C3 Brakes
Thread Starter
Intermediate
Joined: Oct 2012
Posts: 39
Likes: 0
this is good to know, now that i have a baseline i will be stopping in no time.
Burning Brakes
Joined: May 2008
Posts: 1,116
Likes: 5
From: Middleburg Florida
Corey, welcome to C3 corvettes!! You're experiencing one of the unique issues with these cars. The brake systems on C3's are very good even by today's standards. The issue is that usually they aren't working properly and people start throwing aftermarket parts at them to "increase performance". This usually isn't necessary at all for street driven cars.
The C3s have fixed calipers that have pistons on both the inside and outside halves of them. This means that rotor runout is very important. If you have more than a few thousandths of an inch of runout in the rotors, the pistons pulse and suck air at the piston seals. There is some discussion on the piston seals themselves as well. The factory installed standard lip seals and they worked well for a long time. Then someone started putting O-ring seals in as a replacement, and there are folks who like that approach. As far as I can tell, they both work find. The calipers are typically fitted with stainless steel sleeves in the piston bores now to prevent corrosion and increase longevity. Finding calipers that aren't sleeved is becomming more and more rare. Any replacement calipers you buy will typically be sleeved. If you have the choice, choose the sleeved calipers when replacing yours if you have to. The calipers are in two pieces. There's a small o-ring that seals the passages from one side to the other, this is another area that can leak. If your calipers are leaking, they usually leak from the pistons first, then through the dust boots around the pistons, and then they can leak between halves. Overall though, once these are rebuilt correctly, they last for years and years, probably longer than you'll own the car!
The rotors on these cars are riveted in place. Why? Because of the runout issue described earlier. These rotors aren't like the consumable rotors out today. They didn't usually need replaced or even turned, just the glaze broken. Removing these from the hubs is a job. You have to remove the rivets, do what ever it is you're going to do, and reinstall them making sure your runout is less than .003. I think that's the right spec, it'd have to be verified.
Another area of concern on these cars is the rubber brake hoses on each corner. Those aren't usually replaced and they wear over the years.....from the inside out. You can't see the wear, and when they go bad they usually colapse causing no brake fluid pressure to that corner. If you rebuild your brakes system, check and replace these as necessary.
And then there's the master cylinder. It's a big capable piece that doesn't require any special attention with the exception that you MUST bench bleed a new/rebuilt unit before installation. This isn't unique to C3's but it has to be done. You can do it before you install it, our after you install it and remove it again, but you're gonna do it! The vacuum booster on these cars is a standard vacuum booster, nothing special here either.
Bleeding. The other unique beast on a C3 brake system. You bleed these systems using what ever method you like, gravity, pump and hold, power bleeder, or vacuum method. The key is to start at the rear, and bleed the inner caliper half on the side your working first. Then move to the outter half, bleeding each caliper completly before moving to the other side. I start on the passenger side of the car first, farthest from the master cylinder. The front calipers only have one bleeder so you bleed them like any other brake system.
So there you have it Corey. If your brake system is working properly, it'll stand the car on it's nose (not really, these things don't nose dive much!..
). The pedal pressure won't be as easy as the late model hydroboost systems (some have done hydroboost conversions to C3's though), because it's a vacuum assist, not hydraulic, but it'll work very very well.
The C3s have fixed calipers that have pistons on both the inside and outside halves of them. This means that rotor runout is very important. If you have more than a few thousandths of an inch of runout in the rotors, the pistons pulse and suck air at the piston seals. There is some discussion on the piston seals themselves as well. The factory installed standard lip seals and they worked well for a long time. Then someone started putting O-ring seals in as a replacement, and there are folks who like that approach. As far as I can tell, they both work find. The calipers are typically fitted with stainless steel sleeves in the piston bores now to prevent corrosion and increase longevity. Finding calipers that aren't sleeved is becomming more and more rare. Any replacement calipers you buy will typically be sleeved. If you have the choice, choose the sleeved calipers when replacing yours if you have to. The calipers are in two pieces. There's a small o-ring that seals the passages from one side to the other, this is another area that can leak. If your calipers are leaking, they usually leak from the pistons first, then through the dust boots around the pistons, and then they can leak between halves. Overall though, once these are rebuilt correctly, they last for years and years, probably longer than you'll own the car!
The rotors on these cars are riveted in place. Why? Because of the runout issue described earlier. These rotors aren't like the consumable rotors out today. They didn't usually need replaced or even turned, just the glaze broken. Removing these from the hubs is a job. You have to remove the rivets, do what ever it is you're going to do, and reinstall them making sure your runout is less than .003. I think that's the right spec, it'd have to be verified.
Another area of concern on these cars is the rubber brake hoses on each corner. Those aren't usually replaced and they wear over the years.....from the inside out. You can't see the wear, and when they go bad they usually colapse causing no brake fluid pressure to that corner. If you rebuild your brakes system, check and replace these as necessary.
And then there's the master cylinder. It's a big capable piece that doesn't require any special attention with the exception that you MUST bench bleed a new/rebuilt unit before installation. This isn't unique to C3's but it has to be done. You can do it before you install it, our after you install it and remove it again, but you're gonna do it! The vacuum booster on these cars is a standard vacuum booster, nothing special here either.
Bleeding. The other unique beast on a C3 brake system. You bleed these systems using what ever method you like, gravity, pump and hold, power bleeder, or vacuum method. The key is to start at the rear, and bleed the inner caliper half on the side your working first. Then move to the outter half, bleeding each caliper completly before moving to the other side. I start on the passenger side of the car first, farthest from the master cylinder. The front calipers only have one bleeder so you bleed them like any other brake system.
So there you have it Corey. If your brake system is working properly, it'll stand the car on it's nose (not really, these things don't nose dive much!..
). The pedal pressure won't be as easy as the late model hydroboost systems (some have done hydroboost conversions to C3's though), because it's a vacuum assist, not hydraulic, but it'll work very very well.
Thread Starter
Intermediate
Joined: Oct 2012
Posts: 39
Likes: 0
Corey, welcome to C3 corvettes!! You're experiencing one of the unique issues with these cars. The brake systems on C3's are very good even by today's standards. The issue is that usually they aren't working properly and people start throwing aftermarket parts at them to "increase performance". This usually isn't necessary at all for street driven cars.
The C3s have fixed calipers that have pistons on both the inside and outside halves of them. This means that rotor runout is very important. If you have more than a few thousandths of an inch of runout in the rotors, the pistons pulse and suck air at the piston seals. There is some discussion on the piston seals themselves as well. The factory installed standard lip seals and they worked well for a long time. Then someone started putting O-ring seals in as a replacement, and there are folks who like that approach. As far as I can tell, they both work find. The calipers are typically fitted with stainless steel sleeves in the piston bores now to prevent corrosion and increase longevity. Finding calipers that aren't sleeved is becomming more and more rare. Any replacement calipers you buy will typically be sleeved. If you have the choice, choose the sleeved calipers when replacing yours if you have to. The calipers are in two pieces. There's a small o-ring that seals the passages from one side to the other, this is another area that can leak. If your calipers are leaking, they usually leak from the pistons first, then through the dust boots around the pistons, and then they can leak between halves. Overall though, once these are rebuilt correctly, they last for years and years, probably longer than you'll own the car!
The rotors on these cars are riveted in place. Why? Because of the runout issue described earlier. These rotors aren't like the consumable rotors out today. They didn't usually need replaced or even turned, just the glaze broken. Removing these from the hubs is a job. You have to remove the rivets, do what ever it is you're going to do, and reinstall them making sure your runout is less than .003. I think that's the right spec, it'd have to be verified.
Another area of concern on these cars is the rubber brake hoses on each corner. Those aren't usually replaced and they wear over the years.....from the inside out. You can't see the wear, and when they go bad they usually colapse causing no brake fluid pressure to that corner. If you rebuild your brakes system, check and replace these as necessary.
And then there's the master cylinder. It's a big capable piece that doesn't require any special attention with the exception that you MUST bench bleed a new/rebuilt unit before installation. This isn't unique to C3's but it has to be done. You can do it before you install it, our after you install it and remove it again, but you're gonna do it! The vacuum booster on these cars is a standard vacuum booster, nothing special here either.
