The Ultimate Guide to Focus ST Suspension Parts: Upgrades, Replacements, and Tuning Tips

The Ford Focus ST is a performance hatchback known for its sharp handling and engaging driving dynamics. Its suspension system plays a key role in delivering that experience, but as the car ages or as you seek more track-ready performance, upgrading or replacing suspension parts becomes a practical consideration. This guide covers the essential Focus ST suspension parts, their functions, upgrade options, and factors to keep in mind when building a suspension setup that matches your driving goals.

Understanding the Focus ST Factory Suspension

The stock suspension on the Focus ST was designed to balance daily comfort with spirited driving. It features MacPherson struts up front and a multilink rear setup, with relatively stiff springs and adaptive dampers on ST3 models. The factory ride height is moderate, and the roll control is good for a front-wheel-drive car. However, many owners find the stock suspension too soft for autocross or track days, or too harsh for rough roads. Upgrading specific components can address these trade-offs.

Key Components of the Focus ST Suspension

• Struts and Shocks – Front struts and rear shocks control compression and rebound. Upgrading to adjustable coilovers or performance shocks can improve damping characteristics.
• Springs – Lowering springs reduce the center of gravity and reduce body roll. Progress springs offer a balance of comfort and performance.
• Sway Bars – Also called anti-roll bars, these reduce body lean during cornering. A thicker rear sway bar can reduce understeer, a common issue in the Focus ST.
• Control Arms and Bushings – Upgraded lower control arms with stiffer bushings improve camber adjustment and reduce deflection.
• End Links – Connect sway bars to the suspension. Adjustable end links are recommended when lowering the car to prevent binding.
• Strut Tower Braces – Stiffen the chassis, improving steering response and reducing flex.
• Coilovers – Combined spring and damper units that offer ride height adjustability and often finer damping tuning.

Coilovers vs. Springs and Shocks: Which Setup is Right for You?

When upgrading suspension, the first major choice is between a full coilover set or a spring-and-shock combination. Each has its strengths depending on your use case.

Coilovers for Track and Autocross

Coilovers provide the most adjustability. Higher-end sets allow independent ride height adjustment and separate compression/rebound damping. For a Focus ST used predominantly for track days or competitive driving, coilovers are the go-to. Brands like KW, BC Racing, and Fortune Auto offer popular options. The ability to corner-weight the car and fine-tune damping makes a noticeable difference in lap times.

Lowering Springs + Performance Shocks for Street and Light Duty

If you drive the car daily and only occasionally push it on backroads, a quality set of lowering springs paired with performance shocks (like Koni Yellow or Bilstein B6) can be a more cost-effective and comfortable solution. This combination lowers the car about 1-1.5 inches, improves appearance, and reduces body roll without the harshness of a race-oriented coilover. Many street-focused owners find this setup strikes a good balance.

Choosing the Right Sway Bar Upgrade for the Focus ST

Sway bars are one of the most effective suspension upgrades for changing handling balance. The factory bars are thin and prioritize comfort. A thicker rear sway bar reduces understeer and lets the car rotate more easily. For the Focus ST, a common upgrade is a 25mm to 28mm rear bar while keeping the stock front bar or upgrading to a slightly thicker front bar (e.g., 27mm). Adjustable bars allow you to fine-tune oversteer bias.

Installation Considerations

Replacing sway bars is a straightforward DIY job for someone with basic tools, but pay attention to end links: if you lower the car, you’ll need adjustable end links to prevent preloading the sway bar. Many kits come with them, but always confirm.

Bushings and Control Arms: Sharpening Steering Response

Over time, rubber bushings in the front control arms and rear trailing arms wear out, leading to vague steering and sloppy handling. Upgrading to polyurethane or spherical bearings can drastically improve feedback. For daily driving, polyurethane is recommended as it reduces flex without making NVH unbearable. Spherical bearings are best for track-only cars due to increased noise.

Camber Adjustment

After lowering, you’ll likely need camber bolts or adjustable camber plates to bring alignment within spec. The Focus ST front suspension uses a strut design that does not have factory camber adjustment; aftermarket camber bolts (like from SPC) are an affordable fix. Rear camber is adjustable via the stock eccentric bolt, but aftermarket arms offer more range.

Brakes and Suspension: A Note on Combined Upgrades

While not strictly suspension, upgrading brakes is often done in tandem. If you plan on track days, consider upgrading pads, rotors, and brake fluid. For severe track use, a big brake kit (BBK) may be necessary, but for most street-plus driving, high-performance street pads and slotted rotors are sufficient.

Recommended Suspension Parts for Different Budgets

Budget-Friendly: Improve Handling Under $500

• Rear sway bar (upgrade to 25mm from Eibach or Steeda)
• Front camber bolts
• Polyurethane bushings for front LCA (if stock are worn)
• Good performance shocks like Koni Orange or Bilstein B8 if struts are worn

Mid-Range: Springs and Shocks Combo ($500 – $1,200)

• Lowering springs (e.g., H&R Sport, Eibach Pro-Kit)
• Performance struts/shocks (Koni Yellow, Bilstein B6)
• Adjustable end links
• Rear sway bar (if not already done)

High-End: Full Coilover Setup ($1,200 – $3,000+)

• BC Racing BR series (entry-level adjustable)
• KW V1 or V2 for street/track balance
• Fortune Auto 500 with Swift springs for better ride quality
• Optional: adjustable camber plates, spherical bearings

Installation and Maintenance Tips

• Always get a professional alignment after any suspension change.
• If installing coilovers, set ride height to manufacturer recommended baseline first.
• Check all bolts after 100 miles of driving to ensure they haven’t loosened.
• Re-grease polyurethane bushings periodically if they squeak.
• For street use, avoid excessively low ride heights that cause bump steer and scrapes.

Common Mistakes to Avoid

• Mixing mismatched springs and shocks – Always use shocks designed for the spring rate.
• Over-adjusting sway bar stiffness – A too-stiff rear bar can cause snap oversteer on wet roads.
• Ignoring alignment after lowering – Can cause premature tire wear and poor handling.
• Choosing coilovers solely for price – Cheap units often have poor damping and short life.

Practical Recommendation

For a realistic balance of performance and daily drivability, start with a rear sway bar upgrade and performance lowering springs with matched shocks. This gives you a significant handling improvement for under $1,000. If you plan to track the car regularly, invest in a quality set of coilovers from KW or BC Racing, and add adjustable end links and camber bolts. Always prioritize bushings and alignment to get the most out of your setup. Remember that suspension is a system – each component affects the others, so plan your upgrades as a cohesive package rather than buying random parts.