2005 Pontiac GTO Brake Upgrade - Speed Slayer

The stock rotor-which is only about 11 inches in diameter-just slips off the hub, revealing the GTO's e-brake system (which uses the inside of the rotor hat like a brake drum). Cars with a lot of miles on them might have a bit more corrosion between the rotor hat and the hub, so they may require a bit more effort for rotor removal.

The most difficult and time-consuming part of the rear brake installation is that the factory dust shield must be cut to make room for the new rotor and caliper. Though detailed specifications are provided by Wilwood on exact trimming diameter, they basically translate to annihilating the shield completely. A reciprocating saw was our tool of choice, and since it's hard to make a turn while cutting with such a blade, we cut in sections and then finished off the near-circle with a grinding wheel....

...Be especially careful of the parking brake cable behind the lower portion of the dust shield while cutting. Once you're happy with the rough shape, a smaller grinding device (such as a die grinder) will be needed for final smoothing and deburring all around. When you're done, vacuum up all the metal shavings and shoot the cut/ground edge with a bit of black paint to prevent corrosion.

It was time to begin a full "dry run" of the installation. The CNC-machined aluminum caliper mounting bracket bolts in place using the stock bolts along with Wilwood's provided shims underneath (one thin shim per bolt for now). We oriented the bracket so that the flat side faced away from the rotor. Note: Wilwood said to use the factory washers under these bolt heads, but our bolts didn't have any. Again, since this is a test fit, nothing is being final-tightened yet.

The new rotor was slid on and held by a couple of lugs to keep it flat against the hub. The caliper then slipped onto the mounting bracket with the appropriate shims on the mounting bracket's studs (these shims space the caliper radially from the rotor, while the previously installed shims change its spacing side-to-side). We then looked to see if the rotor was centered between both sides of the caliper. It wasn't, so we added shims behind the caliper mounting bracket. After some trial-and-error in adding shims, we were happy with the way the side-to-side spacing looked, so it was time to adjust the caliper's radial spacing off of the mounting bracket. With the Wilwood-specified amount of shims in place, we found that the caliper physically contacted the rotor, so two more shims were added to each mounting stud. The caliper was then temporarily bolted in place using the provided 7/16-inch nuts and washers on each stud.

The brake pads were then temporarily installed. (By the way, Wilwood uses a cool quick-change pad system for the rear brakes that just involves popping a retainer clip [gold] in and out.) The objective here is to ensure that the edges of the pads line up with the outer edge of the rotor, which in our case they almost did; though just about exactly even with the edge of the rotor, we opted to try and remove one shim from each caliper mounting stud just to be safe. After all, that last tiny bit of brake pad that might be hanging off the edge of the rotor could affect braking performance. However, going to only one shim causes the caliper to be way too close to the rotor (almost invisible clearance),so we had to stick with two.

The wheel was then bolted on, and with the car in neutral, spun to ensure no binding or scraping of any parts. It turned just fine, and we didn't hear anything abnormal. (Attempts were made to spin the rotor without the wheel on, but it would seem the GTO's posi unit prevents the rotor from turning easily without the larger diameter of the wheel to help add turning torque. Regardless, it is better to have the wheel in place now, as it ensures the rotor is securely held against the hub, yielding the best representation of what the rotating clearances will be after final installation.)

It was then time to disassemble everything. As the system comes apart, one must note the number and location of all the shims so that this can be duplicated during final assembly. The caliper bracket mounting bolts were first installed using red threadlocker. After ensuring proper placement of the gold shims (shown), these bolts were inserted into the stock locations on the vehicle and torqued to factory spec.

The rotor was popped on and wiped with a paper towel soaked in brake parts cleaner; this helps ensure proper pad seating and squeak-free operation since it removes any debris and fluids from the rotor. A couple of wheel lugs were then installed to hold the rotor squarely in place during the rest of the installation (otherwise, the caliper and pads may not want to go on).