Installing C5 brakes on my 1970 Corvette
Let me start this off by saying that the C3 Corvette brakes are actually a really good design. Afterall, how many cars do you know that came from the factory in 1970 with 4-piston calipers on all four wheels?
Now with that being said, there is always room for improvement. Such as lighter, more efficient calipers, larger rotors, etc. So my search for new brakes began.
I checked with all the major manufaturers such as Baer, Willwood and Stainless Steel Brakes. I couldn't find anyone to offer larger rotors (other than custom one off setups that were in the thousands of dollars.) I was then drawn to more modern GM products specifically Camaros, C4s and C5s. After a lot of help from the Corvetteforum with getting various dimensions, I determined the C5 setup to be the best cost/benefit solution. So where did I turn? Ebay of course. Afterall, if it's not on ebay, you don't really need it! I saw several sets of calipers and rotors sell for around $400. Not bad at all. I kept looking and a set of drilled and slotted rotors along with the red Z06 calipers were put up for only $250. SOLD!! Here is a pic of the add on ebay.
The new rotors are 12.8 x 1.25" fronts and 12 x 1.0" rears. These require a few minor mods to get them to fit. First, the C3 hubs are rather large measuring in around 6.25" in diameter. The rotors are machined with 6.1" of hub clearance.
So now I have two choices. Modify the car to fit the brakes or modify the brakes to fit the car. Well I ended up doing both. The front hubs are easily removable and I had them turned on a lathe to remove 0.25" in diameter. This gives me 0.1" to play with. Because of the prior measurements, I knew that the center bore of the rotor was just the same as the hub. Before I removed the old rotor I did a test fit of this with the new rotor backwards and it fit great, very snug. Once the old rotor was off, I ran into another problem. I did not notice that the stock rotors sat on a little raised lip. That would have to go as well. Since I was already at the machine shop, I had them press out the old and in some new wheel bearings. You can see the machined spots in the pic.
Here is a pic of the modified hub and new front rotor trial fit. Everything fits great now.
For the rear, there is actually about 7" of hub clearance. The only problem there is the raised lip where the part #'s are stamped. The hub mating surface is only machined to 6.1" like the fronts. Now I wasn't about to take off the rear hubs and deal with a trailing arm rebuild right now, so I had the machined mounting surface of the rotor enlarged by 0.25". Now the rear rotors fit great.
Now that the rotors were on the car it was time to move on to the caliper brackets.
On the front, the stock brackets are made from 1/4" stamped steel. These mounted to the front of the spindle above the axle and to the back of the steering arm in front of the axle. I chose 1/2" aluminum for the main brackets with aluminum spacers to center the caliper over the rotor. I used the old brackets as a template and fabbed the part that fits to the spindle. I had to "sand" away at the lower mounting point to preserve the 1/4" thickness to get the bracket to sit flat. Once the partially made bracket was on the car, I was able to mock up the caliper and figure out where to drill the two mounting holes. The bracket was rough cut with a sawzall then gently massaged into shape with an angle grinder. After about 3,000,000 hours of labor and several sanding discs, this is what you get. The dogbone shaped spacer was used for fabrication and was scrapped for two smaller ones that were turned on a lathe.
On the front, the stock brackets are made from 1/4" stamped steel. These mounted to the front of the spindle above the axle and to the back of the steering arm in front of the axle. I chose 1/2" aluminum for the main brackets with aluminum spacers to center the caliper over the rotor. I used the old brackets as a template and fabbed the part that fits to the spindle. I had to "sand" away at the lower mounting point to preserve the 1/4" thickness to get the bracket to sit flat. Once the partially made bracket was on the car, I was able to mock up the caliper and figure out where to drill the two mounting holes. The bracket was rough cut with a sawzall then gently massaged into shape with an angle grinder. After about 3,000,000 hours of labor and several sanding discs, this is what you get. The dogbone shaped spacer was used for fabrication and was scrapped for two smaller ones that were turned on a lathe.
Here is the caliper mounted on the bracket.
The front brakelines are 3/16" braided lines that I had made at a local shop with a standard 3/8-24 brake fitting on one end and a 10mm banjo fitting on the other.
Here is the completed front assembly.
The rear brackets were a little different in design. Since the rear caliper bracket cannot be removed without disassembling the bearings, I had to leave it in place. This meant making an adapter for the old bracket to make it fit the new caliper.
I again chose 1/2" aluminum with spacers for the brackets. The stock caliper mounts to the backside of the stock bracket whereas the C5 caliper mounts to the front of the bracket. The front side is slightly angled, so the adapter would have to go on the back. Unfortunately using this method to mount the caliper meant that it would have to be on top of the trailing arm to get it to fit.
The rear brackets only took about 2,000,000 hours to create with the sawzall and the angle grinder. Here is a shot of the right rear on the car. Also, the bracket on the top of the trailing arm and the dust shield had to be cut for clearance. Notice how big those caliper bolts are in comparison the the stock ones.
Here is the finished left rear setup. You can see the 3/16 braided lines. These were also custom made with a -03 AN fitting on one end and a 7/16 brake fitting on the other. The hard line is ~5" long stainless with a male -03 AN on one end and a 10mm banjo on the other. I know it looks close, but the rubber up stop on the frame actually clears the caliper.
New wheels for new brakes. The wheels are Boyd Coddington Nemesis 17x8 with 4" backspacing and Kumho Ecsta MX tires 245/45/17. When I ordered the wheels, I specified 1970 corvette. I didn't even think to tell them that I was using larger brakes. The spokes curve in as they get towards the outer edge of the rim. I ended up using 5/16" spacers to get the clearance for the calipers. I was kicking myself for days. The rotors are 1/8" thinner, but I felt more comfortable replacing the wheel studs with longer ones from ARP.
The new rear wheels. Again Boyd Coddington Nemesis 18x9.5 with 4.75" backspacing and Kumho tires 275/40/18. Like I said earlier, the rotors are 1/8" thinner than stock. This moves the wheel that much closer to the trailing arm and gives the wheels an effective backspace of 4.875". There is over 1/2" between the tire sidewall and the stock trailing arm. The parking brake was removed completely during the install of the new rotors, however the bracket on the trailing arm fits inside the wheel and does not need to be removed. No spacer was required for the rear wheels.