Both of the DBA rotors have stripes of thermal paint on the outer edge of the rotors. By observing which stripe of thermal paint burns off, you can determine what temperature the rotors reach and choose an effective brake pad for the temperature reached on the track. This practical, cool feature is something we haven't encountered before.
Having good brake rotors means nothing if the operating temperature range of your brake pads is being exceeded on the track. It was obvious that we were right at the edge of the stock pads' effectiveness with sticky tires and increased horsepower at Willow Springs, a track noted for being easy on brakes. At any other track the brakes would probably fade into oblivion. Although the car sees track use, it is also a daily driver, so having a brake pad with a wide effective temperature range was also a must. For help and advice on all things braking, we turned to our friend and supplier of brake pads for our race team: Monty Holt of Bits and Pieces Motorsports.
Monty recommended the Hawk HP+ brake pad. For our road racing program we use Hawk products supplied by Monty exclusively and have always been impressed by their performance and durability. The HP+ is a semi-metallic formula modified with the addition of iron and carbon powder. This gives it a consistent coefficient of friction over a wide range of temperatures. The HP+ can still stop while cold and works well enough when hot that it can be track driven, especially with a car with large factory brakes like the STi that just needs a little help to prevent fade.
To improve pedal feel, Stoptech supplied some of their braided steel brake lines. The lines have a chemically inert Teflon inner hose covered by a reinforcing ply of woven stainless steel. This combination is very resistant to ballooning under pressure, unlike the stock rubber lines; thus every bit of brake pedal travel goes to moving the pistons in the calipers. We were surprised how much difference these lines made. The pedal feels rock solid like a real racecar - impressive considering the stock pedal feel was quite good as well. The car's ABS system seemed to like it as well, seemingly cycling faster with a higher resolution. We don't know if that's true or not, but our seat of the pants told us so. Finally, to help protect the braided steel from debris damage and to prevent the rough steel braid itself from abrading parts of our car, the outer hose is covered with a layer of smooth PVC, a nice added feature.
The Stoptech brake lines are DOT registered and meet all performance requirements set by the DOT. Many braided steel lines are not, and one of the long-term issues could be that the steel braid fatigues and breaks. To receive DOT compliance certification, lines must pass the dreaded whip test amongst a host other performance tests for the lines and components. Although braided steel lines are very strong, they have traditionally had a very hard time passing this test. During the whip test the brake line is mounted by one end to a rotating fixture and spun at a certain rpm for a given time. The brake line cannot fail during the test period. Stoptech lines have a molded plastic reinforcement around the end fittings that reduces the fatigue of the line in this area, allowing it to easily pass the whip test. We also noted the quality of the fittings and the superior fit of the Stoptech parts in general. This is a welcome change after many years of jury rigging most braided brake line kits with zip ties, Adel clamps and other devices to get a safe fitment. It's refreshing that the Stoptech lines simply slide right in with no hassles or fiddling around.
Lastly, we replaced our stock, stale, never-been-changed-before, Japanese fish oil brake fluid with Motul RBF 600. Motul's RBF formula is one of the best fluids, performing nearly as well or better as ber-expensive exotic stuff like the legendary F-1 brake fluid standards Castrol SRF and AP650. When brake fluid gets really hot it boils. Boiling fluid has bubbles in it that are filled with compressible gas. The compressible gas causes the brake pedal to drop to the floor. This is another type of brake fade that must be avoided.
Motul's dry boiling point is an amazing 600F. Motul works so well that our team's racecars need only bleed the brakes once a season, instead of the typical once a race. Most brake fluids absorb moisture from the atmosphere. When the brake fluid absorbs moisture, its boiling point rapidly drops - rendering it less effective. Even though the brake fluid is contained within the brake system, it still can quickly absorb a surprising amount of moisture from the atmosphere that is inadvertently drawn into the brake system. Some brake fluids can deteriorate greatly from this phenomenon with as little as one heat cycle of the brake system. Motul resists absorbing moisture from the atmosphere better than most brake fluids, so its inherent high boiling point lasts longer than most fluids. If you do manage to boil Motul, surfactants in the formula cause the bubbles formed to rapidly dissipate, and you get a recovery of your brake pedal feel.
The change to the feel of our modified brakes is confidence inspiring. The brake pedal is now firm and high. Modulation of the brakes is now much easier due to the improved pedal feel. Under track conditions we are not observing any fade at all. The only negative is a slight amount of brake squeal for the first few minutes of operation on the street when the pads are dead cold, an acceptable trade off for greatly improved fade resistance. From our initial track test it appears as if our brake pad life is greatly improved as well.
Our last mod for this installment is the addition of Whiteline's front and rear Strut Tower Braces. Although the STi has a strong WRC inspired chassis that exhibits good rigidity to begin with, like most cars it responds to an increase in stiffness. The Whiteline braces are made of aircraft aluminum alloy with brackets that are designed to place the brace in an area that does not interfere with the Whiteline Group 4 struts damper adjustment. Despite the stiff chassis, we noted a difference in the car handling. Steering response is slightly improved and the ride is also improved, a sure sign that the braces are working well. We also noticed that the car is now more sensitive when it comes to making adjustments to the damping and swaybar stiffness. This is another sign that the bars are doing their job.
We felt that the rear bar surprisingly seemed to make a bigger difference than the front bar did. Although the braces did not make a huge world of stopping difference, they did make a positive contribution to Project STi's handling and are the icing on the cake rounding up what has become a very good handling car that also has decent road manners to boot.
In our next installment we're going to address our weak clutch with some trick parts from ACT; improve cooling with some stuff from ARC; and get even more power with the help of a turbo from Forced Performance and some complementing parts from Perrin. Project STi is getting ready to wreck havoc on the track and teach Project EVO a lesson in speed. Stay tuned for more.