Subaru Impreza's are one of the more popular vehicles we offer brake and coilover kits for. Despite the stock front 4-pot and rear 2-pot calipers already offering decent stopping power, there is still a lot of room for improvement by upgrading to larger calipers, 2-piece vented rotors with aluminum hats, high friction pads and braided brake lines.

First up is our very own 2005 GDA WRX running a front 330mm 6-pot and rear 330mm 4-pot brake setup and PB coilovers with pillowball mounts all-round. Wheel camber is set to 3 degrees front and 2 degrees rear.

This is another '05 GDA that belongs to Wheels Asia magazine in Singapore, who were kind enough to review our products in 2013. They installed the same coilover kit with front 8kg and rear 6kg springs, but as they are running 18" wheels and have a little extra space to play with, they opted for our larger front 356mm big 6-pot brake kit.

You can read the full brake and coilover reviews here.

Here is another GDA WRX that recently underwent a rear brake upgrade; a 330mm 4-pot kit with drilled and slotted rotors and purple calipers. Not to everybody's taste but each to their own.

Finally we have a more recent GRB STI in Japan. This customer went one step further and purchased a massive front 356mm 8-pot and rear 330mm 6-pot combination. Slightly overkill for a street car, but at least you're never going to be short of stopping power when you need it.

We have been experimenting to find the best brake setup for the GDA WRX over the years and have tried various options, both on brake bias calculators and real-world race situations.

The stock bias on the GDA is front 69% and rear 31% or a ratio of 2.21, so the idea is to get a close as possible to those figures without increasing the piston surface area by too much. The best way to increase torque is by increasing the diameter of the rotors.

We have come to the conclusion that the best setup is a front 345mm big 6-pot and rear 330mm 4-pot. This allows a bias of front 70% and rear 30% or 2.36, which is 1% out compared to the stock settings, but well within the acceptable range once you account for passengers or other items that can throw off the weight balance. When combined with our sport pads, that setup increases the brake torque by 91% at the front-end and 79% at the rear-end. The total piston surface area on each of these calipers is about 10% more than the stock pistons. We would normally say you should try to keep them within +/-5%, but that depends on the vehicle. t Fortunately the stock master cylinder on the GDA can handle the extra surface area, and the pedal remains solid with minimal travel.

However, that combination requires either 18" or very large 17" wheels to fit them in, so they aren't suitable for everybody. If they don't fit then the next best option is a front 330mm big 6-pot and rear 330mm 4-pot which is actually the closest you can get to stock bias with a F/R ratio of 2.24. Having said that we would still recommend the larger front 345mm rotors for the gains in cooling / brake fade prevention, and the fact the extra front-end bias simply feels more stable and less tail happy when braking hard into corners.

The issue we had with our car is the wheels were still not big enough to encompass the big 6-pot calipers. The best solution for this would be to use smaller 304mm rotors on the rear, but unfortunately the smallest we can make for the GDA are 330mm, anything smaller than that and there isn't enough space to fit the caliper brackets. So we were forced to install the medium 6-pot calipers instead, in which the total pistons surface area is actually 4.9% less than the stock calipers. That's not really a problem as with the front rotors being 36mm larger than stock, we're still gaining 55% more torque compared to the OEM front brakes.

The problem we have now is that we have altered the brake bias so that it's too rear-heavy at 66/34% or 1.91. That's a little bit too much for comfort, but there is a very simple way to rectify this issue, and that's to use sport pads with 0.45u friction on the front and street pads with 0.40u on the rear. That brings the bias back to 68/32% or 2.15 which is close enough to stock for our liking.

If you have any further questions regarding brake or coilover kits for the Subaru Impreza, or any other application, just drop us an email: