Guys, I got correct part numbers for the calipers here. I referenced ZZPerformance, Racing Brake, GM's site, and various LS1, CTS, Corvette, S14, GTR, etc forums to gather this info. I hope there are no typos here.
Gen 2 CTS-V 6 Piston
Yellow:
GM P/N 20982719 or AC Delco P/N 172-2521
GM P/N 20982734 or AC Delco P/N 172-2522
Silver:
GM P/N 25912477 or AC Delco P/N 172-2487
GM P/N 25912967 or AC Delco P/N 172-2488
Red:
GM P/N 22885106 or AC Delco P/N 172-2595
GM P/N 22885108 or AC Delco P/N 172-2596
ATS-V
Gold:
GM P/N 23121834 or AC Delco P/N 172-2685
GM P/N 23121835 or AC Delco P/N 172-2686
Red:
GM P/N 23121832 or AC Delco P/N 172-2683
GM P/N 23121833 or AC Delco P/N 172-2684
Silver:
GM P/N 23121830 or AC Delco P/N 172-2681
GM P/N 23121831 or AC Delco P/N 172-2682
Camaro 6G SS 1LE 6 Piston
Red:
GM P/N 84063672 or AC Delco P/N 172-2741
GM P/N 84063673 or AC Delco P/N 172-2742
Camaro 5G ZL1
Black:
GM P/N 20944530 or AC Delco P/N 172-2537
GM P/N 20944518 or AC Delco P/N 172-2538
2015-2019 Corvette Z06 - has dimpled pistons for supposedly better cooling
Red:
GM P/N 23242497 or AC Delco P/N 172-2669
GM P/N 23242498 or AC Delco P/N 172-2670
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Caliper bolts from the CTS-V are M14 x 2 and 56mm long. Stock M3 caliper bolts are M12 x 1.75 and 45mm long. So... You'll have to either:
1. Easiest method. Drill out the pilot holes with a 14mm or 9/16" drill bit. Then, purchase the GM 56mm long M14 x 2 bolt and use washers to eat up approximately 12mm of the bolt to prevent it from protruding too far. GM also has 45mm long M14 x 2 bolts made for the Camaro, or eBay has them available as well. If you do this and ever decide to go back to stock, then you just need to shim the widened pilot holes with a 14mm OD 1mm thick aluminum pipe cut into a shim (ID = 12mm to fit the stock caliper bolt). Amazon sells the aluminum pipe for $10.
2. Keep things stock method. Get the caliper threads tapped with a 24mm long M12 x 1.75 time-sert. These are hardened steel threads that are commonly used to repair stripped aluminum threads in engine blocks and such. Rethreading the calipers to fit M12 x 1.75 bolts should be easy. You find a machine shop or auto shop to tap the existing calipers with the time-sert insert, and that's it. You can buy the time-sert kit and do it yourself as well. It's about $120 for the kit, and $25 for the 24mm long inserts. Many places to buy time-sert kits. Just be aware that you have to cut new threads into the calipers if you go this route.
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Brake pads. Stock Brembo pads are P/N 171-1040, and at this time are about $225. I hear they're decent, but a little dusty. My research in other forums revealed users tracking them with good results, but they'll wear out quickly. Otherwise, just grab your preferred street or track pad made for these GM calipers (which will likely match many other 6 pot Brembos, but I have not confirmed that).
You will need to purchase the pad pin kit for the above calipers P/N 18K2108X
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Rotors. This is where we are today with the Girodisc group buy. Hopefully, they pull through with the currently committed people. That way we can simply purchase off the shelf parts from them. 370mm x 34mm rotor rings for the CTS-V, Corvette, Camaro are already available through Girodisc, so having the hats made is the last step.
Alternatively, you can buy the Racing Brakes kit that includes all you need to install this BBK except the calipers (see above for your choice of color and logo).
RB BBK (370x34) for Tesla M3 Retrofit to Cadillac CTSV V2 or Camaro G5 ZL1 6 Pot Calipers
Many of us much prefer to go with Girodisc, though.
Lastly, as someone already did for the previous gen Model S, you can design your own hat and mate it to the correct Brembo rotor ring. You simply need to have access to your own machine shop and design studio to do this.
DIY...Big Brake Kit for Under 2k