Clutch Masters FX350 vs FX400 for Subaru WRX and STI: Which One Is Right for Your Build

Clutch Masters is one of the most respected clutch brands in performance driving and one that WRX and STI owners frequently ask about when they outgrow the stock clutch. The FX350 and FX400 serve different power levels and driving styles — the decision between them is not just about which is stronger but about which fits the build. This guide covers what each clutch delivers and which one is right for your Subaru WRX or Subaru STI.

What Is Clutch Masters

Clutch Masters is a US-based clutch manufacturer that engineers clutch systems for high-performance street and track applications. What sets their products apart is the focus on clutch feel and drivability alongside torque capacity. Most performance clutch manufacturers optimize for maximum holding power at the expense of daily drivability. Clutch Masters engineers both — their clutches hold the power the build demands while keeping the pedal feel predictable and the engagement manageable for street use.

That balance is why the FX350 and FX400 are popular with WRX and STI owners who want a meaningful performance upgrade without committing to the aggressive engagement of a full ceramic or twin-disc setup.

What the FX350 Is Built For

The FX350 uses an organic full-face disc with an improved pressure plate that delivers higher clamping force than stock while maintaining street-friendly engagement characteristics. The pedal feel is heavier than stock but not dramatically so. Engagement is progressive rather than aggressive. For a daily-driven WRX that sees occasional performance driving, the FX350 delivers meaningful improvement without changing how the car feels to drive every day.

The FX350 is available for the WRX in two platform-specific versions. The Clutch Masters FX350 for 2015-2018 WRX covers the early FA20 platform. The Clutch Masters FX350 for 2018-2023 WRX covers the late FA20 and FA24 platform. Same clutch specification, different fitment for the early and late WRX generations. Confirm the model year before ordering.

What the FX400 Is Built For

The FX400 steps up to a puck disc design with higher clamping force and more aggressive engagement. Puck discs grab harder and release more quickly than organic full-face discs. The engagement is noticeable — the FX400 requires more deliberate clutch technique than the FX350, particularly at low speeds and in stop-and-go traffic. For track use and aggressive street driving, that engagement precision is exactly what the build needs. For a pure daily driver, it is more than most owners want.

The FX400 comes in platform-specific configurations. The Clutch Masters FX400 6-Puck for WRX is built for the FA20 and FA24 WRX platform. The Clutch Masters FX400 8-Puck for STI steps up to an 8-puck disc for the EJ257 STI platform. The additional pucks give the STI version more torque capacity to handle the power and engagement loads the EJ257 produces at performance power levels.

FX350 vs FX400: Which One Fits Your Build

The decision comes down to power level and how the car is used.

The FX350 is the right call for street-driven WRX builds with moderate power increases. If the build is in the stock to 350whp range and the car sees regular daily driving, the FX350 delivers improved clutch performance without changing the daily drivability. Owners who want a noticeable upgrade from stock without adjusting their driving technique will be well served by the FX350.

The FX400 is the right call for higher-power WRX and STI builds pushing 350whp and above, track use, and aggressive street driving where puck disc engagement suits the driving style. STI owners building toward serious power levels need the 8-puck torque capacity of the FX400 STI version — the EJ257 at performance power levels demands more from the clutch than an organic disc can reliably handle. Our clutch upgrades guide for WRX and STI covers how clutch stages work across the full range of performance options. Browse clutch kits for WRX and STI to compare everything available for the platform.

Completing the Clutch System

A clutch upgrade performs best when the full hydraulic and mechanical system supports it. Clutch Masters makes a complete range of supporting products for the WRX and STI that pair directly with the FX350 and FX400.

The Clutch Masters steel flywheel for STI is the right companion for the FX400 STI. A matched flywheel ensures the clutch system is properly balanced and performs as designed. Running a performance clutch disc against a worn or mismatched flywheel undermines the upgrade.

The Clutch Masters master cylinder for WRX and STI improves pedal feel and response. The stock master cylinder can become a weak point on higher-performance clutch setups where consistent hydraulic pressure matters. The Clutch Masters stainless clutch line for WRX and STI replaces the factory rubber clutch line with a stainless braided unit that reduces line flex and delivers more consistent clutch pedal feel under hard driving conditions.

What to Pair With a Clutch Upgrade

A performance clutch puts more load through the drivetrain on every engagement. Keeping the rest of the drivetrain stable under that load protects the clutch and the components around it. Solid transmission mounts for WRX and STI reduce drivetrain movement under the increased torque the new clutch delivers. Upgraded engine mounts for WRX and STI keep the drivetrain stable as clutch engagement becomes more aggressive at higher power levels.

Find the Right Clutch Masters Kit for Your WRX or STI

The FX350 is the balanced street performance choice for WRX owners who want meaningful improvement without changing daily drivability. The FX400 is the higher-power, more aggressive option for builds that demand more torque capacity and track-ready engagement. Both are purpose-built for the WRX and STI platform and backed by Clutch Masters engineering.

Browse the full range of clutch kits for WRX and STI to compare all available options, or explore the WRX performance upgrades hub to see how the clutch upgrade fits into the complete build picture.