posted on April 18, 2017 15:01
Project EP3 Civic Si, Improving the Brakes with Fastbrakes, Stoptech and Willwood
In the last edition of Project EP3 Civic Si, we explained how we went about converting our car from 4 lug to 5 lug hubs. We did this for two reasons: one to take advantage of the larger selection of 4x114.3 bolt circle wheels available on the market and the other to take advantage of the larger RSX Type-S wheel bearings and axles to stiffen up the bearing system in anticipation of performance fixed caliper brakes and more power from a possible engine swap.
Now that we have the right underpinnings, it is time to go ahead and do the brakes!
For a caliper, we selected Wilwood's forged Dynapro six-piston lug mount. We chose this caliper because it was the biggest and largest pad area caliper that had the 5.25" bolt pattern, so we could use easy-to-get adapter mounts.
The Dynapro also is available with small pistons and piston area, so our brake proportioning would be very close to the factory. The piston sizes are 1.62", 1.12" and 1.12" for an overall area of 4.04 square inches. The stock front brakes have a piston area of about 7 square inches, so there is less hydraulic gain in the caliper than stock.
The reduced hydraulic gain makes for a firmer pedal and is made up for by the greatly increased pad area and the increased mechanical efficiency of having a much larger rotor. This keeps the proportioning in line with stock, which will help keep the ABS system happy.
The Dynapro Caliper is very stiff, having 5 bridge bolts and one substantial bridge formed into place. That in addition to the strong forged body makes for one rigid caliper that delivers a firm pedal and excellent brake feel. The caliper has a brake dust and corrosion-resistant electroless nickel plating for a unique look, easy cleaning and a long life.
The Dynapro caliper has staggered piston diameters to eliminate taper wear of the brake pads. It also has stainless steel pistons to conduct less heat to the brake fluid and stainless abutments on the leading and trailed edges of the pad pocket. This prevents the backing plates of the pads from digging into the soft aluminum caliper body, potentially causing inconsistent action.
For the rest of our brake system, we used a Fastbrakes EP3 big brake kit. We started off with Fastbrakes lightweight two piece rotors. They use a 12.2" in diameter vented friction ring on an alloy hat. Despite being an inch larger than the stock rotors, they are 4 lbs per side lighter than stock.
The hats are machined from 6061 T6 aluminum and are hard anodized for corrosion resistance. The lighter weight is due to the alloy hat taking the place of a standard discs iron center. Having significantly lighter rotors gives better braking and acceleration due to their lower inertia. The light weight also means less unsprung weight, which improves both ride quality and handling as well because the suspension will be more responsive to bumps.
The rotors are vented with radial vanes and have the friction surface slotted to give brake dust and gasses from vaporizing brake pads a place to go under hard braking. Slotted rotors resist cracking, unlike drilled rotors which have the tendency to crack in between the holes. The vented Fastbrake rotors cool better than stock, have better initial bite due to the slotting and are larger for more thermal mass and better mechanical efficiency.