This is How a Rear Sway Bar Will Unlock More Speed | Mk7 GTI

Grassroots Motorsports

8 Jul 202307:30

Summary

TLDRIn this video, the host demonstrates the installation of a larger rear sway bar on a Mark 7 Volkswagen GTI, explaining its benefits for track performance. The host uses a Miata antenna as a model to explain how sway bars function, reducing body roll and improving suspension dynamics. By increasing rear roll stiffness, the GTI can achieve a more neutral or oversteer-biased handling, reducing understeer. The video also covers related components like urethane bushings and adjustable end links. Overall, the modifications aim to improve the car's track performance without sacrificing daily driving comfort.

Takeaways

🔧 The video focuses on installing a larger rear sway bar on a Mark 7 Volkswagen GTI to improve track performance.
💡 A sway bar acts as a spring, resisting body roll by connecting both sides of a car's suspension.
🚗 The rear sway bar increases roll resistance, helping to reduce body roll and improve cornering on a track.
🔄 Installing a stiffer rear sway bar reduces dynamic negative camber loss, which keeps more tire traction during cornering.
🔧 The stiffer rear sway bar also helps correct the understeering nature of the GTI, shifting the handling balance towards oversteer for better cornering.
⚙️ The sway bar works by redistributing cornering loads between the front and rear of the car, which enhances grip and performance.
🔩 Adjustable end links ensure the sway bar remains neutral and doesn’t affect the car’s suspension when stationary.
🛠️ The use of urethane bushings reduces binding in the sway bar, making it more efficient and predictable in operation.
❗ Increasing spring rates by stiffening the sway bar reduces compliance, meaning the car will be less smooth over bumps.
🏁 The modification is aimed at improving track performance without compromising much on daily driving comfort.

Q & A

What is the purpose of installing a bigger rear sway bar on a car?
-A bigger rear sway bar increases rear roll stiffness, helping control body roll and shifting the car's handling balance from understeer towards oversteer, which can improve performance, especially in front-wheel-drive cars like the GTI.
How does a sway bar function in a car's suspension system?
-A sway bar acts as a spring between the two sides of the car's suspension. It allows for little resistance when both wheels move together but resists when one wheel moves independently, adding roll resistance and helping manage body roll during cornering.
Why is reducing body roll important for track performance?
-Reducing body roll helps minimize dynamic camber changes, especially on cars like the GTI. This ensures the tires maintain better contact with the track, improving grip and handling.
What is dynamic camber change and why is it undesirable?
-Dynamic camber change refers to the gain or loss of negative camber as the suspension moves through its range. It’s undesirable because it can reduce the contact patch of the tires with the road, reducing traction.
Why is increasing rear roll stiffness particularly useful for front-wheel-drive cars?
-Increasing rear roll stiffness can shift more of the cornering load to the rear of the car, reducing the load on the front, which helps mitigate understeer—a common issue in front-wheel-drive cars like the GTI.
What is the function of sway bar bushings and why are urethane bushings used in this project?
-Sway bar bushings allow the bar to rotate freely. Urethane bushings are used because they reduce binding and deflection compared to stock rubber bushings, ensuring more predictable and efficient performance from the sway bar.
What role do adjustable end links play in the sway bar setup?
-Adjustable end links connect the sway bar to the suspension and allow fine-tuning so the sway bar doesn’t press on the suspension at rest. This ensures the sway bar operates evenly without biasing one side.
What are the potential downsides of increasing spring rates with a stiffer sway bar?
-The downside of increasing spring rates is the reduction in suspension compliance, which can make the car less able to absorb bumps and changes in the road surface. However, in this case, the trade-off is expected to improve track performance.
How does a stiffer sway bar impact daily driving comfort?
-While a stiffer sway bar reduces suspension compliance, in this project, it is not expected to significantly affect daily driving comfort despite the increase in roll stiffness.
Why was a demonstration with a Miata antenna used in the video?
-The Miata antenna, acting as a spring in the demonstration, was used to visually explain how a sway bar functions. It shows how the sway bar resists twisting, illustrating the spring effect that helps control body roll in a car.

