Autocross Suspension Setups: Tuning for Quick Transitions
Autocross demands a unique approach to suspension tuning that focuses on agility, quick transitions, and maximum grip at low to medium speeds. Unlike high-speed track racing, autocross is typically a tight, technical sport with constant changes in direction, so every part of your suspension setup must be dialed in for precision and responsiveness. For Subaru enthusiasts, this means understanding how to adjust and select suspension components that will help them navigate a course with confidence and speed.
In this post, we’ll discuss how to set up your Subaru for optimal performance in autocross. We’ll cover suspension tips and mods for different SCCA autocross classes, including Street, Street Touring (ST), and Extreme Street (XS).
Key Factors in an Autocross Suspension Setup
Autocross setups are all about optimizing handling through quick weight transfer, precise cornering, and maximizing the tire contact patch. Here are the essential elements that define an effective autocross suspension:
1. Body Roll Control
Quick transitions require minimizing body roll to keep the car stable during sharp turns. This is often achieved with stiffer sway bars, firmer springs, and dampers that provide responsive handling without compromising traction.
2. Optimized Alignment
Alignment settings like camber, caster, and toe directly impact cornering grip and tire wear. Fine-tuning these settings lets you take advantage of the whole tire surface during rapid turns.
3. Quick Response
In autocross, responsiveness is critical. Modifications to bushings, control arms, and steering components can help create a more direct connection between the driver and the road, which is essential for managing tight corners and quick direction changes.
Autocross Suspension Modifications by SCCA Class
Street Class (SCCA) - Light Modifications with a Focus on Responsiveness
The Street Class allows minimal suspension modifications, making it a great place to start if you’re new to autocross. With strict limits, the focus is on making small adjustments that improve response without altering the core suspension system.
• Sway Bars: One of the best upgrades in Street Class is a thicker rear sway bar, which helps reduce understeer—a common challenge with Subarus in stock form. An upgraded sway bar will help keep the car level during cornering, giving it more grip and stability.
• Performance Alignment: Street Class rules allow for basic alignment tweaks. A bit of negative camber, especially in the front, improves cornering grip. Many Street drivers aim for -1.5 to -2.0 degrees of front camber and zero toe in the rear for stability.
• Performance Tires: While not a suspension component, sticky 200-treadwear tires are essential for competitive autocross in the Street Class. These tires dramatically improve grip and enhance every other upgrade you make.
Street Touring (ST) - Moderate Suspension Upgrades for Tunability and Grip
In Street Touring, more suspension modifications are allowed, giving you flexibility to dial in a serious autocross setup. This class balances performance with streetability, making it ideal for enthusiasts who drive their Subarus daily but still want competitive results on autocross courses.
• Coilovers: Coilovers allow you to adjust ride height and damping, which is ideal for customizing your Subaru’s balance and stability. Most autocross drivers in ST prefer single- or double-adjustable coilovers to optimize handling while keeping the setup manageable for street driving.
• Adjustable Camber Plates: Camber plates allow for greater negative camber adjustments, which helps increase cornering grip by maximizing the tire contact patch. For autocross, -2.5 to -3.0 degrees of camber in the front is common, while -1.5 to -2.0 degrees is typical in the rear for improved rear stability.
• Polyurethane Bushings: Replacing stock rubber bushings with polyurethane bushings reduces compliance, creating a more direct and responsive suspension feel. Bushings for control arms and sway bars are particularly effective, reducing unwanted movement during quick transitions.
• Upgraded Sway Bars (Front and Rear): A balanced sway bar setup in both front and rear improves rotation and allows for better tuning. Many Subaru owners in Street Touring run a thicker rear sway bar to dial out understeer, creating a more neutral handling balance.
Extreme Street (XS) - Aggressive Upgrades for Maximum Performance
Extreme Street allows for significant modifications, giving you freedom to build a nearly track-ready autocross machine while still being street-legal. For Subaru drivers in XS, tuning a suspension that maximizes grip and manages the car’s weight transfer at high cornering speeds is essential.
• Advanced Coilover Systems: High-quality, multi-way adjustable coilovers with separate adjustments for compression and rebound are common in XS. These allow you to fine-tune your Subaru’s handling to suit different autocross course layouts and surface conditions. Popular settings include stiffer rear damping to help rotate the car in tight turns.
• Adjustable Control Arms: Adjustable control arms allow for more aggressive alignment settings beyond what’s possible with camber plates alone. This gives you complete control over camber and caster, allowing for a setup that’s extremely dialed-in for handling sharp corners and quick direction changes.
• Solid or Spherical Bushings: In Extreme Street, many opt for solid or spherical bushings, which provide the most direct suspension feel. These bushings eliminate nearly all unwanted movement in the suspension, allowing for precise control at high speeds.
• Corner Balancing: For the most competitive XS setups, corner balancing ensures that the car’s weight is evenly distributed across all four wheels. This significantly improves stability and handling, especially during rapid transitions. A well-balanced car will remain neutral, helping it stay predictable and responsive.
Tuning Tips for Quick Transitions in Autocross
• Run a Stiffer Setup in the Rear: Subaru’s AWD system often results in understeer, which can be a disadvantage in autocross. To counteract this, consider using stiffer suspension settings in the rear to help the car rotate more easily through tight turns.
• Set the Ride Height for Low Center of Gravity: For optimal balance between grip and stability, set your Subaru’s ride height as low as possible without sacrificing suspension travel. A lower center of gravity reduces body roll and helps with quick changes in direction.
• Dial-In Dampers for Responsiveness: Autocross requires a suspension that can react instantly to driver input. Fine-tuning your damper settings can help. In general, softer rebound helps the car settle quickly after transitions, while firmer compression settings provide immediate response in corners.
• Optimize Tire Pressures: Tire pressures play a huge role in autocross performance. Higher pressures provide faster response and better turn-in, while lower pressures give a larger contact patch and increased grip. Adjust pressures based on the day’s conditions, track layout, and your car’s specific setup.
Conclusion
Whether you’re in Street, Street Touring, or Extreme Street, a well-tuned suspension is essential for navigating the sharp turns and tight course layouts typical in autocross. By focusing on quick transitions and balance, you can set up your Subaru to take on the competition with confidence.
Autocross is one of the best ways to test your car’s handling capabilities, and with the right suspension setup, your Subaru will be ready to tackle every cone and corner.