Subaru STI Best Clutch Options

How to Choose the Best Clutch for your STI

This article will help guide all 2004-2021 Subaru WRX STi owners to the best matched clutch kit for their build and driving style. Whether you are planning your first power mods or your STi is already making big power with an aftermarket turbo we have the perfect clutch kit to support your project. If you’re looking to make more power from your STi have a read through: Best Modifications STI EJ25. Below are the top 3 clutches for high power STI builds. The Twin Disc option is ideal for long life with maximum TQ holding ability while the FX400 is the ideal “street use” single disc clutch option perfect for an STI making 400-500WHP.

We at Brewed Motorsports have used and tested clutch kits from every major manufacture on the market. Over all the years of testing we have consistently had the best and most reliable results using Clutch Masters and Exedy. With over 15 years of hands on experience using the full Clutch Masters line up on a huge range on WRX and STI builds we are confident CM has the best clutch options for any STi build. For those who would like to use another brand we recommend Exedy Clutches from our partners at FFrides. For us, Clutch Masters has been our go-to for clutches due to their high quality made in USA construction, reliability, long life, serviceability, and easy to source replacement parts. Exedy comes in a close second only due to the limited friction materials and lack of easy to source replacement parts.

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Best STi Clutch Stock Power/light mods

If you’re driving a stock or lightly modified STi and want better clutch performance/holding power with OEM pedal feel, Clutch Masters FX100 is perfect for you. This Clutch is super driver friendly with OEM like engagement and super smooth feel with the ability to hold 15% more torque than the OEM clutch.

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Stage 1-3 STi Clutch

Once your STi has some more “serious mods” such as: STi Cobb Accessport, STi Cobb Boost Controller, STi Front Mount Intercooler, and a custom STi E-tune an upgraded clutch is key to reliably holding the power. At this power level (around 350hp) we highly recommend the FX200 and FX350 clutch kits. Choosing between the FX200 – FX300 is really dependent on what the driver wants most out of their clutch as to pedal feel and initial bite. 

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STi FX200 Clutch

While having similar pedal feel to the stock clutch and FX100, will not only hold 20% more torque but also last 2-3 times the longer due to the Kevlar clutch disc material. The FX200 is the ideal clutch for bold on mods + custom E-tune for anyone that wants a super long life clutch that has a nice soft smooth pedal feel.

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STi FX250 Clutch

With the FX250 clutch you will have similar pedal feel to the FX100 and FX200, while using Clutch Masters custom “Fiber Tough” friction surface for slightly higher torque holding capacity while also being street-able. This is a slightly more aggressive friction material than the FX200 and is perfect for those that want a solid/fast engagement on hard shifts.

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STi FX300 Clutch

The FX300 is our last option when it comes to an oem like “street-able” feel for a single plate clutch kit. The FX300 has slightly more torque holding capacity than the FX250 as well as a slightly more aggressive engagement. This is one of our most popular Clutch kits for any STi making 300-400HP. The FX300 is soft enough to use in a daily driver but holds up great to weekend track days, autocrosses and the occasional drag racing. 

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Motorsports Stage 3+ STi Clutch Options:

If you find yourself in this category you probably have one of our Built IAG Blocks and running our custom Cobb AP E-tune or our STi Haltech ECU package or STi Motec ECU package. There’s really only 4 good options if you’re using your STi for serious competition racing and motorsports. These 4 options are the FX350, FX400, FX500, or one of Clutch Masters Twin Disk clutch kits. The aforementioned clutch kits hold up to 40% more torque and offer a super fast on off engagement with stiffer than stock pedal feel. They will have some chatter, aggressive engagement, and are not normally recommended for street driving. 

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STi FX350

The FX350 is our first step into clutches designed for racing. The FX350 offers decent pedal feel with only some light clutch chatter. These Clutch discs feature the Fiber Tough material and increased rigidity, this is one of the more driver friendly clutch kits when it comes to single plate clutches that are meant for motorsports use. 

 

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STi FX400 6 Puck

The FX400 is one of the first clutch kits with a ceramic friction surface. With this you can expect increased torque holding capacity over any aforementioned clutch kits. You may also experience chatter in reverse and very quick engagement. This sprung 6 puck design being one of the more aggressive clutch discs compared to the segmented version.

 

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STi FX400 Segmented Disk

This clutch kit has a similar torque holding capacity of the 6 puck version, but with this full face design you can expect smoother engagement in first gear and reverse compared to the 6 puck version of the FX400. This full face sprung clutch disc is one of the best options for those who want super fast engagement but a smooth enough feel to daily drive.

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STi FX500

This is the most aggressive single disc clutch kits that Clutch Masters Offers. This is certainly recommended for race only due to the un-sprung 6 puck clutch disc. This is the ultimate single disc for your STi setup for racing and ready to hold up to 600+hp!

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725 Series Twin Disc Clutch STI

The 725 series (race or street) for the EJ25 STi is the ultimate clutch kit for anyone making serious power. Clutch Masters 725 race series clutches will support 1000+ hp with no issues. The biggest thing to consider when choosing your twin disc Clutch Masters for your STi is deciding if you would prefer the Street or Race version. We at Brewed highly recommend the street twin disk kits are used for street driven vehicles, especially if AWD. The Racing kit will have a fast/stiff engagement due to the 2 ceramic clutch discs vs the street kit having one organic and one ceramic disk.

STi Twin Disk Clutches:

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Service and Tips:

We also offer Clutch Masters Clutch Lines to to replace the factory soft lines for more precise pedal engagement. This is a must have upgrade for any older STI as the factory rubber clutch line is prone to failure over extend use/heat cycles.  

We offer two versions of Clutch Masters pressure plates for the STi 6 speed specifically, the normal “Heavy Duty” kits and the “High Rev” kits. The difference between the “High Rev” pressure plate and the standard “Heavy Duty” pressure plate is the High Rev kits have an even stronger and reinforced pressure plate to withstand higher RPM’s for your built EJ25’s.

If you need additional help choosing the correct clutch kit for your EJ25 Subaru give us a call! For a complete run down of all the CM clutches and applications checkout: Clutch Masters Clutch kits explaining all the Clutch Masters models/offerings.

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