2005 Pontiac GTO Brake Upgrade - Speed Slayer

The caliper was then slid on and its mounting bolts torqued to a Wilwood-specified 47 lb-ft. These nuts do not need threadlocker as they are locknuts (kudos to Wilwood for this). Note also that Wilwood said to install the caliper with the bleed screws facing up, but since these are four-piston units, they will have two on the top and two on the bottom no matter what!

The brake pads slid in place on either side of the rotor, and the retainer clip was then installed over them. These "BP series" brake pads are said to provide response and temperature range characteristics that are matched to Wilwood's front brake kits.

One last order of business: brake line adaptation. We used the aforementioned Flexline kit to adapt the factory hard line to the new caliper. It includes an adapter to go from the factory line to AN (no reflaring required), then a braided AN line, and finally a 90-degree AN-to-pipe adapter (shown being installed here). This 90-degree fitting installs into the caliper, noting that pipe thread sealant must be used at this connection (and nowhere else). Secure it in place with an 11mm or 7/16 open end, but not too tightly as you will remember you are threading into aluminum. In terms of clocking, straight up should work fine, though ours ended up having to point a bit more toward the back of the car to fully tighten. If you prefer, this fitting can also be installed before setting the caliper in place.

The Wilwood instructions suggest fabricating a bracket to hold the new brake line, but we opted to just gently bend the factory hard line and route it behind the shock, keeping it well away from wheel interference. The Wilwood braided line was then attached to the factory line using 7/16, 11/16, and 10mm line wrenches. No pipe thread sealant on these; they are all flared! The above steps were repeated for the other side of the vehicle with similar shimming and alignment procedures; the number of shims used on your vehicle may vary from ours, and will also likely vary side-to-side. The rear brakes were then bled, the wheels reinstalled, and it was time to move on to the front of the car!

Wilwood's PN 140-8753 Superlite 6 Big Brake Front Hat Kit carries an MSRP of $1,867.35. Its main features are Billet Superlite six-piston calipers and 13-inch GT directional vane rotors, but drilled and 14-inch rotor versions are also available. As with the rear brakes, it's best to also pick up one of Wilwood's Flexline kits to adapt to the stock brake lines (PN 220-8755, $88.83).

After jacking up the front of the GTO, a wheel was removed (here, the driver side). The stock front calipers are PBR two-piston units working on 12.6-inch rotors. Again, they are fairly decent units from the factory, but whoever said you can't make a good thing better?

Before the caliper can be removed, one must disconnect the OEM rubber brake hose from the hard line using a 10mm line wrench. We removed the rubber hose assembly from the shock by turning the black plastic grommet assembly 90 degrees and pulling it out of the back (shown in right hand). We also unbolted the entire sliver metal bracket securing the end of the hose to the body (shown in left hand, already unbolted).

We then removed the stock brake caliper mounting bracket and caliper assembly as one piece; two 21mm bolts were all it took. Turning the wheel can assist access to these.

The factory rotor may be stuck on pretty good. If so, use some penetrant on the rotor hat about the wheel studs and exposed central area of the hub.