72 brakes

[Chuck G.]

Re: 72 brakes and a few CAUTIONS

There is yet another option, and that is the "O" ring brake caliper pistons. In the standard system, the pads "ride" on the rotor...both sides, held against the rotor by the springs behind the pistons.

If you use the "O" ring design caliper pistons, you do not use the springs behind the pistons, but more importantly, the "O" ring design will hold the piston back, not allowing the pad to ride on the rotor. Thus, you can live with some rotor runout, as the pads won't ride on the rotor and pump air.

I fought this issue on my 69 for some time, before a complete suspension/brake rebuild a few years ago. I replaced my original caliper pistons with the "O" ring style, and that eliminated my problem. I finally had the rotors turned on the front hubs and rear spindles, but still kept the "O" ring pistons.

Terry might remember helping me bleed my brakes on the road tour to Bowling Green a few years ago. Completely lost my pedal beginning the last leg of the tour. Terry, Jim Romano, and a few others helped Pat and I do a NASCAR style brake bleed. Had all 4 wheels done in about 10 minutes. Chuck

[Terry M.]

Re: 72 brakes and a few CAUTIONS

Craig, I am not aware of any brake lathe that will turn the rotors with the spindle attached, however, there are numerous "on-the-car" lathes that will refinish the rotors while they are installed on the car. These are quite common because some front wheel drive cars require this kind of service. On these cars removal of the front rotors requires the front wheel bearings to be destroyed, so refinishing the rotors on the car makes sense. In these cases the rotors are turned by the vehicles drive train, and that would accomplish the desired results on the rear of a C2 or C3. Generally, these machines are built so that they can accomplish their job in spite of the proximity of steering components, but a brake shop is not likely to have experience with the rear brakes on a Corvette so some openness to innovation will be necessary on the part of the shop employees. A call, or better yet drop in and talk to them, before you show up on their driveway with your pride and joy will help the process. Alternately a shop with Corvette experience might have used this process....... If there is a good Corvette shop in your neighborhood you might inquire there.
Chuck, I do recall the brake bleed on your 1969 on the way to Bowling Green. That is one of the fun parts of the road tour - perhaps not so much fun for the driver, but for the other participants. Glad the o-ring style conversion solved the problem.

[Mike McKown]

Re: 72 brakes

If your brakes are truly "coming and going", hard pedal/soft pedal, and your brake light comes on "sometimes", I wouldn't be looking for air in the lines. I'd be looking for another master cylinder. If you get air in the lines, you will have a soft pedal ALL the time along with the brake light coming on.

[Al S.]

Re: 72 brakes

Tom,
Regardless of the cause of how the air is getting in, you'll still have to bleed the system.
Try gravity bleeding.
Place a jar or can at each wheel with a few inches of brake fluid in them. Get some clear tubing like they use in a tropical fish store, open all the bleeders and stick the tubing on each bleeder screw with the other end in the can or jar. Make sure there's enough fluid covering the tubing in the jar so you don't get air going backwards towards the bleeder screw, then let gravity do the work. Periodically check your progress at each wheel and you will actually see the fluid slowly moving through the hoses and an occasional air bubble in the tubing. I let mine sit almost two days before I pressure bled them and it worked like a charm. Just keep topping the master cylinder off during the process.
Another trick is don't pump the pedal while pressure bleeding, just hold it down once, crack the bleeder screw, close the bleeder screw, then release the brake pedal. Pumping the brake pedal aggitates the air and makes it harder to get out.
Good luck.

[Harmon C.]

Re: 72 brakes

I was a fan of gravity bleading but if you buy a rebuilt M/C that is sleved they will not gravity blead because the sleve covers the hole that alowed it to happen. Lyle

[John H.]

Re: 72 brakes

Don't understand that - the fluid path for gravity bleeding is the same as the path for normal replenishment from the reservoirs through the compensating ports to the primary and secondary bore areas forward of the piston seals, and from there directly to the outlet ports.