Outlines

00:00

🔧 Introduction to Rear Sway Bar Upgrade for the GTI

The video begins with a focus on upgrading the rear sway bar of a Mark 7 Volkswagen GTI, explaining how this modification can improve performance on the track. Although the primary focus is on front-wheel-drive cars like the GTI, the advice applies to most vehicles. The presenter starts with an illustration using a Miata antenna to explain how sway bars function, comparing them to springs that act rotationally. This demonstration leads to an explanation of the sway bar’s role in reducing body roll and increasing roll resistance, which can be fine-tuned separately from the main suspension spring rate.

05:00

🚗 Sway Bar Mechanics and Its Role in Handling

The next part discusses the sway bar's function as a spring that connects the left and right sides of the car’s suspension. When one wheel moves, the sway bar resists that movement, creating roll resistance that helps reduce body roll during cornering. This section goes deeper into the benefits of having a sway bar in the rear suspension, explaining how it can independently adjust roll resistance and improve the car’s handling, making it faster or more comfortable without compromising ride quality.

📏 Upgrading to a Bigger Rear Sway Bar for GTI Performance

The presenter shifts focus to the upgraded sway bar for the GTI, a front-wheel-drive car. The larger sway bar is expected to control body roll, reduce negative camber loss, and enhance traction in the front tires during cornering. The main reason for upgrading the rear sway bar is to reduce understeer and help the car handle more neutrally or even slightly oversteer. This is achieved by increasing the rear roll stiffness, which shifts some of the cornering load from the front to the rear, improving the car’s overall cornering ability.

🔩 The Importance of Free-Moving Sway Bars

The focus turns to the parts surrounding the sway bar, specifically the sway bar bushings. Ideally, these bushings should allow the sway bar to move freely without adding resistance, but stock rubber bushings often bind and are poorly lubricated. To fix this, the presenter plans to install urethane bushings from 034 Motorsport, which are greasable and stiffer, allowing the sway bar to move more predictably and without deflection. Adjustable end links will also be installed to ensure that the sway bar is not biased toward one side when the car is at rest, ensuring better handling.

⚖️ Downsides of Increasing Rear Roll Stiffness

Although increasing the rear roll stiffness offers many performance benefits, it comes with the downside of reduced compliance. Anytime spring rates are increased, the car becomes less able to absorb bumps and variations in the road, which can affect comfort. However, the presenter believes the trade-off will be worthwhile, as the sway bar upgrade should make the GTI faster on the track without significantly affecting its drivability in daily use.

🏁 Final Thoughts and Call to Action

The video wraps up with a summary of the anticipated benefits of the sway bar upgrade and a call to action for viewers. The presenter mentions that the next step is to install the upgraded parts and take the GTI to the racetrack. Finally, viewers are encouraged to like the video, subscribe for more content, and visit the Grassroots Motorsports website for additional resources, supported by CRC Industries.

Mindmap

Keywords

💡Sway Bar

A sway bar, also known as an anti-roll bar, is a part of a vehicle's suspension system designed to reduce body roll during cornering. In the video, the presenter explains how the sway bar acts like a spring, working rotationally to resist the car’s body roll. This component is a key tuning tool for controlling the balance of a car’s suspension, especially in performance cars like the GTI being worked on.

💡Roll Resistance

Roll resistance refers to the ability of a suspension system to resist the body of the car leaning or rolling during cornering. In the video, the sway bar is introduced as a tool to increase roll resistance, particularly beneficial for reducing body roll in the rear of the car. This is important in improving vehicle dynamics and cornering performance on the track.

💡Spring Rate

Spring rate is the measure of a spring's stiffness, or how much force is required to compress or extend it. The presenter discusses how changing spring rate can help with handling and comfort, particularly in balancing performance on track and comfort for daily driving. A sway bar affects roll resistance without directly altering the spring rate, allowing for more fine-tuned handling adjustments.

💡Dynamic Camber

Dynamic camber refers to changes in the angle of a vehicle’s wheels relative to the road as the suspension moves through its range of motion. In the video, the presenter emphasizes that reducing body roll with a stiffer rear sway bar will help maintain consistent negative camber, particularly important for the front wheels of the GTI, which helps preserve tire grip during cornering.

💡Understeer

Understeer occurs when the front wheels lose grip and the car continues to go straight despite the driver steering into a turn. The presenter highlights that the GTI, being a front-wheel-drive car, tends to understeer, and increasing rear roll stiffness with a bigger rear sway bar is aimed at mitigating this problem to create a more neutral or even oversteer-biased handling characteristic.

💡Oversteer

Oversteer is when the rear wheels lose grip, causing the rear of the car to swing outwards in a turn. The video discusses how increasing rear roll stiffness could help bias the GTI’s handling toward oversteer, which would aid in better turn-in and cornering, helping to reduce the inherent understeer of front-wheel-drive cars.

💡End Links

End links are the components that connect the sway bar to the vehicle’s suspension. The video mentions that adjustable end links are used in this project to ensure that the sway bar is not exerting unwanted force on the suspension when the car is at rest. Properly adjusted end links allow for balanced suspension and precise handling, especially important for track use.

💡Body Roll

Body roll is the tilting or leaning of a car's body towards the outside of a turn due to inertia. The presenter discusses how reducing body roll is crucial for maintaining consistent tire contact and improving cornering performance, particularly in the GTI, where minimizing body roll helps keep dynamic camber changes in check.

💡Compliance

Compliance refers to the suspension's ability to absorb bumps and irregularities in the road, allowing the tires to maintain contact with the surface. The video points out that increasing spring rates or roll stiffness, such as by adding a stiffer rear sway bar, reduces compliance. While this makes the car faster on smooth tracks, it may reduce comfort and handling precision on uneven surfaces.

💡Bushings

Bushings are the rubber or urethane components that cushion and allow movement between suspension parts. The video discusses replacing the stock rubber bushings with urethane ones for the rear sway bar, which are stiffer and greasable, allowing the bar to move freely without binding. This modification is important for keeping the sway bar's movement predictable and consistent during cornering.

Highlights

Introducing the Mark 7 Volkswagen GTI project and the plan to install a bigger rear sway bar for improved track performance.

Explanation of how changing the size of a sway bar can impact a car's performance, with a focus on front-wheel drive vehicles like the GTI.

Demonstration using a Miata antenna as a simple model to explain how sway bars function like a big spring, resisting rotational movement.

The role of sway bars in reducing body roll by increasing roll resistance, which is crucial for maintaining better tire contact during cornering.

Discussion on how sway bars can be used to tune suspension independently of the spring rate, offering more control over a car's handling characteristics.

Description of the basic design of a sway bar, highlighting its straight part and two levers, and how it interacts with the suspension system.

Installation of zero three four Motorsport rear sway bar on the GTI, emphasizing the bar’s design to fit the vehicle while maintaining its fundamental function.

Detailed explanation of how a stiffer rear sway bar helps in controlling body roll and reducing dynamic camber loss, particularly beneficial for the GTI’s front suspension.

The primary reason for installing a bigger rear sway bar: to increase rear roll stiffness, shifting the car's balance towards oversteer, which enhances turn-in and cornering stability.

Discussion on how altering roll stiffness at the rear of a front-wheel-drive car like the GTI can reduce understeer, leading to more neutral handling.

Importance of sway bar bushings and end links in ensuring the sway bar operates without resistance, binding, or unintended spring rate changes.

Advantages of using urethane bushings for the sway bar, which reduce deflection and enhance predictability in handling.

Introduction of adjustable end links, which allow for precise tuning of the sway bar's effect on the suspension, ensuring balanced performance.

Discussion of the trade-offs involved in increasing roll stiffness, such as reduced compliance and the impact on comfort versus performance.

Conclusion highlighting the expected benefits of the rear sway bar upgrade in terms of track performance and the minimal impact on daily driving comfort.