Subaru Impreza Tuner

Brakes

Brakes from the factory have ample braking power and very good stopping distances.

Front:

2 Piston
Impreza 10.9-in. ventilated discs - 277mm
Crosstrek 11.5-in ventilated discs - 292mm

Rear:

1 Piston 10.8-in. solid discs with parking brake drum - 274mm

Brake Fluid

A good place to start with brakes, coming from a completely stock setup, is to replace the brake fluid with a heavier spec. In my case, when I first began driving spritedly, it was a big scare when I found out that brakes, when run hard, can fade, and lose response. This is a scary moment when you realize fun, must be met with safely. To save anyone from mistake, I would recommend upgrading your fluid from the DOT 3 (standard) to DOT 4 (higher temperature rated). Let's continue.

Poor man's OEM+ front big brake upgrade for the Impreza (2012-2016)

Larger Rotors, better pads, lighter wheels

TLDR; Crosstrek owners have it lucky with standard large front brake rotors, Impreza owners looking to beef up their braking can use Crosstrek parts for better stopping power.

WRX/crosstrek sized front rotor vs Impreza front rotor (right)

For reference: 2012-2016, 2017+ All Imprezas models have 10.9" (~275mm) front rotors. All crosstreks and only the 2017+ Impreza Sport models use 11.6" (~295mm) front (wrx sized) rotors.

By using larger front caliper brackets and rotors, the tuner can increase stopping power. This is basically a simple straight forward upgrade to any Impreza owner. If you want to go 4pot wrx, the cost is significantly more ($600+) without much more benefit. This upgrade still utilizes the same front 2 pot brake calipers found on all crosstrek/Imprezas. Fitment is OEM, should clear even 16inch wheels.

Calipers brackets:

Taken from the Crosstrek 2013-2017, these are used to handle a larger diameter rotor. Approximately $50 per side.

Part numbers:

Left side - 26225SC030
Right side - 26225SC020

Rotors:

I used KNS blanks rotors made by DBA, basically a beefy T3 rotor with the kangaroo vanes and high carbon iron minus the fancy slots and colour changing heat paint. Weight difference between OEM front Impreza rotors and these DBA rotors is a whopping 1100g or 2.45lbs! That's a lot more thermal capacity. As stated above a 20mm increase in size will provide extra brake torque aka stopping power. Of course you can choose your own based on your budget.

Brake pads:

I chose Project Mu B-Spec pads. They have 0-500c and 0.32-0.45u rating, almost double the heat rating compared to OEM. I thought I needed the OEM shims, but found the caliper was too tight, so no shims are needed. Bonus is getting the Project Mu blue backing plate showing through 😎

Thoughts:

Even though the OEM brake system was very good for daily driver stopping, the goal of this setup is to increase the ability to handle heat during spirited, canyon carving or downhill runs. We shall see if the extra 1.1kg of rotating mass per front wheel is worth the trade off. The extra brake torque should also theoretically increase stopping power. Hopefully acceleration and brake bias isn't too far off from stock. I'll obviously have to get used to the new pads as they are grippier than the oems.

If you are an Impreza owner ready for a rotor and pad service, it's as simple as attain 2 front brackets, and larger front rotors. The rest is the same. I hope this helps others.

Update: The use of brake shims (brake pad backing plate) is needed. After some time, when the pads wear down enough, there will be enough room to fit the backing plates with the brake pads. The OEM backing plates include a sort of shim which helps deaden brake vibration noise. I have enjoyed solid street braking performance with this setup.

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