Sometimes the point of a particular exercise isn't as clear as one might think. Take the example of installing a big-brake kit onto a new C7 Corvette. Many may think that the main purpose is to shorten the distance needed to bring the car to a halt, but that’s not really the main point at all. Let’s face it, new cars stop pretty damn good already. With ABS and modern components, GM put a lot of thought into these systems to make sure the car can “panic stop” in short order.
So then, what’s the point of spending big bucks upgrading a brake system? The answer is repeatability. Sure, the new brake system might shave a few feet off the stopping distance, but the big payoff is the new brakes will pull off repeated heavy braking over and over while better resisting heat-induced brake fade. GM didn’t set out to offer race quality brakes, even on something as capable as the new Stingray. As such, the factory parts tend to degrade in performance when subjected to heavy punishment. This is where aftermarket companies like Wilwood come into the equation.
Brakes work by converting forward momentum into heat energy and this heat needs to be properly controlled. This heat needs to be insulated from the brake fluid and, most importantly, dissipated quickly from the rotors. This is where the larger mass and staggered-vane arrangement of an aftermarket rotor really pays off. More mass means the rotor can hold more heat in addition to being stronger while the design of the vanes helps move air through the rotor more efficiently than the less expensive to produce factory rotors. Today, drilled-holes in the rotors are more for looks, but slots still play a role by providing smoother pad engagement and improving the thermal balance across the rotor. A larger rotor diameter also moves the caliper away from the hub thus increasing its leverage.
Now one might think all this weight might hurt other performance areas, and to some degree it does, but the benefits outweigh the downsides. Wilwood helps keep the overall weight down by employing a two-piece rotor with a center section, called a hat, composed of lightweight aluminum. Still, a bigger iron rotor will always be heavier because physics says it needs to be. GM claims that the C7 rotors are a “faux” two-piece deal, even though they are one-piece. We get what they are saying in terms of the rotor design, but the truth is in a real two-piece rotor the hat is aluminum. More than just being lighter, it also dissipates heat better under hard use and is less likely to transmit heat into the wheel bearings. You want mass in the rotor, not the hat. We weighed both (Wilwood and Z51 GM) and found the weights to be nearly identical. Since we know the center of the Wilwood (aluminum hat) is lighter that means there’s more mass in the rotor itself. It’s also a litter bigger (14.25 vs 13.6) than the Z51 rotor and a lot bigger than the base model rotors that measure out at 12.6 inches. And, as any physics student can tell you, the farther the caliper gets from the center of the hub the greater leverage effect it has.
The caliper is another area where braking performance can be gained. The factory front calipers on our C7 are four-piston pieces made by Brembo. Now, Brembo certainly makes good brakes, but what’s on the C7, even the Z51-equipped Stingrays, are high-performance street calipers. They are fairly heavy, have dust boots, aluminum pistons, and they’re painted. All things that are fine for the street, and very light track duty, but elements that won’t resist heat very well when pushed. In short, they work great on the street and can panic stop you in a sub-100-foot distance from 60 mph, but after repeated hard stops, as seen at the track, the boots start melting, the paint turns odd shades, and effectiveness dwindles.
While the factory brakes mount directly to the spindle, the aftermarket switches over to a radial-mount fixed caliper. The revised mounting simplifies the installation and gives two planes of adjustment so that the caliper is precisely aligned over the rotor. The caliper itself is stronger than the OE unit to better resist flexing, which degrades brake performance. The pistons are made of stainless steel, as opposed to aluminum, to better insulate the brake fluid from the massive amounts of heat generated. Piston area, pad volume, and a host of other aspects are optimized for doing one thing: quickly bleeding off speed over and over again. Add in brake fluid that’s designed to operate at higher temperatures along with the right brake pads and the end result is a brake system that will be going strong long after the factory parts would have given up the struggle. Oh, and they look cool, which is always a nice side benefit.
1. The C7 comes with very nice brakes, but the engineers at Wilwood thought they could improve on the braking performance a bit. The first step was to unbolt the OE caliber, leaving the brake line attached, and set it on top of the spindle. This way we didn’t have to worry about brake fluid leaking everywhere while we were installing the rest of the parts.
2. Next up was installing the bracket for the radial-mount caliper. Per the instructions, we initially installed two 0.029-inch thick shims on each of the two bolts between the bracket and Corvette upright.
3. We then temporarily attached the bracket, making sure it was square to, and properly seated against, the upright bosses. Later, after confirming caliper alignment, we went back and added Loctite 271 before torquing the two bolts down to 77 ft-lb.
