Suspension Secrets Adjustable Rear Traction Arms / Links - BMW F20 M135i/M140i

Suspension Secrets Adjustable Rear Traction Arms / Links – BMW F20 M135i / M140i

Improve acceleration, rear axle response and straight-line stability with Suspension Secrets Adjustable Rear Traction Arms for the BMW F20 M135i and M140i.

The factory BMW rear traction arms use compliant rubber bushes which can flex under hard acceleration. This movement can allow the rear wheel geometry to change dynamically, including unwanted changes to rear toe as torque is transferred through the suspension.

Suspension Secrets Adjustable Rear Traction Arms replace this compliant arrangement with solidly mounted, adjustable arms designed to keep the rear axle more accurately controlled under load.

The result is a more immediate response to throttle inputs, improved traction and a stronger sense of connection between the driver and rear axle.

Why Upgrade the Rear Traction Arms?

Reducing compliance in the rear suspension becomes increasingly important as power, tyre grip and acceleration forces increase.

Potential benefits include:

• Improved acceleration
• Increased straight-line stability
• More responsive rear axle behaviour
• Reduced unwanted toe change
• Improved throttle response through the chassis
• Higher corner-exit speeds
• Greater rear geometry control
• Particularly beneficial for tuned cars

Key Features

• Designed for BMW F20 M135i and M140i
• Fully adjustable rear traction arms
• Solidly mounted design
• Replaces rubber-bushed factory arms
• Helps reduce unwanted toe flex
• Improves rear axle response under acceleration
• Allows fine adjustment of suspension geometry
• Adjustable using a 17mm spanner
• Billet aircraft-grade 6082 T6 aluminium construction
• Corrosion-resistant stainless steel componentry
• Motorsport-spec Fluro bearings
• Designed and manufactured in the UK

The Problem With the Factory Traction Arms

The standard rear traction arms use rubber bushes to provide refinement and isolate road vibration.

While this works well for everyday comfort, the bushes can deform when subjected to high acceleration loads.

This can allow the rear hub to move relative to its intended position and cause dynamic geometry changes.

Reduced Toe Change Under Acceleration

One of the main benefits of replacing the compliant factory arms is improved rear toe control.

When the standard bushes flex under throttle, the rear toe angle can change.

This can affect:

• Straight-line stability
• Traction
• Rear axle confidence
• Corner-exit behaviour

The solidly mounted Suspension Secrets arms reduce this unwanted movement and help maintain more consistent geometry.

Improved Acceleration

Reducing rubber bush deflection creates a more direct path between the rear tyres and chassis.

This can make the car feel more immediate when the throttle is applied, particularly on higher-powered cars.

Potential improvements include:

• Quicker rear axle response
• Greater sense of connection
• More consistent traction
• Reduced feeling of suspension delay

More Responsive Rear Axle

Factory rubber bushes compress before the suspension reaches its loaded position.

Reducing this compliance means throttle inputs can be felt more directly through the chassis.

This can make it easier for the driver to understand how the rear tyres are responding to power.

Increased Straight-Line Stability

Keeping rear suspension geometry more consistent during acceleration can help the car remain more settled when applying significant power.

This is particularly valuable for:

• Tuned M135i and M140i models
• High-torque builds
• Drag-focused cars
• Performance road cars

Improved Corner-Exit Performance

The rear suspension experiences combined lateral and longitudinal forces when transitioning from cornering to acceleration.

Reducing unwanted suspension movement helps maintain a more predictable rear geometry during this transition.

This can allow power to be applied with greater confidence and contribute to higher corner-exit speeds.

Adjustable Rear Hub Control

The adjustable design allows the traction arm length to be fine-tuned to influence the position and rotation of the rear hub under acceleration.

This provides an additional level of suspension setup beyond what is possible with the fixed factory components.

Easy Adjustment

Suspension Secrets designed the arms to allow straightforward geometry changes.

Adjustment can be made using a 17mm spanner, making setup changes easier during:

• Professional geometry setup
• Track preparation
• Workshop adjustment
• Suspension development

Ideal for Tuned M135i & M140i Models

These arms become particularly relevant as engine output increases.

Additional torque places greater loads through the factory rubber suspension bushes, making unwanted deflection more noticeable.

They are especially suited to:

• Remapped cars
• Hybrid turbo builds
• High-power M135i models
• High-power M140i models
• Drag and roll-racing builds

Works With Other Rear Geometry Upgrades

Adjustable rear traction arms are most effective as part of a complete rear suspension setup.

They pair particularly well with:

• Adjustable rear toe arms
• Adjustable rear camber arms
• Adjustable rear upper third links
• Solid rear control arm bushes
• Coilovers
• Uprated anti-roll bars
• Performance geometry setups

Together, these upgrades provide significantly greater control over rear axle kinematics.

6082 T6 Aluminium Construction

Suspension Secrets uses billet aircraft-grade 6082 T6 aluminium for its suspension components.

This provides a combination of:

• High strength
• Low weight
• Durability
• Performance-focused construction

Corrosion-Resistant Stainless Steel

Stainless steel is used throughout the relevant hardware and adjustment components to improve durability in an exposed suspension environment.

Motorsport-Spec Fluro Bearings

The arms use motorsport-spec Fluro bearings for precise articulation and long-term performance under demanding loads.

These replace the compliance associated with conventional rubber bushings.

Road, Track & Drag Applications

Suspension Secrets Adjustable Rear Traction Arms are suitable for:

• Fast-road cars
• Clubsport builds
• Trackday cars
• Tuned road cars
• Drag builds
• High-power performance setups

NVH Considerations

Because these arms replace rubber-bushed factory components with solidly mounted, motorsport-oriented bearings, some increase in noise, vibration and harshness may be possible.

This is a performance-focused upgrade intended to prioritise rear axle response and geometry stability over factory levels of refinement.

Professional Installation Recommended

Professional installation is recommended.

After fitting, the vehicle should receive:

• Suspension inspection
• Rear geometry checks
• Rear toe adjustment
• Rear camber check
• Full wheel alignment
• Fastener checks

Geometry Setup Essential

A professional geometry setup should be carried out after installation.

The traction arm settings should be considered alongside:

• Rear toe
• Rear camber
• Ride height
• Tyre choice
• Intended road or track use
• Power level

Vehicle Fitment

BMW 1 Series F20

Compatible models:

• BMW M135i F20
• BMW M140i F20

What's Included?

Each kit includes:

• 1 pair Suspension Secrets Adjustable Rear Traction Arms / Links

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