Mugen SI Suspension Parts: Complete Guide to Upgrading Your Civic Si

Upgrading the suspension on your Honda Civic Si can completely transform the driving experience, and Mugen suspension parts have long been a top choice for enthusiasts who want OEM-quality performance gains. Mugen, as Honda’s official tuning partner, designs components that complement the Si’s chassis without sacrificing daily drivability. Whether you own an 8th-gen, 9th-gen, or 10th-gen Civic Si, this guide covers the most popular Mugen suspension parts, what they do, and how to choose the right ones for your goals.

Mugen Sports Suspension System (Coilovers)

Mugen offers a complete coilover system for several Civic Si generations. Known as the Mugen Sports Suspension, these dampers and springs are engineered as a matched set to lower the car slightly while improving damping control.

Benefits of Mugen Coilovers

• Reduced body roll – Stiffer spring rates keep the car flatter through corners.
• Improved damping – Nitrogen-charged shocks respond faster to road irregularities.
• Height adjustability – On some models, you can fine-tune ride height by a small amount.
• Durability – Internals are built to handle track use while remaining compliant on the street.

Compatibility Notes

The 8th-gen (2006–2011) and 9th-gen (2012–2015) Civic Si share similar suspension architecture, but part numbers differ. The 10th-gen (2017–2020) Si uses a different strut design. Always verify your chassis code (FA5, FG2, FG4, FC1) before purchasing.

Mugen Sway Bars

Sway bars (or anti-roll bars) reduce lean without affecting spring travel. Mugen sway bars are hollow, lightweight, and tuned to work with the car’s factory geometry.

Front vs Rear Sway Bar

• Front sway bar – Increases turn-in response but can induce understeer if too stiff.
• Rear sway bar – Promotes rotation and neutral handling. Most Si owners upgrade the rear bar first.

Mugen typically offers a 22mm rear sway bar for the Si. This part is a direct bolt-on and works with stock end links. Installation takes about an hour with basic tools.

Mugen Strut Tower Bars

Strut braces tie the suspension towers together, stiffening the chassis under cornering loads. Mugen makes front and rear strut bars for the Civic Si.

• Front strut bar – Reduces flex in the upper shock mounts, improving steering precision.
• Rear strut bar – Stiffens the rear chassis, helping the rear suspension follow the front more predictably.

Both are aluminum and come in Mugen’s signature red anodized finish. They install with simple drilling (if your Si doesn’t have pre-existing mounting points) or bolt-in on later models.

Mugen Lower Control Arms and Bushings

For serious handling upgrades, Mugen offers reinforced lower control arms with stiffer bushings. These reduce deflection under braking and cornering.

• Pressed steel construction – Lighter than stock but stronger.
• Urethane bushings – Provide more feedback without being harsh.
• Geometry correction – Some arms adjust camber to regain alignment after lowering.

Note: Replacing control arms requires an alignment afterward. Budget around $150–200 for a proper alignment.

Mugen Springs (Only)

If you want a moderate drop without replacing the dampers, Mugen sells lowering springs tuned specifically for the Civic Si’s factory shocks.

• Drop – Typically 15–20mm lower than stock.
• Spring rate – About 15% stiffer than OEM, reducing body roll while maintaining comfort.
• Compatibility – Works with factory top hats and bump stops.

These springs are a good middle ground for daily drivers who want a sportier look and feel without going full coilover.

Choosing the Right Mugen Suspension Part for Your Civil Si

For Daily Driving and Street Manners

Start with a rear sway bar and front strut bar. These parts add noticeable handling improvement without making the ride harsh. They cost less than $500 total and install easily.

For Autocross or Track Days

Invest in the full Mugen Sports Suspension coilover kit. The adjustability lets you dial in damping for different surfaces. Pair it with Mugen’s sway bars to fine-tune balance.

For a Mild Lowering Job

Mugen lowering springs are the no-fuss option. They work with your existing shocks (if they are in good condition) and give a subtle, OEM+ stance. Be aware that after 30–50k miles, factory dampers may feel underdamped with stiffer springs.

Installation Considerations

• Tools needed – Basic socket set, spring compressor (for springs/coilovers), torque wrench, pry bar.
• Time – Springs: 2–3 hours per end. Coilovers: 4–6 hours total. Sway bars: 1–2 hours.
• Helpful extras – Penetrating oil, jack stands, alignment equipment.

If you are not comfortable working on suspension, have a professional shop do the install. A poor installation can lead to noise, premature wear, or unsafe handling.

Final Recommendation

For most Civic Si owners, the best starting point is the Mugen rear sway bar and front strut bar. These two parts deliver the most noticeable improvement in handling for the least money and effort. If you want to go further, add Mugen lowering springs for a mild drop, or jump straight to the Mugen Sports Suspension coilover kit if you plan to track the car. Always buy from authorized dealers to ensure authenticity—counterfeit Mugen parts exist and may compromise safety.

By choosing Mugen suspension parts, you get engineered components that work harmoniously with your Si’s chassis, backed by Mugen’s decades of Honda tuning expertise. Whether you’re carving back roads or attacking cones at an autocross, these parts will help your Civic Si reach its handling potential.