COILOVERS: What are you actually paying for?

COILOVERS: What are you actually paying for?

No matter the price, coil overs all contain a spring and a damper, they all adjust ride height, and plenty of them have adjustment knobs.

So, what actually separates a budget coilover from a high-end motorsport damper?

The Spring

Spring rate determines how much force is required to compress the spring. Increasing the rate reduces suspension movement but also changes how the tyre interacts with the road.

A good coilover package isn't simply fitted with the stiffest springs possible. Spring rates should be selected around:

•Vehicle weight
•Suspension motion ratio
•Aero load
•Tyre choice
•Intended use
Stiffer isn't automatically faster. Too stiff and the tyre can struggle to follow an uneven surface, reducing mechanical grip.
The Damper

The damper controls how quickly the suspension moves by forcing oil through carefully designed valves.

Better dampers can provide more precise control of:

•Rebound  - suspension extending
•Compression - suspension compressing
•Low-speed movement - primarily body control
•High-speed movement - bumps, kerbs and sharp inputs

The objective isn't simply more damping. It's producing the right damping force at the right shaft velocity. Two dampers can both have “20 clicks of adjustment” and behave completely differently. Damper force changes depending on how quickly the piston is moving.

•Low shaft speeds are associated heavily with controlling pitch, roll and weight transfer.
•Higher shaft speeds occur during sharper suspension inputs such as bumps and kerbs.

Essentially, higher-end dampers allow engineers to shape this force vs velocity curve far more precisely.

Construction

Higher-end dampers may use larger pistons, higher-quality seals, better bearings and greater oil volumes.

You'll also encounter:

•Twin-tube: an inner working cylinder surrounded by an outer reservoir.

•Monotube: piston and oil contained within a single main cylinder, typically separated from the gas charge by a floating piston.

Neither design is automatically superior. What matters is how effectively that architecture has been designed and valved for the application.

Adjustability

A basic adjustable coilover may have a single adjuster that changes rebound- or affects compression and rebound together.

More advanced dampers can independently adjust:

•1-Way: Usually rebound
•2-Way: Compression + rebound
•3-Way: High/low-speed compression + rebound
•4-Way: High/low-speed compression + high/low-speed rebound

This gives you much greater control over the platform. But there's a catch: A coilover is only as good as how it’s been set-up.

Heat and Consistency

Dampers turn suspension movement into heat.Every time the piston moves, oil is forced through the valving. During sustained track driving, this generates significant temperature. As temperatures change, so can the behaviour of the damper. This is where oil quality, gas pressure, oil volume, seals and reservoir design become important.

A high-end damper isn't just expected to work well for one corner. It needs to behave consistently throughout the session. Remote reservoirs can also increase fluid/gas capacity and help packaging and thermal management.

Suspension Travel

Lowering the car doesn't automatically improve handling. Reduce ride height too far and you can reduce available bump travel. Once the damper reaches the end of its travel, or heavily engages the bump stop, your effective wheel rate can increase dramatically.

A properly developed coilover package considers:

•Bump travel
•Droop
•Bump-stop engagement
•Damper stroke
•Intended ride-height range

A £4,000 coilover set sitting on its bump stops can still handle terribly.

What Should You Buy?

ROAD / FAST ROAD
You don't need endless adjustment. Look for sensible spring rates, decent ride quality and dampers that still work properly when the car is lowered.

ROAD + TRACK
This is where better damping starts to pay off. Consistency when hot, usable adjustment and the option to change spring rates are worth spending money on.

DEDICATED TRACK CAR
Rebuildable and revalvable dampers start to make sense. Independent compression and rebound adjustment gives you more scope to tune the car around different tyres, circuits and spring rates.

RACE CAR
Repeatability matters. If two clicks of compression made the car better yesterday, you need those same two clicks to produce the same change today. Damper dyno data, tightly matched units and proper technical support become part of the setup process.

Don't buy the most adjustment. Buy the best damper you can justify.

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