Project VA WRX: Upgrading the Brakes with Stoptech Part 2 - Getting it Done!

by Mike Kojima

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. 

Read about Stoptech's brake system validation process here!

Read more about Project VA WRX here!

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.   
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Wednesday, October 28, 2015 8:14 AM
Ah... jealous the rear BBK is compatible with the stock parking brake. Wish that were the case on the S2000 where the rear brakes run extremely hot and the BBK would be a huge improvement.
Wednesday, October 28, 2015 11:44 AM
The parking brake on Subarus is a drum, so changing the caliper doesn't matter.
Thursday, October 29, 2015 1:35 PM
have you tried the vented rear rotors the Urge makes for the S2000? could make for a good article here :D

(sorry for hijack)
Scott Helmer
Scott Helmerlink
Saturday, October 31, 2015 12:04 AM
Almost completely off topic, but 7075 is a great material, and I must say I like the use of it in the this brake package. I have a 45 pound block cut from a large billet of the T651 version that I acquired as a temp worker at an aerospace parts supplier in Tukwila, WA a few years ago, and it still astounds me at just how BIG that block is, considering the weight (which is to say, of course, that considering how strong that particular aluminum is, it's surprisingly light). I wish I could afford to do something with it, as I would love to cut chips out of it and make something, but my that block has been handy as an impromptu vise and doorstop so far!

Anyway, sorry for the hijack, back to your regularly scheduled program of automotive awesomeness!
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