In the brake system, there is an important part named proportioning valve. When you do brake, the all weight shifts to the front part of your Subaru, and brake drum generates pressure and pedal is getting force, so the proportioning valve is designed to reduce the rate of pressure to the force, which stops the rear part of car from locking up. In this way, if your rear wheels easily lock up, especially on wet surfaces, then there is something wrong with your brake proportioning valve. You need to find a new replacement to cover the old one as long as you find you safety is not assured when you are driving your Subaru. You can always find a good brake proportioning valve here with satisfaction. Price is the only thing we would like to reduce, but not the quality. We offer you all Subaru genuine OEM brake proportioning valve.