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Heavy Duty Clutch and Lightweight Flywheel Built for the Daily-Driven and Tuned 2006-2025 Subaru WRX
The ACT SB12-HDSS is the ideal complete clutch and flywheel upgrade for Subaru WRX owners who want significantly improved torque capacity with the engagement feel of a street-friendly organic disc. Rated at 449 lb-ft at the crank and built around the upgraded 240mm clutch diameter, the SB12-HDSS pairs ACT's Heavy Duty pressure plate with the Performance Street organic disc and the lightweight 8.5-pound ACT XACT Prolite chromoly flywheel.
The result is a system that handles modified power levels and aggressive street driving while remaining smooth and manageable for daily commuting. Compatible with 2006-2025 WRX models across EJ255, EJ257, FA20, FA24, and JDM EJ25 engines with 5-speed and 6-speed transmissions, the ACT SB12-HDSS delivers the perfect balance of street drivability and performance for the WRX enthusiast.
Key Features
- ACT SB12-HDSS uses the Heavy Duty pressure plate, delivering 449 lb-ft of torque capacity for street-performance WRX builds
- Upgrades from factory 230mm to a 240mm clutch diameter for increased heat dissipation and load capacity
- Includes ACT XACT Prolite chromoly flywheel at 8.5 lbs for reduced rotational inertia and improved response
- Performance Street organic disc with sprung hub provides smooth, progressive engagement for daily drivability
- Exclusive ACT diaphragm design with four-stage heat-treating process for extended clutch life under hard use
- Fits 2006-2025 Subaru WRX excluding STI, with EJ255, EJ257, FA20, FA24, and JDM EJ25 engines
- Compatible with 5-speed and 6-speed WRX transmissions
- Complete kit includes flywheel, pressure plate, disc, release bearing, and alignment tool
- ACT limited warranty included
Fitment
| Year Range | Make | Model | Trim |
|---|---|---|---|
| 2006-2014 | Subaru | Impreza | WRX |
| 2006-2014 | Subaru | Impreza | WRX Limited |
| 2009-2014 | Subaru | Impreza | WRX Premium |
| 2006-2007 | Subaru | Impreza | WRX TR |
| 2015-2025 | Subaru | WRX | Limited |
| 2015-2025 | Subaru | WRX | Premium |
| 2024 | Subaru | WRX | TR |
| 2025 | Subaru | WRX | TS |
| 2005-2006 | Subaru | Legacy | GT |
| 2005-2009 | Subaru | Legacy | GT Limited |
| 2006-2009 | Subaru | Legacy | GT spec.B |
| 2006-2008 | Subaru | Forester | XT Limited |
| 2008 | Subaru | Forester | Sports 2.5 XT |
Specifications
| Detail | Value |
|---|---|
| Part Number | SB12-HDSS |
| UPC | N/A |
| Pressure Plate | ACT Heavy Duty |
| Disc Type | Performance Street Organic, Sprung Hub |
| Clutch Diameter | 240mm |
| Torque Capacity | 449 lb-ft at crank |
| Flywheel | ACT XACT Prolite Chromoly Steel |
| Flywheel Weight | 8.5 lbs |
| Engine Fitment | EJ255, EJ257, FA20, FA24, JDM EJ25 |
| Transmission | 5-speed and 6-speed |
| Hub Style | Sprung |
| Street Use | Yes |
| Warranty | ACT Limited Warranty |
What's Included
- ACT Heavy Duty pressure plate assembly
- ACT Performance Street organic disc (sprung hub)
- ACT XACT Prolite chromoly flywheel (8.5 lbs)
- Release bearing
- Clutch alignment tool
- Mounting hardware
About ACT (Advanced Clutch Technology)
Advanced Clutch Technology (ACT) has been manufacturing high-performance clutch systems in California for decades, building a reputation for precision engineering and unmatched durability across street and competition applications. The ACT SB12-HDSS is part of the new SB12 lineup specifically developed for the 2006-2025 Subaru WRX, combining ACT's most trusted HD pressure plate with the proven Performance Street disc and a lightweight Prolite flywheel in a single precision-balanced kit.
