Project VA WRX: Upgrading the Brakes with Stoptech Part 2 – Getting it Done!
In our last edition of Project VA WRX we showcased some of the preliminary testing involved for the design validation of our new big brake kit by Stoptech. A baseline for the stock brake system was established using Stoptech's test protocols. The brake testing establishes the brake balance, stopping distances and fade characteristics of the stock brakes so improvements can be measured and there is a record of the validation testing.
In testing, the car's ABS and stability controls must work properly and their function is measured and recorded. The new brake system cannot detract from the function of these controls and Stoptech's testing is designed to validate this. If you haven't read it already, click on the link below and read about Stoptech's baseline testing.
Our VA WRX brake kit features Stoptech's ST40 front calipers. The ST40 is a fixed 4 piston radial mount caliper which is great for light and medium weight cars. The ST40 is lightweight and stiff with a forged aluminum body. It is amazingly 4 lbs lighter than the stock two piston sliding caliper even though it has a lot more brake pad area and is cable of much more even distribution of clamping force on the larger pads.
The ST40 caliper has a bolted in place stiffening bridge assembly that prevents the caliper from flexing outward, making it perhaps the stiffest caliper on the market. This helps ensure a hard pedal and even pad wear.
One thing we love about Stoptech brake kits is that they always have correct hydraulic proportioning. Stoptech engineers their brake systems to maintain the same piston area ratios as stock so the pedal travel, front to rear proportioning, ABS and stability controls are not impacted. With today's modern electronically enhanced vehicle dynamics this is pretty important. Stoptech also staggers piston diameters with the smaller pistons forward to reduce taper wear of the brake pads as leading edges tend to wear out faster.
The ST40 calipers feature replaceable stainless steel abutments for shielding the soft aluminum body from the steel pad backing plates. Without the abutments the backing plates would dig into the aluminum of the caliper body. ST40 calipers also feature high temperature silicone rubber dust boots. Most racing calipers remove the dust boots as they tend to burn up during track use but this affects long term seal life on the street. Silicone boots are a good compromise for a dual use calipers as they can tolerate much higher temperatures than regular rubber seals.