Clutch Masters 04-11 Subaru WRX/STi 2.5L Turbo 6-Spd FX350 Sprung Fiber Clutch Kit
Clutch Masters 15017-HDFF is the FX350 kit for the Subaru WRX STI with the 2.5L turbo and six-speed gearbox, listed here for the 2004-2011 cars. It suits the STI owner whose car now makes noticeably more boost than stock, who drives it every day but also runs autocross or a few track days a year, and whose current clutch is slipping or fading from heat. It sits between the comfortable street kits and the puck-style race kits in the Clutch Masters range.
The STI's clutch has to grab the full surge of torque when the turbo spools, then survive repeated hot launches. The FX350 pairs the Clutch Masters Power Plus I high-leverage, heavy-duty pressure plate with a disc faced in their Fiber-Tough friction material, cut into segments and bonded to a steel backing. A Marcel spring wafer sits under the facings and the hub is sprung. Clutch Masters lists a 110 percent increase in holding capacity and describes it as holding slightly more than its FX300 Kevlar kit.
The trade-off is engagement. Clutch Masters is upfront that the FX350 engages a little more aggressively than the FX300 and will produce some chatter, which is the price of a material built to tolerate heat that would glaze an organic disc. Fiber-Tough is their answer to the old choice between a clutch that drives nicely and one that lasts under abuse; it aims to give you most of both. Expect a firmer bite point than stock and some shudder if you slip it pulling away on a slope.
Check the hydraulic side first: fluid level, a damp slave cylinder, and a pedal that returns fully. Partial release slips the disc just like wear does. Then do a controlled pull in fourth from low rpm and watch the tach against the speedometer as boost builds. If engine speed flares, the clutch is slipping. Our guide to diagnosing slipping covers the test, and the automatic vs. manual repair cost guide puts a clutch job in perspective against gearbox work if you also hear bearing noise.
Our listing is for the 2004-2011 Subaru WRX STI 2.5L turbo six-speed. The Clutch Masters application chart for 15017-HDFF is broader: it lists the WRX STI 2.5L turbo six-speed from 2004 through 2021 and the 2006-2009 Legacy GT spec.B 2.5L turbo six-speed. It is not for five-speed WRX models, which use a different clutch. Subaru made running changes over that span and many STIs have had flywheels or transmissions swapped, so if your car is outside 2004-2011 or you are not sure what is in it, send us your year and VIN before ordering. More STI clutch parts are in the rebuild kits collection.
If the car is daily driven with mild bolt-ons, the smoother FX250 kit is the friendlier choice in traffic. If the FX350 is still not enough for a big-turbo build, the FX400 8-puck kit steps up to a puck-style disc at the cost of harsher engagement.
| Brand | Clutch Masters |
| Part number | 15017-HDFF |
| Fits | Clutch Masters 04-11 Subaru WRX/STi 2.5L Turbo 6-Spd FX350 Sprung Fiber Clutch Kit |
| Vehicle fitment | Subaru Wrx/Sti (2004-2011) |
| Type | Clutch Kits - Single |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Some, yes. Clutch Masters says it engages slightly more aggressively than the FX300 and will produce some chatter. It is most noticeable when pulling away slowly or on a hill.
Clutch Masters says the FX350 has slightly more holding capacity than the FX300 and uses Fiber-Tough material instead of Kevlar, aimed at drivers who also take the car to the track.
No. 15017-HDFF is listed for the six-speed WRX STI and the 2006-2009 Legacy GT spec.B six-speed only.
No. Resurface your existing flywheel or buy a replacement separately. The kit includes the pressure plate, disc, release bearing, pilot bearing where applicable and an alignment tool.
The Clutch Masters chart lists the WRX STI six-speed from 2004 through 2021. Our listing is written for 2004-2011, so send us your year and VIN and we will confirm fitment before you order.
