I converted my 04 front brakes to 05 OEM rotors and calipers. From all I can tell, beertestr was first to make the 04 to 05 front conversion. His write-up convinced me the project was very doable and that the only way to match or beat the quality and performance of the OEM 05 GTO front brake package, which uses the new C6 Corvette brake calipers, was to go with an expensive 4s and 6-piston set-up like StopTech’s or Wilwood’s. Baer makes a reasonably priced upgrade kit for the GTO but uses a C5 caliper, which is not as stiff as the C6. Also, if you have to replace the Baer rotors they are more expensive than OEM, and … don’t get their drilled rotors as several GTO owners have had theirs crack! You have been forewarned! JHP, an Australian-based company, has brake upgrades with front rotors that are 330mm vs 320mm for the 05 (13.0 vs 12.6 inches). I believe that the JHP calipers are from the C5 vs 05 GTO calipers that are from the C6 which are stiffer. I'm not sure you will see the extra .2-inch difference in radius, even if you track your GTO. You also have to consider shipping charges from down under plus there is duty when they get here (may be as high as 20%). I choose to stay with the 05 OEM components and obtained them from mid-West salvage yards that had collected some of the 35 or so 05 GTOs that were damaged in the April 2005 train wreak in Iowa.
All you need for this OEM conversion are calipers, rotors, and brake lines plus a short length of Ĺ-inch steel tubing. You can search for used 05 GTO parts via the Internet via at http://www.car-part.com
. I obtained all my components from the salvage yard for less than $300 including shipping. If you go through a salvage yard, make sure you ask for brake lines and pads. The brake lines are about $15 each. Also, the brake lines have a plastic piece, like a doughnut in the middle of the line, which holds the brake line to the strut. You have to rotate the line about 90 degrees to slide it in and out of its metal keeper that is welded to the strut. The salvage yard needs to know this or they will break off some of the plastic tabs. My brake lines were like this but still worked and held in the keeper. You can see the piece I'm referring to just above the "before" 04 rotor attached to the strut.
If you decide to purchase these parts new, here are the component costs if you buy them from a place like http://www.GMPartsDirect.com
∑ 2 caliper assemblies $235/side. GM part nos. 92175206 for the right and 92175207 for the left. This includes the calipers and brackets. You can not buy the brackets separately.
∑ 2 front rotors $112 each. GM part no. 92161569.
∑ 2 brake hoses $69/side. Keep in mind they are side-specific and the banjo fittings are clocked at 90 degrees. If you are going to buy new brake lines, you should consider stainless steel braided aftermarket, which offer more performance and are more affordable. http://www.StopTech.com
has the pair for $99. I did not have the GM part nos. at the time I published this.
∑ 1 set of pads - pick your favorite. Just don’t reuse your 04 OEM pads! They are much diminished in size from the OEM 05 brake pads, which still are slightly smaller in surface area to the C5’s (all three use the same backing plate). Keep in mind that the caliper is the same as the Corvette C6, which takes the same pad as the C5. If you can't find the GTO specific pad you like, shop for Vette pads, GM part no. is 88909667. The cost can be anywhere from $50 to $150.
What does this buy you? An 05 rotors that is much beefier than the 04 and a great caliper!! OEM 05 rotors are 1 inch larger in diameter and .2 inches thicker making them about 5 pounds heavier than the 04 rotors (22 vs 27 pounds). The extra thickness is all toward the outside of the vehicle and allowed the 05 rotors to stand upright on their own. The internal venting structure is different as you can see in the picture. The 04 rotors had vent supports that ran as a single column radial from the center out. I believe the 05 design ensures more even thermal expansion during hard braking so the rotor does not develop high spots when hot. The 05 calipers are much more massive than the 04. I was shocked when I first saw their size! The 2-D picture just does not relate this. The 05 calipers are almost 1.5 inches wider and its all structure because the pistons (slave cylinders) are the same size on both the 04 and 05. The 05 calipers actually fit in the 04 brackets (logical because they both can use the same C5 brake pads). However, I did not experiment with using the 05 calipers on the 04 rotors because with the 04’s thinner rotors and the 05 caliper’s extra total width, it looked like it was mounted too far inboard and might interfere with the suspension during turns.
The conversion took me four hours to complete including initial set-up and all clean-up. This length of time seemed a bit long but I had a rotor that refused to come off even with a puller (puller plus banging finally got it), I had my son doing some of the work for his experience, and I did take time to take pictures. It is really a simple bolt off the old and bolt on the new type of mod. BTW, my 12mm bracket bolts took a lot more than 100 foot-pounds of force to loosen them. I reused my C5 pads I had installed in my 04 the first month I had it.