4. It was then time to mate the hats to the rotors. The two parts were aligned and we hand inserted the 12-point fasteners, each with a dab of red Loctite 271, in the holes. Using a star pattern, we tightened each to 155 in-lb. If you want extra security you can safety wire the fasteners using 0.032-inch stainless wire.
5. The 14.25-inch diameter Spec 37 GT slotted and staggered-vane rotor (left), sitting next to the stock OE rotor, is 1.25-inches thick and all that mass is what you need in a performance rotor. The SRP version of this kit comes with drilled, slotted, and E-coated rotors, but it’s not recommended for heavy track use. We weighed both and, even with the aluminum hat, the Wilwood assembly was a couple of ounces heavier. This is a good thing since mass in the rotor is what you want.
6. This kit also utilizes Wilwood’s new AERO6 six-piston caliper. They are 15-percent more rigid than their predecessors while weighing 0.5 pounds less (almost 4 pounds lighter than the OE Z51 calipers). A significant achievement considering how much effort went into their previous caliper. Notice the lack of a bridge bolt. This is one aspect that contributed to the added stiffness. The calipers come in your choice of black, red, or Quick-Silver nickel. You can also add Thermlock pistons if you plan on heavy track use.
7. The OE rubber brake lines weren’t compatible with the Wilwood calipers so we installed these fittings (included in the kit) into the 1/8-27 NPT caliper inlets.
8. Here you can see the OE brake pad to the far left, the Wilwood BP-20 (street/track) Smart Pad in the center, and a rear pad to the far right. The front and rear Wilwood kits use the same size/type pad. The SRP kit includes Wilwood’s BP-10 street pad.
9. The hardest part of this install was removing this OE bracket that held the brake line. It just required patience and some contortion to remove.
10. It also needed to be modified by opening up the hole to 0.500-inch diameter using a hand drill.
11. We then slid the registration adapter over the hub with the small side facing outward.
12. This allowed us to install the rotor/hat assembly and temporarily hold it in place with some lug nuts.
13. After lubricating the caliper mounting studs with some lightweight oil, we initially placed two 0.030-inch thick shims on each stud. The caliper was then mounted (keeping in mind there is a right and left caliper) without pads to check alignment. We made sure the rotor was centered in the caliper, which it was. If it wasn’t we would have added or subtracted bracket shims as needed. Make sure you always use the same amount of shims on each mounting bolt.
14. The caliper was aligned properly so we installed the BP-20 pads by popping out the retaining clips and sliding out the pins. We then slid in the pads and reinstalled the pins and clips. With that done we could slide the caliper onto the radial mount studs. At this time we checked to make sure the top the brake pad was flush with the outside diameter of the rotor. It was, but if it wasn’t we would have pulled the caliper and added or subtracted shims to change the caliper height. The caliper nuts were then torqued to 47 ft-lb.
15. With the caliper in place we removed the OE caliper and installed our new DOT-approved stainless brake line. We also made sure the line wouldn’t rub any components.
16. It was then time to move to the rear of the C7. Like the Wilwood front kit, the rear system is offered in two flavors: SRP for the street and GT for the street and track. We’re not going to bore you with how the remove the rear caliper and rotor.
17. Just like the front, we first installed the registration adapter over the hub.
18. Installing the caliper mounting bracket was just like the front except we used one 0.033-inch thick shim between the bracket and the upright. The bolts were just snugged until we confirmed caliper alignment. Later they will be coated in Loctite 271 and torqued to 77 ft-lb.
19. The rear rotor in either the SRP or GT kit will measure out at 14.25 inches in diameter and 1.10 inches in thickness. They feature the same super-efficient, staggered vane design for optimal cooling.
20. The caliper alignment procedures used on the front system were then repeated for the rear. With everything checked we installed the BP-20 Smart Pads and slid the four-piston AERO6 caliper into place.
21. Like the fronts, we had to use the new braided stainless lines (PN 220-9101) in the kit and ditch the rubber OE pieces.
22. Per the instructions we modified the plastic brake ducting to allow clearance for the new braided brake line. Here you can see the before…
23. …and after.
24. Here you can see how the line will route through the modified brake duct panel.
25. And just like that we were done with the installation and could then bleed the system using Wilwood’s high-temp fluid.
26. We knew the Forgeline wheels would clear the bigger brakes, but we wanted to make sure stock rollers would be good to go as well. The new brakes look killer behind the wheels and we can’t wait to bed them in and hit the track!