Bleeding. The other unique beast on a C3 brake system. You bleed these systems using what ever method you like, gravity, pump and hold, power bleeder, or vacuum method. The key is to start at the rear, and bleed the inner caliper half on the side your working first. Then move to the outter half, bleeding each caliper completly before moving to the other side. I start on the passenger side of the car first, farthest from the master cylinder. The front calipers only have one bleeder so you bleed them like any other brake system.
So there you have it Corey. If your brake system is working properly, it'll stand the car on it's nose (not really, these things don't nose dive much!.. ). The pedal pressure won't be as easy as the late model hydroboost systems (some have done hydroboost conversions to C3's though), because it's a vacuum assist, not hydraulic, but it'll work very very well.
The C3s have fixed calipers that have pistons on both the inside and outside halves of them. This means that rotor runout is very important. If you have more than a few thousandths of an inch of runout in the rotors, the pistons pulse and suck air at the piston seals. There is some discussion on the piston seals themselves as well. The factory installed standard lip seals and they worked well for a long time. Then someone started putting O-ring seals in as a replacement, and there are folks who like that approach. As far as I can tell, they both work find. The calipers are typically fitted with stainless steel sleeves in the piston bores now to prevent corrosion and increase longevity. Finding calipers that aren't sleeved is becomming more and more rare. Any replacement calipers you buy will typically be sleeved. If you have the choice, choose the sleeved calipers when replacing yours if you have to. The calipers are in two pieces. There's a small o-ring that seals the passages from one side to the other, this is another area that can leak. If your calipers are leaking, they usually leak from the pistons first, then through the dust boots around the pistons, and then they can leak between halves. Overall though, once these are rebuilt correctly, they last for years and years, probably longer than you'll own the car!
The rotors on these cars are riveted in place. Why? Because of the runout issue described earlier. These rotors aren't like the consumable rotors out today. They didn't usually need replaced or even turned, just the glaze broken. Removing these from the hubs is a job. You have to remove the rivets, do what ever it is you're going to do, and reinstall them making sure your runout is less than .003. I think that's the right spec, it'd have to be verified.
Another area of concern on these cars is the rubber brake hoses on each corner. Those aren't usually replaced and they wear over the years.....from the inside out. You can't see the wear, and when they go bad they usually colapse causing no brake fluid pressure to that corner. If you rebuild your brakes system, check and replace these as necessary.
And then there's the master cylinder. It's a big capable piece that doesn't require any special attention with the exception that you MUST bench bleed a new/rebuilt unit before installation. This isn't unique to C3's but it has to be done. You can do it before you install it, our after you install it and remove it again, but you're gonna do it! The vacuum booster on these cars is a standard vacuum booster, nothing special here either.
Bleeding. The other unique beast on a C3 brake system. You bleed these systems using what ever method you like, gravity, pump and hold, power bleeder, or vacuum method. The key is to start at the rear, and bleed the inner caliper half on the side your working first. Then move to the outter half, bleeding each caliper completly before moving to the other side. I start on the passenger side of the car first, farthest from the master cylinder. The front calipers only have one bleeder so you bleed them like any other brake system.
So there you have it Corey. If your brake system is working properly, it'll stand the car on it's nose (not really, these things don't nose dive much!..
). The pedal pressure won't be as easy as the late model hydroboost systems (some have done hydroboost conversions to C3's though), because it's a vacuum assist, not hydraulic, but it'll work very very well.
Instructor
Joined: Apr 2011
Posts: 167
Likes: 0
From: Jacksonville Florida
Coreyt - Very informative, thanks. The only thing I would add is that the booster can be ruled out. If it weren't working right the pedal would be real firm without any braking effect.
OP - I have had the same issues you are experiencing and it took a lot of effort to bleed the brakes completely. I eventually got them bled all of the way by the gravity method. It was the first time I have ever done it that way on any car. I wasn't certain how well it would work but it turned out the most effective. My brakes on my 77 are better than either one of my 2000+ vehicles. Except ALB of course.
OP - I have had the same issues you are experiencing and it took a lot of effort to bleed the brakes completely. I eventually got them bled all of the way by the gravity method. It was the first time I have ever done it that way on any car. I wasn't certain how well it would work but it turned out the most effective. My brakes on my 77 are better than either one of my 2000+ vehicles. Except ALB of course.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Yes. The rotors will last a long time, as long as you never run the pads so thin that the rivets scratch them.
