XClutch 15-21 Subaru WRX STi Base 2.5L Stage 1 Steel Backed Organic Clutch Kit
The XClutch XKSU24001-1T is a single-disc Stage 1 clutch kit for the 2015-2021 Subaru WRX STI with the EJ257 and six-speed manual. It is aimed at the owner whose factory clutch has started slipping in the upper gears, chattering on takeoff or squealing from the release bearing, and who wants something that drives like stock but holds the extra torque of an intake, exhaust and a mild tune. What sets the 1T apart from XClutch's other Stage 1 STI kits is the disc construction: the organic facing is bonded straight to a steel backing plate instead of being riveted to wavy cushion springs.
The STI routes all of the EJ257's torque through a pull-type clutch into a six-speed with a driver-controlled center differential, so the clutch is the one place in the drivetrain that is allowed to slip. XClutch rates the 1T kit at 420 ft-lb of torque capacity including its safety factor, with 35 percent more clamping force than the factory pressure plate. The disc is 9 7/16 in, organic, with a sprung hub to soak up driveline shock, on a 1 in, 24-spline input shaft.
XClutch says bonding the organic material directly to a steel disc improves burst strength in performance cars. In plain terms, the friction material is far less likely to come apart at high rpm or under repeated hard shifts than a riveted facing. The trade-off is that a steel-backed facing has no cushion between the friction faces, so engagement is a little more direct than a fully cushioned organic disc, though still meant for street use.
The kit includes the pressure plate, disc, release bearing, pilot bearing and an alignment tool. It does not include a flywheel.
A slipping clutch does not set a trouble code. Boost leaks and fueling faults can feel like slip, so scan and clear engine codes before condemning the clutch.
In fourth gear at around 2,500 rpm, go to full throttle and watch the tachometer against road speed. If the needle jumps ahead while the car barely accelerates, the clutch is slipping. Before you order, check the hydraulics: XClutch's own pedal bulletin points out that a master cylinder pushrod with no free play holds pressure on the system and can cause premature slip, and that the slave cylinder should push back by hand. Our slipping diagnosis guide walks through the checks, and the manual vs. automatic repair cost guide helps you budget the labor.
Our listing covers the 2015-2021 Subaru WRX STI 2.5L, Base and Limited. XClutch's compatibility table for XKSU24001-1T also lists the 2015 Launch Edition, 2016 Series.HyperBlue, 2018 Type RA and 2019 S209, the 2004-2014 Impreza WRX STI 2.5L, the 2007-2009 Legacy GT spec.B, and 2.0L EJ207 STI models from 2001-2013. It does not fit the non-STI WRX, which uses a different transmission and clutch. Swapped cars should be checked by gearbox, not model year, so send us the year and VIN if you are unsure.
If you want a softer cushioned Stage 1 disc for the same car, see the XKSU24001-1A sprung organic kit. For big-turbo builds past what a single disc can hold, the 10.5in twin organic XKSU23531-2A is the next step.
| Brand | XCLUTCH |
| Part number | XKSU24001-1T |
| Fits | XClutch 15-21 Subaru WRX STi Base 2.5L Stage 1 Steel Backed Organic Clutch Kit |
| Vehicle fitment | Subaru Wrx Sti (2015-2021) |
| Type | Clutch Kits - Single |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Both are XClutch Stage 1 organic kits for the STI. The 1T bonds the organic facing directly to a steel backing disc for better burst strength. The 1A uses a conventional sprung organic disc with a cushioned facing for softer street engagement.
XClutch rates XKSU24001-1T at 420 ft-lb of torque capacity including its factor of safety, with 35 percent more clamping force than stock. That suits a lightly modified street STI, not a big-turbo build.
No. The kit includes the pressure plate, disc, release bearing, pilot bearing and alignment tool. Resurface the factory flywheel or fit a new one.
No. It is built for the STI six-speed with its pull-type clutch. The non-STI WRX uses a different transmission and needs a different kit.
XClutch recommends DOT 3 or better for street cars and DOT 4 or 5.1 for performance driving. Never use DOT 5 silicone fluid.
Drive gently for the first 1,000 km, about 620 miles, using low-rpm engagements and avoiding launches or long slips so the facing beds evenly to the flywheel.
