suspension parameters on its own during driving. In most of the cases, the electronic suspension would also provide user-selectable settings to choose from like ‘Comfort’, ‘Sport’, ‘Sport plus’, etc.

Electronically Controlled Suspension systems are generally only available in the high-end high-performance models or luxury models in a given car manufacturer’s model lineup. Every OEM that provides Electronically controlled Suspension on its car models would have its own proprietary system and a name for it.

Adaptive Suspension is one term commonly used to describe the electronic suspension. Audi’s system is called ‘Predictive Active Suspension’. BMW calls its Adaptive suspension the ’Adaptive M Suspension’.  Mercedes Benz calls their Adaptive Suspension the ‘E-Active Body Control’. General Motors has different systems for electronic control of the suspension depending on the vehicle model. They are called ‘Adaptive Ride Control’, ‘Continuous Damping Control’ and ‘Magnetic Ride Control’.

What are the different kinds of Adaptive suspension?

Adaptive suspensions are of basically 2 major types:

  • Active Damping Control
  • Active Ride Height Control

Active Damping Control

Adaptive Suspensions started appearing initially in the form of electronically adjustable Dampers, called Active dampers. The early versions of Active Dampers had a solenoid valve that was actuated based on a user-selected mode like “Comfort”, “Sport”, etc. Basically, the damping settings would be altered to predetermined values based on the selection and would remain until further selection by the user.

The Electronic dampers later evolved to an active system with its own dedicated Electronic Control Unit (ECU). The system comprised of 

  • Electronically variable valve damping
  • ECU
  • Wheel movement sensors and accelerometers

The ECU received inputs from the wheel sensors by which it would interpret the current vehicle driving condition. Based on this, its internal software would calculate the best setting suited to the given driving condition and accordingly send a signal to the Electronic Dampers. The Electronically variable dampers had a solenoid valve that could be set to multiple 10’s of positions depending on the signal it received from the ECU.

There have been alternative approaches to how the dampers’ damping settings are changed, which affect the speed at which the damper reacts to driving conditions. One of the first such alternative systems was the General Motors “Magnetic Ride Control” (MRC) Electronic Damping system, developed by Delphi Systems. The MRC system’s Damper had an electromagnetic coil inside the piston valve which energized the special Magneto-Rheological metal infused Damping fluid. 

The MR Fluid changed its viscosity depending on the magnetic field applied to the valve. This system has been continually refined and is now in its 4th generation. The system apparently has one of the fastest reactions of approximately every millisecond. The MagneRide has since found wide application in car models across multiple brands like Ferrari, Lamborghini, Ford, and Audi.

Active Ride Height Control

The Active Ride Height Control works in conjunction with the vehicle’s Air Suspension or Hydraulic Suspension System. The more commonly available systems are Air Suspension based. The system consists of an ECU, Air Bellows, Air Reservoir, Valve Block, Air Compressor, and Wheel sensors.

The ECU would receive signals from the wheel sensors as to the vehicle speed and suspension height. Based on these inputs, the ECU would control the solenoid valves of the Valve block to either feed into or bleed out air at each of the Air Springs. The main objective would be to keep the body as level as possible at every driving condition. Other functions would be to lower the ride height during high speed cruising. There would be cabin controls to select ride heights with settings like ‘Off-Road’ and ‘Sport’.

One such example is the GM’s Adaptive Ride Control.

Conclusion

In this brief article, we have discussed the Adjustable Suspension, the types of Adjustable Suspension, and its applications.

In case of any queries or comments, please feel free to ask.

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