Frequently Asked Questions
What is the difference between the ACT SB12-HDSS and SB12-XTSS for the Subaru WRX?
The SB12-HDSS uses the Heavy Duty pressure plate rated at 449 lb-ft, while the SB12-XTSS uses the higher-clamping Xtreme plate rated at 532 lb-ft. Both use the same Performance Street organic sprung disc and XACT Prolite flywheel. The SB12-HDSS is ideal for mildly to moderately tuned WRX builds; the SB12-XTSS suits more aggressively modified setups.
Does the ACT SB12-HDSS fit the 2022-2025 Subaru WRX with the FA24 engine?
Yes. The SB12-HDSS is compatible with the FA24 turbocharged engine in the 2022-2025 Subaru WRX, as well as the earlier EJ255, EJ257, FA20, and JDM EJ25 engines across 5-speed and 6-speed transmissions.
Is the ACT SB12-HDSS compatible with the Subaru WRX STI?
No. The SB12-HDSS is designed specifically for the WRX and is not compatible with the STI, which uses a different clutch specification. ACT offers dedicated STI clutch kits for that application.
Can the ACT SB12-HDSS be used as a daily driver?
Yes. The ACT SB12-HDSS is one of the most popular street clutch kits ACT produces. The Performance Street organic disc with sprung hub delivers smooth, stock-like engagement characteristics that are comfortable for daily commuting, even with the Heavy Duty pressure plate providing increased clamp load.
How does upgrading to the 240mm clutch in the SB12-HDSS benefit the WRX?
The larger 240mm clutch diameter increases contact surface area between the disc and flywheel, raising heat capacity and torque handling compared to the factory 230mm unit. This makes the SB12-HDSS better suited for modified WRX engines producing power above the factory clutch's reliable threshold.
Does installing the ACT SB12-HDSS require any machining or special tools?
No machining is required. The SB12-HDSS is a direct bolt-on replacement kit. Installation requires standard transmission removal tools and the included clutch alignment tool. Professional installation is recommended due to the complexity of WRX drivetrain service.
What does the ACT XACT Prolite flywheel weigh and what benefit does it provide?
The XACT Prolite flywheel weighs 8.5 pounds and is made from chromoly steel. The reduced weight compared to the factory flywheel lowers rotational inertia, which improves engine rev response and acceleration, particularly noticeable during gear changes and spirited driving.
Is the ACT SB12-HDSS warranted against defects?
Yes. The SB12-HDSS is covered by ACT's limited warranty against defects in materials and workmanship. Warranty procedures and terms are available directly through ACT or your authorized ACT dealer.
Does the ACT SB12-HDSS fit 2006-2014 Subaru Impreza WRX models?
Yes. The SB12-HDSS is compatible with 2006-2014 Subaru Impreza WRX trims including the WRX, WRX Limited, WRX Premium, and WRX TR across applicable engine configurations with 5-speed and 6-speed transmissions.
Installation Instructions
- Safely lift the vehicle and remove the transmission following the WRX factory service manual for your model year
- Remove the factory clutch disc, pressure plate, and flywheel from the crankshaft
- Inspect the crankshaft rear main seal and pilot bearing for wear and replace as needed before installing new components
- Mount the ACT XACT Prolite flywheel to the crankshaft using the provided hardware, torquing to specification
- Insert the clutch alignment tool through the disc center hub into the pilot bearing to properly center the disc
- Position the ACT Performance Street disc against the flywheel with the transmission side facing toward the transmission
- Fit the ACT Heavy Duty pressure plate over the disc and torque the mounting bolts in a star pattern to specification
- Install the included release bearing into the bell housing
- Reinstall the transmission and reconnect all drivetrain, exhaust, and driveline components per factory specification
- Bed in the clutch with light-load driving for the first 500 miles before applying full power
WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.
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