Here are the steps for this conversion. They are expanded from beertester’s original instructions. The difference between changing out your front pads when they are worn and this upgrade is 3 bolts per side. These instructions assume you already have the car raised and the wheels off.
1 – Remove the caliper from its bracket like you would to change out the pads. Don’t let the caliper hang by the brake hose so suspend it with string, a bungee cord, or coat hanger. By keeping the old caliper up out of the way until you are ready to install the new brake hoses, you will save yourself some mess. You can remove the brake hose from the strut by twisting it half a turn and sliding it out of its bracket.
2 – Remove the two 12mm bolts holding the bracket to the knuckle and remove the bracket. You will need to reuse the 12mm bolts to install the 05 caliper brackets. Refer to the end of this section for instructions on how to add the 1mm shims to make them compatible with the 14mm bolt holes in the 05 bracket.
3 - Remove the 04 rotor. If your car saw any winter driving, the rotor may be rusted on to the hub-flange of the wheel-bearing unit. If you plan to keep your 04 components for reuse, use a hammer and a block of wood to beat the rotor off the hub. Hit the wood, not the rotor so you don’t deform the machined rotor surface. It may take a few minutes of pounding on the backside of the rotor to get it off the hub.
4 – Remove the dust shield. If you plan on ever putting the car back to stock, you should remove the brake dust shields nicely. This means unhooking the ABS line (easy connector) and unbolting the bearing/hub unit from the knuckle, and drilling out the rivets that are holding the shield on the knuckle. I don’t think the shields are worth saving and quickly disposed of them by cutting the rivets off with a chisel. This will save you about 15 minutes/side and provides a small weight reduction to offset the increased weight of the beefier 05 rotors.
5 - Install the new rotor. Marvel in how much beefier it is. Consider using Squeal Medic for corrosion protection as described in the General Tips section. You may want to use a lug nut hand-tightened to keep the rotor aligned with the hub until you are ready to re-install the wheel.
6 - Install the 05 caliper bracket assembly on the knuckle. As stated in step 2, the 05's use a 14 mm bolt, but the 04's use a 12 mm bolt. After you have installed the 1mm sleeves on your 04 bolts (as described at the end of this section), tighten to 100 lbs/ft. I’d recommend using some blue Loctite on the threads before you re-install the bolts back onto the knuckle.
7 – Insert the brake pads and install the red 05 GTO caliper (with its brake line already attached) onto the bracket and secure. Insert the brake line into the keeper on the strut.
8 - Now is the time to crack open the old brake line at the firewall. First, put a drain pan under the brake line on the fender/wheelwell. Loosen the bolt holding the bracket to the fender so it can be removed later by hand, and then remove the flexible hose from the solid line. Since you have the new brake line already to connect, you should experience minimal fluid loss. Make sure you don’t but a twist in the line when you bolt the brake hose bracket to the fender.
9 – Set-up your bleed hose and reservoir. Crack the bleeder valve on the brake caliper and let it gravity bleed while you are working on the other side. This speeds up the bleed process a lot.
10 - Repeat for the other side and gravity bleed them also.
11 – If the gravity bleed did not give you a firm pedal, get your wife, roommate, girl friend, or idle child to help you bleed the brakes. It is not uncommon to have to bleed the GTO brake lines two or three times to get all the air out and have the pedal feel firm. But once you do, the pedal feel is awesome compared to the 04 brakes. You will love them. The add stiffness of the C6 caliper is very noticeable.
12 – Drop the car on the ground and burnish the pads and rotors. If you need the technical details on how to do this, follow the recommendations from StopTech at http://www.stoptech.com/tech_info/wp...contents.shtml
I’ve included a before and after shot. For daily around town driving, I do not notice a difference in stopping distance. High-speed haul-downs on the track were signficanlty improved. The brake pedal is now much firmer and I really notice it when applying maximum pressure. I still have not gotten used to the new firmness even after several months of driving – its like a pleasant surprise every time I touch the brake pedal. I originally was going to get just the calipers and use aftermarket slotted rotors and stainless steel brake lines. The improvement in brake firmness was so dramatic with the 05 calipers, I've put off upgrading to stainless steel lines for a while. The next most important upgrade I would recommend is getting the vented 05 rear rotors and modifying the dust shields on the rear to allow air to get into the vent channel. This is beneficial for all GTO year models and is covered in the companion thread discussing rear brake enhancements.