Bigger tires require better brakes. Radically bigger tires often require oversized disc-brake rotors and brake pads designed for repeated hard stops. If you want your truck to stop quickly and in a reliable fashion, you have to install brake components that are bigger and dissipate heat better than OE rotors. Friction from repeated braking causes heat.
If that heat is not efficiently dissipated, it will build up and result in brake fade, making stopping distances longer and requiring greater pedal pressure. The easiest way to prevent this heat buildup is to make the brake rotors larger. The extra metal and wider venting fins of a larger, thicker rotor keep heat buildup under control. The added size also gives the brakes a leverage advantage over the tire compared with stock; just as it is easier to loosen a nut by putting a length of pipe on the wrench, so it is easier to stop a spinning disc rotor when the caliper is further away from the rotor's center.
We've been working with Stillen for many years and know that the company puts out high-quality products. We let Stillen know what we were doing with our F-150, and the brake pros suggested the AP Racing system. The AP kit features six-piston calipers and two-piece, 14-inch-diameter curved vane rotors. The cooling vanes direct air through the centers and help dissipate heat. The rotors are cross-drilled and slotted to allow gasses that build up between the rotor and the pad to escape.
To prevent stress cracking, the cast-iron discs are mounted on aluminum hats. The Stillen/AP Racing calipers are made of lightweight aluminum alloy and use three pairs of pistons. Trailing-edge pistons are slightly larger in diameter than the leading pistons to compensate for end load and protect the pads from uneven wear.
The system is a true bolt-on application, but it requires an 18-inch-diameter wheel with a minimum pad-height clearance of 1.420 inches and inner-diameter clearance of 16 inches. A diagram of the calipers and rotors can be found on Stillen's Web site. Be sure to check your truck's wheels or the new wheels you're ordering before attempting the Stillen Brake Pros upgrade.
Better Brake Lines
Not only do braided brake lines offer extra protection against damage, they also resist expansion when the fluid within them is under pressure. Standard OE rubber lines expand under pressure resulting in a spongy feel. Braided-steel brake lines incorporate a PTFE inner liner covered with a stainless-steel outer braid. In the case of the Stillen/AP brake lines, they are DOT-approved and pressure tested to 3,000 psi.
Bed Them Right
Once you have the Stillen/AP Racing brakes (or any new set of brakes) on the truck, you'll want to follow the following steps to bed the brake pads and rotors. Properly bedding the new brake components will improve the rotors' resistance to heat cracking and warping. For the first 10 miles, brake lightly from 50 mph down to 0; do this five times. For the next 100 miles, increase the braking pressure, but try and avoid full (panic) stops from 70 mph and above.
At all times during this procedure, avoid sitting with your foot on the pedal (as at a traffic light). Place the transmission in Park if you're stopped; doing so will keep the pads from creating a localized hot spot on the rotor, which creates a high spot on the rotor's face, resulting in a vibration or a pulsating pedal.
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 Here is what the stock brakes...  Here is what the stock brakes look like -- not very impressive. Once the engine is built and large-diameter tires are added, the OE brakes' performance might not be powerful enough. After the truck was safely secured on the rack, the front tires came off to access the brake system. |
 The two caliper mounting bolts...  The two caliper mounting bolts were removed, and the caliper was removed; the brake line doesn't have to be removed yet, so the caliper was put out of the way. |
 Once the dust cover, the cotter...  Once the dust cover, the cotter pin, the castle nut, and the outer wheel bearing were removed, the rotor was removed. If you reinstall the castle nut and washer before you remove the rotor, it will pull the seal out as it's removed, saving some time. |
 The backing plate is also...  The backing plate is also removed; it's held on with a few bolts. |
 Here is a side-by-side view...  Here is a side-by-side view of the Stillen and the OE rotors; you can see how much bigger the two-piece modular AP Racing discs are. |
 This truck is relatively new,...  This truck is relatively new, and the wheel bearings and seals are in great shape, so after a fresh packing of grease, the bearings and seals were installed into the new hub. |
 The hub slips right onto the...  The hub slips right onto the stock spindle (axle stub), as would the stock rotor. Then the outer wheel bearing, the castle nut, and the new cotter pin and dust seal went back on according to factory specs. |
 The caliper mount is attached...  The caliper mount is attached to the steering knuckle using the same holes as the OE caliper and using the OE fasteners. |
 Now, slide the AP rotor over...  Now, slide the AP rotor over the studs. The AP Racing 14-inch disc rotors have directionally curved vanes vented for maximum cooling and are cross-drilled and slotted for aggressive pad bite and proper out-gassing. |
 The pads were installed after...  The pads were installed after the metal backing plates were sprayed with anti-squeak coating |
 Here is the caliper fresh...  Here is the caliper fresh out of the box with its new brake line and hardware |
 The calipers were slid onto...  The calipers were slid onto the mounting studs and were tightened to 52 lb-ft of torque. The calipers use conventional seals in conjunction with a dirt seal and are finished with a black PTFE paint coating that is impervious to normal brake fluids and high brake temperatures. |
 Next, the stock brake lines...  Next, the stock brake lines are removed. The new braided stainless-steel lines are installed and routed through the same path as the stock rubber lines. Once the new brake lines were installed, we turned the steering from lock to lock to make sure the lines aren't pulled or pinched. |
 Here is a shot of what the...  Here is a shot of what the Stillen/AP system looks like when fully installed. |
 The master cylinder was topped...  The master cylinder was topped off with fresh DOT 5 brake fluid. |
 The brake system was thoroughly...  The brake system was thoroughly bled; keep an eye on the master cylinder because the calipers are shipped dry, and it takes quite a bit of fluid to completely fill them. Lightly tapping the caliper body with a brass or plastic hammer will help move the small bubbles in the fluid to the top. |
 With the system bled, the...  With the system bled, the wheel went back on. You can see the new brakes fill the area behind the wheel nicely. After a final inspection, drive the truck at a moderate speed, and make several moderate-speed stops in order to properly "bed" the brakes. To finish off the bedding procedure, check the sidebar at the end of this story. Now you're all set to experience way-better braking. |