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Springs

Spring Page

Configure corner springs and optional heave springs for each axle. Springs are the primary load-bearing element of the suspension and determine ride height, ride frequency, and weight transfer characteristics.

Each corner spring is an independent library component that can be saved, loaded, and shared separately.

Spring Types

Two spring types are available for corner springs. The type is determined by the actuation configuration in Kinematics.

Linear Spring

The default spring type. Operates in the linear (translational) domain, producing a force proportional to displacement.

Parameter Description Unit
Spring Rate Stiffness of the spring — constant value or 1D map (Distance vs Force) N/m
Preload Initial compression distance applied to the spring at rest m

The Spring Rate supports two data type modes:

  • Value — a single constant spring rate
  • 1D Map — a lookup table of displacement (m) vs force (N) for progressive or degressive springs

Torsion Bar

A torsion bar operates in the angular (rotational) domain, producing a torque proportional to rocker angle. Torsion bars are only available when the actuation type is set to push/pull rod with rocker in Kinematics. When actuation is set to direct-acting, the torsion bar option is disabled.

Parameter Description Unit
Torsion Stiffness Rotational stiffness — constant value or 1D map (Angle vs Torque) Nm/rad
Preload Angle Initial angular preload applied to the torsion bar rad

The Torsion Stiffness supports two data type modes:

  • Value — a single constant torsional stiffness
  • 1D Map — a lookup table of angle (rad) vs torque (Nm)

When to Use Torsion Bars

Torsion bars are common in Formula-style cars with rocker-actuated suspension. If your suspension is direct-acting (e.g., most production cars, GT cars), use linear springs.

Motion Ratios and Effective Rates

Spring parameters are entered at the component level (i.e., the physical spring itself). The motion ratio from Kinematics converts between component-level values and wheel-level values.

Linear Spring Motion Ratio

The spring motion ratio is the ratio between how much the spring moves relative to how far the wheel moves:

Motion Ratio = Spring Travel / Wheel Travel

It is a unitless value, typically less than 1. A higher motion ratio means the spring moves more for a given amount of wheel travel, making the suspension effectively stiffer. The effective wheel rate is:

Wheel Rate = Spring Rate x Motion Ratio²

Torsion Bar Motion Ratio

For torsion bars, the motion ratio is the ratio between the rocker angle and the wheel travel:

Motion Ratio = Rocker Angle (rad) / Wheel Travel (m)

This has units of rad/m. A higher motion ratio means the torsion bar twists more for a given amount of wheel travel, making the suspension effectively stiffer. The effective wheel rate is:

Wheel Rate = Torsion Stiffness (Nm/rad) x Motion Ratio² (rad/m)²

Motion ratios are read-only

Motion ratios are not entered on the Springs page — they are calculated from the suspension geometry defined in Kinematics. The Suspension Metrics panel shows the current motion ratios and resulting wheel rates.

Heave Springs

Heave springs are optional and toggled independently per axle. When enabled, a heave spring acts on the average wheel displacement of the axle, providing additional vertical stiffness without affecting roll stiffness.

Heave springs are always linear springs:

Parameter Description Unit
Spring Rate Heave spring stiffness — constant value or 1D map N/m
Preload Initial compression distance m

Heave Springs

Heave springs allow you to decouple ride stiffness from roll stiffness. A softer corner spring with a heave spring can give the same ride rate but lower roll stiffness than a stiff corner spring alone.

Validation Warnings

Linear Spring

Condition Warning
Preload distance > 10 mm High preload
Preload distance > 20 mm Extremely high preload
Preload distance < 0 Negative preload
Linearized spring rate < 10 N/mm Low spring rate
Linearized spring rate > 600 N/mm High spring rate

Torsion Bar

Condition Warning
Preload angle > 5° High preload angle
Preload angle > 10° Extremely high preload angle
Preload angle < 0 Negative preload angle
Linearized torsion stiffness < 1,000 Nm/rad Low torsion stiffness
Linearized torsion stiffness > 100,000 Nm/rad High torsion stiffness

Heave Spring

Condition Warning
Heave spring rate < 100 N/mm Very soft heave spring
Heave spring rate > 5,000 N/mm Very stiff heave spring