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Damping Explained — Compression, Rebound, Digressive vs Linear Pistons

Posted by Dežru Suspension Engineering on Nov 23rd 2025

Introduction

Damping is the heart of any suspension system. Spring rates determine how much force is required to compress the spring — but shocks determine how fast and how smoothly the suspension moves.

Without damping, your car would bounce uncontrollably.
With poor damping, your car handles unpredictably.
With proper damping, your car gains grip, comfort, and stability.

This article breaks down damping in simple, accurate terms — tuned specifically to how Dežru coilovers are engineered.

What Is Damping?

Damping is the shock absorber’s resistance to movement.

When the suspension compresses or rebounds, oil is forced through valves, ports, and shim stacks, generating controlled resistance.

Damping controls:

  • Body roll

  • Brake dive

  • Acceleration squat

  • Mid-corner stability

  • Ride comfort

  • Tire grip

  • Heat buildup

Springs hold the car up.
Damping makes the car drive well.

Compression vs. Rebound Damping

Damping has two primary directions:

Compression Damping (Bump)

This is resistance as the suspension compresses — when the wheel moves up into the body.

Compression controls:

  • Harshness over bumps

  • Brake dive

  • Weight transfer

  • Bottoming resistance

Too soft → car blows through travel, feels sloppy
Too stiff → harsh, skips over bumps, loses grip

Rebound Damping

This is resistance as the suspension extends — when the wheel moves down away from the body.

Rebound controls:

  • Spring return speed

  • Oscillation control

  • Weight transfer on corner exit

  • Grip over uneven surfaces

Too soft → floaty, uncontrolled, multiple oscillations
Too stiff → tire can’t follow the road, traction loss

On most cars, rebound does more “work” than compression for handling feel.

Low-Speed vs High-Speed Damping

Speed here refers to shock shaft speed, not vehicle speed.

Low-Speed Damping

Low-speed events are body movement events:

  • Cornering

  • Brake dive

  • Acceleration squat

  • Pitching

  • Roll

Low-speed damping determines:

  • Response

  • Sharpness

  • “Sporty” feel

  • Chassis control

High-Speed Damping

High-speed events are sharp impacts:

  • Potholes

  • Cracks

  • Curbs

  • Expansion joints

  • Ruts

High-speed damping determines:

  • Harshness

  • Comfort

  • Impact absorption

  • Tire stability

A properly valved shock separates these two regions cleanly.

Linear vs Digressive Pistons

Dežru uses multiple piston philosophies depending on the product line.

Linear Pistons

Used in:

  • Spec-S

A linear piston produces a damping curve where force increases proportionally to shaft speed.

Characteristics:

✔ Predictable
✔ Smooth transitions
✔ Excellent for mixed-use
✔ Comfortable yet controlled

Linear valving is ideal for:

  • Daily driving

  • Spirited back-road driving

  • General track use

  • Longer suspension travel

Digressive Pistons

Used in:

  • Spec-R
  • Spec-RS (on some platforms)

A digressive piston has:

  • High low-speed damping

  • Softer high-speed damping

The damping curve “flattens” at higher shaft speeds.

Characteristics:

✔ Sharper steering
✔ Better platform support
✔ More “planted” initial feel
✔ Softer over bumps at speed

Digressive valving is ideal for:

  • Autocross

  • Smooth tracks

  • High-grip tires

  • Cars needing more initial roll resistance

Why Dežru Uses These Piston Types

Your lineup is designed around chassis behavior:

Spec-S  → Linear

These platforms are optimized for:

  • daily comfort

  • composure over rough roads

  • stable roll behavior

  • predictable dynamics

  • long-stroke travel

Linear valving + fixed-length shocks maintain excellent drivability.

Spec-R / Spec-RS → Digressive

These platforms are optimized for:

  • faster response

  • more initial bite

  • quicker weight transfer

  • higher grip situations

Digressive pistons shine where low-speed damping is king.

How Damping Works in a Fixed-Length Dežru Coilover

Since Dežru does not use adjustable lower brackets:

  • damping always stays in the correct stroke window

  • valving is never forced into a “dead zone”

  • bump/droop travel remains consistent

  • heat control is better

  • tuning repeatability is higher

Adjust-height-via-perch systems eliminate the biggest risk of bad damping behavior:
changing shock length past the designed valving range.

This is one of the biggest engineering advantages of your system.

How Adjusters Work 

Rebound-adjustable shocks primarily change low-speed rebound, affecting:

  • corner entry

  • mid-corner stability

  • weight transfer

  • body control

Compression-adjustable shocks (rare outside high-end models) affect:

  • initial bump absorption

  • platform stability

  • harshness

Dežru adjusters always maintain:

  • predictable clicks

  • effective range

  • balanced changes

No “all the way hard” gimmicks.

Symptoms of Incorrect Damping

Too Little Rebound:

  • Car floats

  • Multiple oscillations

  • Lazy steering

  • Weight feels “delayed”

Too Much Rebound:

  • Harsh over cracks

  • Tire loses contact

  • Skipping over bumps

  • Rear instability on corner exit

Too Little Compression:

  • Bottoming out

  • Excess brake dive

  • Excess squat

Too Much Compression:

  • Harsh impacts

  • Harsh initial ride

  • Reduced grip on bumpy roads

Proper damping = predictable, stable, confidence-inspiring behavior.

Summary: What Is Damping?

✔ Compression = resistance during upward wheel movement

✔ Rebound = resistance during downward wheel movement

✔ Low-speed damping controls body movement

✔ High-speed damping controls bumps and impacts

✔ Linear pistons = smooth, predictable, daily-friendly

✔ Digressive pistons = sharp, responsive, track-ready

✔ Dežru's fixed-length design ensures valving operates in the ideal stroke range

✔ Damping is the #1 factor that determines how the car feels on the road

This is the most important concept in understanding suspension behavior.

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