ACT ACTSB12-HDG6 Heavy Duty Race Sprung 6 Pad Clutch Kit 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Subaru WRX Impreza WRX EJ255 FA20 FA24

The ACTSB12-HDG6 is ACT's Heavy Duty Race Sprung 6 Pad Clutch Kit built for 2005-2025 Subaru WRX, Legacy GT, Forester XT, Outback XT, and Baja Turbo applications running the 2.5L Turbo H4 (EJ255), 2.0L Turbo H4 (FA20), or 2.4L Turbo H4 (FA24) engine. This complete kit upgrades the factory 230mm clutch system to a 240mm platform, delivering 574 ft-lbs of crank torque capacity (approximately 78% over OE) through ACT's proven Heavy Duty pressure plate paired with a 6-Pad Sprung ceramic race disc. The ACTSB12-HDG6 includes the ACT XACT Prolite chromoly flywheel, release bearing, and alignment tool so you have every component needed for a complete drivetrain overhaul in a single purchase.

What's Included

• ACT Heavy Duty Pressure Plate (part of SB12-HDG6 assembly) - upgraded clamp load with exclusive diaphragm design
• ACT 6-Pad Sprung Race Disc #6240518 - 240mm (9.4 in) ceramic cerametallic disc, spring-centered hub
• ACT XACT Prolite Chromoly Flywheel #600895 - 8.5 lbs, precision-balanced, chromoly steel
• Release Bearing #RB844
• Alignment Tool #AT90

Heavy Duty Pressure Plate

The ACTSB12-HDG6 is built around ACT's most popular Heavy Duty (HD) pressure plate, which uses an exclusive diaphragm design to increase clamp load above stock levels while simultaneously reducing deflection. Higher clamp load is what enables the 574 ft-lbs torque rating, and reduced deflection means the pressure plate maintains consistent engagement force lap after lap without fade. Every ACT diaphragm undergoes a four-stage heat-treating process for unparalleled durability under high-heat, high-RPM racing conditions. Precision cover stampings provide rigidity and dimensional consistency across the full service life of the clutch. Compared to the Xtreme pressure plate found in the ACTSB12-XTG6, the HD unit delivers a more manageable pedal feel, making this kit a realistic choice for drivers who see both track days and spirited street miles.

6-Pad Sprung Ceramic Race Disc

Part number 6240518 is ACT's 240mm (9.4 in) 6-Pad spring-centered ceramic race disc. The cerametallic friction material withstands the extreme heat generated during repeated hard launches and aggressive track driving far better than organic compounds. Six pads distributed around the face increase heat capacity compared to a 4-pad disc, and the larger 240mm diameter (up from the OEM 230mm) further extends the disc's thermal headroom. The spring-centered hub on this disc uses coil springs between the hub and disc plate to dampen torsional vibrations coming from the drivetrain. This is a meaningful distinction from a rigid-hub disc (see the ACTSB12-HDR6 in the comparison table below): the sprung hub absorbs shock loads, protecting the transmission input shaft and the rest of the driveline from the harshness that is inherent in a high-torque ceramic engagement. ACT spring retainers on this disc use wraparound spring windows and thicker retainer stampings to support the springs under load, reduce stress concentrations, and extend the life of the assembly. Engagement is firm and direct compared to a street disc, and clutch engagement speed is fast, which allows for quicker, more precise shifts at the limit.

Note: This race configuration is designed for motorsport and performance driving applications. It is not recommended as an everyday street clutch for drivers who primarily commute in heavy traffic.

ACT XACT Prolite Chromoly Flywheel

The XACT Prolite flywheel (part number 600895) is the piece that makes the SB12 series a true complete conversion kit. Machined from high-strength chromoly steel and weighing just 8.5 lbs, the Prolite flywheel is dramatically lighter than the heavy cast-iron OEM unit it replaces. Reduced rotational inertia means the engine revs rise and fall faster, translating directly into sharper throttle response, quicker downshift blips, and improved acceleration out of corners. The flywheel is precision-balanced as part of the complete assembly to minimize vibration across the RPM range. Because this kit upgrades the clutch diameter from 230mm to 240mm, the included ACT XACT Prolite flywheel is required; the 240mm disc is not compatible with an unmodified OEM flywheel or any prior 230mm aftermarket flywheel without machining. This is an important installation consideration and is covered further in the fitment notes below.

Vehicle Fitment

Fitment Notes: 240mm Conversion and 2018 WRX VIN Consideration

The ACTSB12-HDG6 is a 240mm conversion kit for all vehicles listed above. The factory Subaru WRX and related platforms shipped from the factory with a 230mm clutch. The ACT XACT Prolite flywheel (#600895) included in this kit is required for proper fitment and must be installed together with the disc and pressure plate. Do not attempt to use the 240mm disc with a stock flywheel or a flywheel designed for a 230mm clutch.

