Eibach 06-11 & 12-15 Honda Civic Si Rear Anti-Roll Bar

Take your Civic’s handling to the next level with the Eibach 4031.312 Rear Anti-Roll Bar. Designed specifically for the 06-11 Civic Si (8th Gen) and 12-15 Civic Si (9th Gen), this upgrade tackles the factory understeer and gives your car sharper, more balanced cornering. Whether you’re carving backroads or pushing through an autocross course, this rear sway bar delivers the flat, confident handling every FWD driver craves.

Who?

You the driving enthusiast, weekend autocrosser, or track-day hero behind the wheel of a late-model (8th or 9th generation) Honda Civic Si.

What?

The Eibach Anti‑Roll Bar Kit (Rear Only), part number 4031.312, a solid, two‑way‑adjustable rear sway bar engineered to sharpen your car’s cornering prowess — available for both 8th Gen (06–11) and 9th Gen (12–15) Honda Civic Si (excluding hybrids)

Where?

Manufactured in the USA by Eibach, a brand renowned for motorsport-grade suspension, this bar integrates seamlessly into your Civic’s rear suspension whether paired with OEM springs or part of a more advanced coilover setup

When?

Install it when you want to reduce body roll, improve chassis stability, and boost grip. It’s especially impactful during mid‑corner transitions or spirited street driving basically now if you're craving sharper performance.

Why?

• Precision‑tuned for Balance & Control: The adjustable rear bar tames unwanted roll, delivering crisp, responsive behavior during cornering, braking, and accelerating
• Improved Vehicle Dynamics: Sharper handling, flatter turn‑in, and more predictable behavior under load, giving you confidence in every apex
• Versatile Compatibility: Works flawlessly with stock suspension or tuned setups. If you're not in a Civic Si trim, you may need the additional hardware kit 4031.312HKR
• Made in the USA & Backed: Built domestically, each bar undergoes vehicle-specific testing, and Eibach even backs it with a limited lifetime warranty
• Grip & Stability Boost: On FWD cars like the Civic, rear sway bars help reduce lift at the outside rear wheel during cornering. The result? A more neutral, balanced turn-in and quicker mid-corner transitions.

Behind the Mechanics: Rear-Only Sway Bar Upgrade on a FWD Car

Front-wheel-drive vehicles typically exhibit understeer, especially when the front tires struggle with both steering and propulsion loads. A stiffer rear anti-roll bar shifts some of that balance:

• Reduces Rear Compliance: During lateral loads, the stiffer rear bar resists body roll, keeping the chassis flatter and the rear tires more planted.
• Promotes Even Weight Distribution: Less weight shifts from the inside to the outside rear wheel, maintaining grip on both rear tires.
• Sharper Turn-In Response: With a more controlled rear end, the car responds more immediately at entry, reducing understeer.
• Tunable Balance: The two-way adjustability allows you to dial in exactly how much rear roll stiffness you prefer perfect for matching your driving style or tire setup.

Final Thoughts

The Eibach 4031.312 Rear Anti-Roll Bar is not just an upgrade it’s your billet solution for dialed-in balance and professional-grade handling on the street or track. Designed and tested for your chassis, it slots into your Civic Si (or compatible non-Si with the hardware kit) and transforms turn-in and mid-corner dynamics. Simple, effective, dealer-grade performance.