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FLEXIBLE PARTS
FUNCTIONS & BENEFITS

The engineering and testing behind flexible parts.

The Birth of Flexible Parts

Flexible Parts are STI’s signature body‑reinforcement parts, precisely engineered to unlock the full potential of SUBARU vehicles.

What kind of thinking lies behind their development, and what philosophy led to the creation of these uniquely engineered parts?

FLEXIBLE TOWER BAR
FLEXIBLE V BAR (For SUBARU BRZ)

FLEXIBLE DRAW STIFFENER FRONT

FLEXIBLE DRAW STIFFENER REAR

In the world of automotive development, it is widely accepted that greater body rigidity improves performance, while insufficient rigidity degrades it. STI has long shared this belief, continually asking ourselves which areas should be reinforced to increase rigidity.However, reinforcing one section can inevitably introduce negative effects in another. Recognizing this trade-off, we made the bold decision to step away from the conventional mindset of pursuing rigidity alone.Instead, we embraced the concept of “flexibility” — seemingly the opposite of rigidity.

By appropriately controlling body rigidity based on this concept, we created Flexible Parts that further refine and enhance the inherent performance of SUBARU vehicles.

Proven on the Track

STI has continually refined and advanced Flexible Parts conceived from this idea, drawing on expertise and feedback gained in motorsports.Germany’s Nürburgring is among the most demanding circuits in the world. Stretching 20.832 kilometers, with an elevation difference of 300 meters from its lowest to highest point and more than 150 challenging corners, it is a brutal test of both vehicle and driver. Its undulating, low‑grip surface and numerous blind corners incorporate elements of public roads, earning it a reputation as one of the toughest courses imaginable.

STI has long taken on the grueling Nürburgring 24-Hour race with SUBARU vehicles equipped with Flexible Parts.

By enhancing vehicle response and improving stability on both straights and through corners, these parts help the vehicle maintain composure even under the Nürburgring’s notoriously unpredictable weather—confidence‑inspiring performance that allows STI’s four drivers to focus fully on each lap, hour after hour.

The data acquired from these motorsports trials—such as adjustments to mounting positions and mechanisms—has been fed back directly into the development of Flexible Parts for use on public roads. One example is the FLEXIBLE DRAW STIFFENER REAR: its preload was refined based on the outcomes of repeated trials conducted on the Nürburgring race car under demanding conditions.

What Flexible Parts Deliver

Flexible Parts enhance vehicle response, enabling steering that feels natural, precise, and intuitive.

Flexible Parts deliver their benefits even from low speeds.With the vehicle responding exactly as the driver intends, unnecessary steering corrections are reduced, enabling a more relaxed and confident driving experience. As a result,the driver can calmly recognize the vehicle’s movements as well as the positions of surrounding vehicles and pedestrians.

Furthermore, by stabilizing the vehicle during driving,Flexible Parts help reduce unwanted shaking and lessen the risk of motion sickness,allowing not only the driver but all passengers to enjoy a more comfortable ride.

Experimental Comparison

Observable differences in vehicle attitude can be seen between vehicles equipped with and without Flexible Parts.
With Flexible Parts, there is less range of variation (see the following table), making it easier to drive the intended line and follow the course exactly as intended.

With FLEXIBLE PARTS

Without FLEXIBLE PARTS

Illustration of Vehicle Movement

Verification of Flexible Parts Effectiveness Using a Steering Robot

Differences can be seen in the variation of vehicle attitude across multiple runs.

With FLEXIBLE PARTS

Without FLEXIBLE PARTS

* For illustration purposes only.

Flexible Parts in Your Everyday Driving

How is performance on winding roads?

On roads where oncoming traffic emerges through a series of blind curves, drivers are required to make more delicate steering adjustments, which can quickly lead to fatigue. With Flexible Parts installed, the vehicle responds exactly as intended, reducing unnecessary steering effort and helping the driver maintain precise control with less strain.

What are the benefits during long highway drives?

Have you ever felt uneasy or fatigued on the highway because the vehicle was difficult to keep straight or tended to wander during lane changes?
With Flexible Parts installed, the tires grip the road surface more firmly, helping the vehicle maintain straight‑line stability and reducing sway when changing lanes. These improvements enhance peace of mind and reduce fatigue, making long‑distance highway driving more comfortable and enjoyable.

How about on rough roads, mountain roads, or in snowy conditions?

On unpaved mountain roads or slippery surfaces covered with snow, drivers often make repeated fine steering corrections unconsciously in response to changes in vehicle behavior, which leads to accumulated fatigue. With Flexible Parts installed, vehicle stability is improved, reducing the need for such fine steering inputs so that the driver can enjoy safer, more comfortable driving with less fatigue.

The Evolution of Flexible Parts

Control your car exactly as you intend, and enjoy a more comfortable and engaging driving experience.Flexible Parts will continue to evolve along with their expanding lineup.

Each Flexible Part is engineered for its respective vehicle model and is available across a wide range of SUBARU vehicles.For details, please contact your local SUBARU dealership or an authorized SUBARU distributor.

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