For 2018 Subaru WRX owners: Subaru introduced a running production change mid-year 2018. Vehicles built after VIN sequence J806877 received an OEM 240mm clutch from the factory. If your 2018 WRX has a VIN after J806877, your car already has the larger 240mm flywheel and clutch from the factory. The ACTSB12-HDG6 is still fully compatible with these VINs, and the included Prolite flywheel replaces the heavier OEM unit regardless of which 240mm variant came in your car from the factory.

Full Specifications

California Proposition 65 Warning

WARNING: This product can expose you to chemicals including nickel compounds and chromium (hexavalent compounds), which are known to the State of California to cause cancer, and carbon monoxide and lead, which are known to the State of California to cause birth defects or other reproductive harm. For more information, visit www.P65Warnings.ca.gov.

Warranty

This clutch kit is covered by a 12-month ACT limited warranty from Advanced Clutch Technology (ACT). This warranty covers defects in materials and workmanship under normal use and proper installation conditions. Warranty claims must be submitted directly to ACT with proof of purchase. Coverage under this warranty does not affect any rights you may have under the Magnuson-Moss Warranty Act (15 U.S.C. 2301 et seq.) or applicable state consumer protection laws. The Magnuson-Moss Warranty Act provides federal minimum standards for written warranties on consumer products and preserves your right to seek remedies under both the written warranty and implied warranty protections available under state law. Installation of this product by a qualified professional is strongly recommended and may be required for warranty claims. Warranty does not cover normal wear, improper installation, abuse, racing incidents, or damage resulting from use with incompatible components.

SB12 Series Comparison: Which Kit Is Right for Your Build?

ACT offers the SB12 series in multiple disc and pressure plate configurations. All SB12 kits share the same XACT Prolite flywheel and upgrade to the 240mm platform. The right choice depends on your power level, driving style, and how much engagement harshness you can tolerate.

About Advanced Clutch Technology (ACT)

Advanced Clutch Technology is an American clutch manufacturer headquartered in Lancaster, California (93535). Founded on the principle that enthusiast drivers deserve better than what the OEM supply chain offers, ACT engineers and manufactures every component in-house, from pressure plates to flywheels to release bearings. ACT's engineering team focuses on metallurgy, diaphragm geometry, and friction material science to produce clutch systems that outperform stock equivalents in torque capacity, heat resistance, and longevity. The company's products span a wide range of applications, from daily-driven street cars to dedicated competition vehicles in rally, time attack, and drag racing. ACT's manufacturing processes include multi-stage heat treatment of diaphragm springs, precision CNC machining of flywheel surfaces, and rigorous quality control at every production stage. For Subaru WRX owners in particular, ACT has developed a comprehensive lineup covering the full evolution of the WRX platform, from the EJ-series engines of the 2000s through the modern FA-series turbocharged flat-fours used in current production vehicles.

Frequently Asked Questions

Q: Which ACT SB12 disc is right for my power level?

A: The organic street disc in the ACTSB12-HDSS is rated for 449 ft-lbs and works well for lightly modified WRX builds in the 300-350 whp range that are primarily street driven. If you are running more power or spending meaningful time on track, a ceramic disc is the better choice. Both the ACTSB12-HDG4 and this kit share the same 574 ft-lbs rating; the 6-pad disc here handles more heat due to its greater friction surface area, making it the preferred choice for repeated hard launches or extended track sessions. If your build is at or above 500 whp, look at the ACTSB12-XTG6 with its 681 ft-lbs Xtreme pressure plate. If you are unsure, choose one level above what your current tune requires; clutch upgrades are labor-intensive, and the extra margin is worth it.

Q: What is the difference between a sprung hub disc and a rigid hub disc?

A: A sprung hub disc, like the one included here, uses coil springs between the hub flange and the friction disc plate to absorb torsional shock loads during engagement. This cushioning protects the transmission input shaft splines, gear teeth, and other driveline components from the sharp engagement impulses that are characteristic of ceramic clutches. A rigid hub disc has no springs; the hub and friction material are essentially one solid unit. Rigid hubs provide a slightly more direct mechanical connection with less rotational play, which is why some full-competition setups prefer them. However, rigid hub setups transmit all engagement shock directly into the transmission, which increases driveline wear over time. For most WRX track builds that also see street miles, the sprung hub in this kit is the correct choice. The ACTSB12-HDR6 uses the same pressure plate and 6-pad ceramic disc but with a rigid hub if you specifically need that configuration.

Q: Does the ACTSB12-HDG6 fit the Subaru WRX STI?

A: No. This kit is not compatible with any Subaru WRX STI model year. The STI uses a different transmission bellhousing, a larger stock clutch diameter, and a different input shaft. ACT produces separate clutch kits for the STI platform. If you own a WRX STI, search for ACT STI-specific part numbers based on your year. This kit is verified to fit the non-STI WRX (VA and VB chassis), the 2006 to 2014 Impreza WRX, and the Legacy GT, Outback XT, Forester XT, and Baja Turbo applications listed in the fitment table above.

