Upgrading the WRX brakes with StopTech
Stoptechs ST40 caliper has a forged aluminum body which gives the caliper a strong stiff structure.  Stiffness gives better pedal feel.
The ST40 front caliper has 4 pistons of differing diameters to prevent taper wear of the pads. Brake pads tend to wear faster on the leading edge and develop a tapered wear pattern from front to back. The ST40 uses smaller leading edge pistons and larger trailing pistons, so there is more clamp force on the trailing, slower wearing tail of the pads and less on the fast wearing leading edge. This assures even wear and longer pad life. Stoptech calipers also have dust boots made of high-temperature silicone. Most racing type calipers don’t have these, as they tend to burn up in track use. For street use, having no dust boots affects service life. The calipers have stainless steel abutments to protect the forged aluminum body from the wear of the brake pad backing plates. Without them, the backing plates can wear grooves into the alloy body which can cause sticking and inconsistent action.
Our Stoptech kit’s rear rotor has all the same design features as the front rotors with an exception. The stock rear brakes have a drum-type parking brake so the drum is integrated into the rear alloy hat. The hard anodized surface is fine for use as a parking brake but please don’t do e-brake intitations with these or the soft aluminum will get torn up.  The rear rotors are also 328mm by 28mm.  The rear rotor is also 14 lbs like the front.
The rear caliper is Stoptech’s ST22 caliper which is a two-piston caliper that shares most of the same attributes as the ST40 front caliper.
The rear caliper has silicone dust seals and stainless pad abutments for long life on the street.


  1. You are spoiled with your dry California weather. it looks easy when everything still has factory paint. Trying to do this and the suspension bushings on a similar car here in the northeast would involve torches, penetrating oil, and lots of strong language.

  2. I need a press, lathe and mill… And as DedBull noted, less rust! Sweet upgrade, fingers crossed it will last a long time for you.

  3. Will you be tracking this car? I did 20 track days on an ’04 WRX and found the pad knockback on stock brakes and street tires substantial. A larger diameter rotor will mean larger deflections and more knockback. I was considering going BBK but then the pad knockback plus tracking a car with 60% of the weight in front made me realize it would be cheaper and more fun to do the E36 M3 route. I only miss the WRX on the track when it rains.

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