Suspension Secrets Solid Rear Control Arm Bushes - BMW F20 M135i/M140i

Suspension Secrets Solid Rear Control Arm Bushes – BMW F20 M135i / M140i

Increase rear axle stability, consistency and cornering grip with Suspension Secrets Solid Rear Control Arm Bushes for the BMW F20 M135i and M140i.

The factory rear control arm bushes use compliant rubber, which can flex significantly during hard cornering. As the bushes deflect, the rear camber angle can change dynamically, reducing the consistency of the tyre contact patch and therefore the amount of grip available through the corner.

Because camber and toe are closely linked within the rear suspension geometry, this movement can also cause changes in rear toe, making the car feel nervous, unstable or as though the rear axle is “scrabbling” for grip.

The Suspension Secrets solid bush solution removes this unwanted compliance, helping keep rear camber and toe more consistent under load for a more predictable and confidence-inspiring rear end.

Why Upgrade the Rear Control Arm Bushes?

Reducing compliance in the rear suspension helps the geometry remain closer to the settings chosen during alignment.

Potential benefits include:

• Increased rear axle stability
• More consistent rear camber
• Reduced rear toe change
• Improved cornering grip
• More predictable handling
• Greater sense of connection to the rear axle
• Improved road and track performance
• Better stability during high-load cornering

Key Features

• Designed for BMW F20 M135i and M140i
• Solid rear control arm bush design
• Reduces unwanted suspension deflection
• Helps maintain rear camber under load
• Helps maintain rear toe under load
• Improved rear axle stability
• Increased cornering grip
• More precise handling
• Motorsport-grade Rodoball bearings
• Billet aircraft-grade 6082 T6 aluminium
• Corrosion-resistant 316 stainless steel components
• Designed and manufactured in the UK

The Problem With the Factory Bushes

The original rubber bushes are designed to provide refinement and isolate the chassis from road inputs.

That compliance is beneficial for comfort, but under harder driving it allows the rear control arms to move relative to the chassis.

This can cause the wheel alignment to change dynamically as cornering loads increase.

Dynamic Camber Change

As the rear control arm bush flexes, the rear camber angle can change.

This affects the way the tyre sits against the road surface and can reduce grip consistency through a corner.

Instead of maintaining the geometry chosen during alignment, the suspension can move away from those settings when the car is loaded heavily.

Dynamic Toe Change

Changes in rear camber can also influence rear toe.

Unwanted toe changes can make the rear axle feel:

• Nervous
• Inconsistent
• Less predictable
• Less stable at the limit

This is especially noticeable during fast direction changes and sustained high-load cornering.

More Stable Rear Geometry

The solid Suspension Secrets bushes are designed to minimise this movement.

By reducing bush deflection, rear camber and toe remain more consistent as the suspension is loaded.

This can help create:

• Greater rear-end stability
• More predictable grip
• Improved confidence
• More consistent cornering behaviour

Increased Cornering Grip

Keeping the rear wheel geometry more stable helps the tyre maintain a more consistent contact patch.

This can improve the way the rear axle generates grip through the corner, particularly when using:

• Performance road tyres
• Semi-slick tyres
• Uprated suspension
• Track-focused geometry

Improved Sense of Connection

Reducing rubber compliance creates a more direct connection between the rear suspension and chassis.

For the driver, this can result in a more immediate sense of what the rear axle is doing.

This is particularly valuable when driving close to the available grip limit.

More Precise Handling

Because the suspension geometry moves less under load, steering and chassis inputs can produce more repeatable results.

Potential improvements include:

• More predictable corner entry
• Greater mid-corner stability
• Improved rear-end confidence
• More consistent traction

Motorsport-Grade Rodoball Bearings

Suspension Secrets uses motorsport-grade Rodoball bearings within the bush assemblies.

These are selected to provide precise movement and durability in demanding suspension applications.

6082 T6 Aluminium Construction

Suspension Secrets components are manufactured using billet aircraft-grade 6082 T6 aluminium.

This provides a strong, lightweight structure suitable for high-load chassis applications.

316 Stainless Steel Components

Corrosion-resistant 316 stainless steel is used throughout relevant hardware and componentry.

This helps provide long-term durability in an exposed suspension environment.

Road & Track Use

These bushes are suitable for performance-focused road cars as well as track builds.

They are particularly well suited to:

• Fast-road M135i/M140i builds
• Clubsport cars
• Trackday vehicles
• Cars running performance geometry
• High-grip tyre setups

NVH Considerations

Because these bushes replace compliant factory rubber components with a solid, motorsport-oriented design, some increase in noise, vibration and harshness should be expected.

This is a more performance-focused upgrade intended for drivers who prioritise rear axle precision and geometry stability over factory levels of refinement.

Works Well With Other Suspension Upgrades

Solid rear control arm bushes work particularly well alongside:

• Adjustable rear camber arms
• Adjustable rear toe arms
• Adjustable rear traction arms
• Coilovers
• Uprated anti-roll bars
• Performance geometry setups
• Semi-slick tyres

Reducing unwanted bush movement allows these other components to work more consistently.

Professional Installation Recommended

Professional installation is recommended due to the need to remove and replace suspension bush components correctly.

After fitting, the vehicle should receive:

• Suspension inspection
• Fastener checks
• Wheel alignment
• Rear camber setup
• Rear toe setup

Geometry Setup Recommended

A professional geometry setup is strongly recommended after installation.

This ensures the improved suspension stability is matched with correctly configured:

• Rear camber
• Rear toe
• Ride height
• Overall chassis balance

Vehicle Fitment

BMW 1 Series F20

Compatible models:

• BMW M135i F20
• BMW M140i F20

What's Included?

Each kit includes:

• 1 pair Suspension Secrets Solid Rear Control Arm Bushes

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