ACT 06-25 Subaru WRX HD/Race Sprung 6 Pad Clutch Kit

Turbo Subarus eat clutches, and a tuned WRX, Legacy GT or Forester XT will usually slip the factory 230 mm unit long before anything else gives up. The ACT SB12-HDG6 pairs ACT's Heavy Duty pressure plate with a 6-pad sprung ceramic race disc and a lightweight flywheel, stepping the clutch up to 240 mm for drivers who launch, rally-cross or run serious boost. It is not for the STI, which uses a different six-speed and clutch.

What the clutch kit does in a turbo Subaru

All-wheel drive means a hard launch loads the clutch with the full grip of four tires, so heat and shock are the enemy. ACT rates SB12-HDG6 at 574 ft-lb at the crank, 86 percent over the factory clutch. The SB020 Heavy Duty diaphragm plate raises clamp load, and the 6-pad ceramic disc (6240518) keeps a sprung center to protect the gearbox from driveline shock. ACT's SB12 family upgrades the original 230 mm clutch and flywheel to 240 mm, so the kit includes the XACT Prolite flywheel 600895 to match the larger disc.

Compared with the sibling SB12-XTG6 Xtreme kit, this Heavy Duty version trades some torque capacity for noticeably lighter pedal effort; ACT quotes 15-40 percent more effort than stock for Heavy Duty plates versus 50-80 percent for Xtreme.

Symptoms that point to this kit

• Revs climb without acceleration in third or fourth at peak boost
• Slip after a tune, turbo swap or ethanol fuel upgrade
• Burnt friction smell after launches or track use
• Judder on takeoff from a heat-spotted disc
• Release bearing noise with the pedal down

How to confirm before you buy

Pull in fourth gear from around 2,500 rpm to redline and watch the tach against road speed. A sudden flare at peak boost is classic disc slip. Also confirm the pedal returns fully and the hydraulics are not holding the clutch partly released. Our slipping diagnosis guide covers the checks, and WRX clutch replacement cost by generation breaks down labor by body style.

Fitment

ACT's application chart lists SB12-HDG6 for the 2006-2014 Impreza WRX, 2015-2026 WRX, 2005-2009 Legacy GT including spec.B, 2010-2012 Legacy 2.5GT, 2005-2009 Outback XT, 2006-2008 Forester XT and the 2006 Baja Turbo. It does not fit the US WRX STI. Because the WRX changed engines and gearboxes over these years, send us your year and VIN if your car has had a transmission swap. For a smoother daily driver, the SB12-HDSS street kit uses the same plate with an organic disc.

Install notes

• Kit contents per ACT: Prolite flywheel 600895, pressure plate SB020, disc 6240518, pilot bearing PB1004, release bearing RB846 and alignment tool AT90. M8-1.25 x 16 mm pressure plate bolts are included.
• Replace the pilot bearing with the supplied one and inspect the fork, pivot and rear main seal before assembly.
• Clean the flywheel face, center the disc with the tool and torque pressure plate bolts in a star pattern (ACT lists 26 ft-lb for M8 x 1.25).
• Bleed the clutch with the brake fluid grade on the reservoir cap. See how to bleed a hydraulic clutch.
• A replacement ACT SB020 pressure plate is sold separately if you service the kit later.

Does SB12-HDG6 fit the WRX STI?

No. ACT lists it for the WRX, Legacy GT, Outback XT, Forester XT and Baja Turbo, not the US STI six-speed.

Why is a flywheel included?

The SB12 kits upgrade the factory 230 mm clutch to 240 mm, so ACT supplies its XACT Prolite flywheel 600895 to match the larger disc.

How does it compare with SB12-XTG6?

Both use 6-pad ceramic race discs. HDG6 is rated 574 ft-lb with a Heavy Duty plate and lighter pedal; XTG6 is rated 681 ft-lb with the stiffer Xtreme plate.

Does one kit really fit 2006 through 2026 WRX?

ACT's application chart lists it across those years. Gearbox swaps are common on these cars, so send us your year and VIN if the transmission is not original.

What break-in does a 6-pad race disc need?

ACT says race discs only need a few hard slips to lap in. Avoid overheating it during that process.

Will pedal effort go up?

Yes. ACT expects 15-40 percent more pedal effort from a Heavy Duty plate, depending on the car.

• How to Diagnose Transmission Slipping
• Shift Flare vs. Slip: How to Tell Them Apart
• Automatic vs. Manual Transmission Repair Cost