The rotors on my 74 smallblock have never been turned. They have 170,000 miles on them.
And if you jump on the brakes hard, your sunglasses could hit the windshield.......
The rotors on my 74 smallblock have never been turned. They have 170,000 miles on them.
And if you jump on the brakes hard, your sunglasses could hit the windshield.......
Last edited by gcusmano74; Nov 5, 2012 at 09:20 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Inspect the rotors to see if they are smooth, or if they have a lot of uneven wear and/or grooving. Also look to see if there are any brake fluid leaks that could be dripping flluid onto a rotor or disc pad. If that happens, the pad will glaze-over and provide little stopping action.
If the rotors are in reasonably good shape and there are no fluid leaks onto the rotors/pads, then it is most likely that your braking power is limited by very poor quality brake pads. Causing the tires to lock-up should be no problem with brake system in decent condition, good quality pads, and stock tires. If you have very wide, grippy tires, that might be more difficult.
There are many good quality brake pads out there. The ones with the best stopping power are very abrasive and will create a lot of nasty brake pad dust that is filthy on your wheels and difficult to clean; most are metallic or semi-metallic pads. There are also some ceramic pads that don't provide quite the stopping power, but don't make the kind of black dust that metallics make. Go to NAPA and ask what your options are. Or, research the issue on the internet until you decide on a pad that meets your needs.
If you have air in the brake lines, the pedal will feel spongy and you will never build the kind of pressure needed to have crisp stopping action. And bleeding the C3 brake system is not a simple process. Use the SEARCH function on this Forum to read about how to bleed the brakes, if you have a 'spongy' pedal.
Lastly, if someone installed the wrong master cylinder on your car (in earlier times), your system may not be able to generate the fluid pressures that a stock car can produce. I'm not quite sure how you check that out, as different M/C's may use the same casting to make the housings. The difference is in the valve spool sizes, internally. Others may be able to advise you better on this one.
If the rotors are in reasonably good shape and there are no fluid leaks onto the rotors/pads, then it is most likely that your braking power is limited by very poor quality brake pads. Causing the tires to lock-up should be no problem with brake system in decent condition, good quality pads, and stock tires. If you have very wide, grippy tires, that might be more difficult.
There are many good quality brake pads out there. The ones with the best stopping power are very abrasive and will create a lot of nasty brake pad dust that is filthy on your wheels and difficult to clean; most are metallic or semi-metallic pads. There are also some ceramic pads that don't provide quite the stopping power, but don't make the kind of black dust that metallics make. Go to NAPA and ask what your options are. Or, research the issue on the internet until you decide on a pad that meets your needs.
If you have air in the brake lines, the pedal will feel spongy and you will never build the kind of pressure needed to have crisp stopping action. And bleeding the C3 brake system is not a simple process. Use the SEARCH function on this Forum to read about how to bleed the brakes, if you have a 'spongy' pedal.
Lastly, if someone installed the wrong master cylinder on your car (in earlier times), your system may not be able to generate the fluid pressures that a stock car can produce. I'm not quite sure how you check that out, as different M/C's may use the same casting to make the housings. The difference is in the valve spool sizes, internally. Others may be able to advise you better on this one.
Last edited by 7T1vette; Nov 5, 2012 at 09:57 PM.
Intermediate
Joined: Dec 2011
Posts: 26
Likes: 0
From: Newport News VA
Oops...don't press the tab key for punctuation! Anyway, my pedal is about 2 inches from the firewall when the brakes engage. I've replace the booster and m/c and done a full bleed. Brakes are great the pedal just seems to be a little close to the firewall.
I'm thinking that the rod connecting the pedal to the m/c has been replaced with a shorter on sometime in the past.
Any of y'all been around this one before?
I'm thinking that the rod connecting the pedal to the m/c has been replaced with a shorter on sometime in the past.
Any of y'all been around this one before?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
All you need is to have a slight amount of freeplay. If you need to move the pedal any more than 1/4" before the rod touches the master cylinder piston, adjust it. It needs to come away clear when the pedal is not depressed.