Q: What does the 240mm clutch conversion mean, and do I need to do anything special?

A: Most turbocharged Subaru WRX and related models from 2005 through mid-2018 came from the factory with a 230mm clutch and flywheel. A 240mm conversion replaces both with a larger-diameter system, which increases the friction surface area of the disc. More surface area means more heat capacity and more potential torque capacity without increasing clamp load to extremes. This is a 240mm kit, which means you cannot mix its components with your OEM 230mm flywheel. The ACT XACT Prolite flywheel #600895 included in this kit is machined specifically for the 240mm disc and must be installed as part of the complete assembly. There is no additional machining required if you are installing all components together as a kit.

Q: How much lighter is the XACT Prolite flywheel than the OEM flywheel?

A: The ACT XACT Prolite chromoly flywheel weighs 8.5 lbs. The OEM cast-iron flywheel in Subaru WRX applications typically weighs between 18 and 22 lbs depending on the model year and clutch size. The Prolite flywheel therefore removes roughly 10 to 13 lbs of rotating mass from your drivetrain. That reduction in rotational inertia translates into faster engine RPM response, quicker rev matching during downshifts, and marginally improved acceleration by reducing the energy the engine must spend spinning a heavy flywheel. The tradeoff is that idle quality and low-RPM smoothness may be reduced compared to a stock flywheel, which is normal and expected with any lightweight flywheel upgrade.

Q: What is the torque capacity of the ACTSB12-HDG6, and will it hold up to my tune?

A: This kit is rated at 574 ft-lbs at the crank, which is approximately 78% over the OEM torque rating. For reference, a stock 2015-2021 WRX produces around 258 ft-lbs at the crank, and a heavily modified Stage 3 build on E85 fuel might reach 400 to 450 ft-lbs at the crank. The 574 ft-lbs rating provides significant headroom above even aggressive tunes on the FA20 platform. For FA24-equipped 2022-2025 WRX builds, which start at a higher baseline torque figure, the same reasoning applies. If your build is approaching or exceeding 500 whp with a heavily modified FA24 and you are concerned about margin, consider the ACTSB12-XTG6 at 681 ft-lbs. Torque capacity ratings are at-crank figures; multiply your wheel torque by approximately 1.15 to 1.20 (accounting for drivetrain loss) to estimate crank torque for comparison purposes.

Q: What is the break-in procedure for the ACTSB12-HDG6?

A: ACT recommends a dedicated break-in period for all ceramic clutch kits, and this kit is no exception. For the first 500 miles after installation, avoid aggressive launches, full-throttle clutch dumps, and sustained slipping of the clutch. The goal is to gradually seat the ceramic friction material against the pressure plate and flywheel surfaces through progressive heat cycling. Begin with gentle, smooth engagements and progressively allow more aggressive driving as the miles accumulate. During the break-in period you may notice some additional odor from the friction material; this is normal. After break-in is complete, the clutch will reach its full rated torque capacity and provide the sharp, positive engagement characteristic of a ceramic race disc. Skipping or shortening the break-in period risks glazing the friction surfaces, which permanently reduces clutch performance and may void the warranty.

Q: How difficult is installation, and do I need any special tools?

A: Installing this clutch kit requires dropping the transmission, which is a significant job on the Subaru WRX platform due to the AWD drivetrain layout. A qualified transmission or drivetrain shop with Subaru experience is strongly recommended. The kit includes an alignment tool (AT90) to properly center the disc during installation, which is required before the transmission can be reinstalled without damaging the input shaft splines. No special machining of the flywheel is required when using the included ACT XACT Prolite flywheel. If you are replacing a prior clutch kit, ensure all mating surfaces on the transmission bellhousing are clean and free of debris before installation. Torquing the pressure plate bolts to the manufacturer-specified value in a cross-pattern sequence is critical for consistent clamp load and long-term reliability. Plan for a full day of shop time at minimum, and verify your release bearing fork position before buttoning up the bellhousing.

Q: Can this clutch kit be used on a daily-driven WRX, or is it strictly for track use?

A: The ACTSB12-HDG6 carries a race designation due to its 6-pad cerametallic disc, and ACT does not recommend race-configuration kits as a primary street clutch for daily commuting use. The ceramic friction material engages more abruptly than an organic disc, which can make low-speed maneuvering and traffic driving noticeably more demanding on technique. If your WRX sees a mix of occasional track days and occasional street miles, this kit is a reasonable compromise, particularly because the sprung hub helps soften some of the harshness at low speeds. However, if your primary use case is daily commuting with only occasional performance driving, the ACTSB12-HDSS (organic street disc) will provide a far more livable daily experience while still upgrading torque capacity and adding the Prolite flywheel. Choose this kit when performance driving is your primary use case.