73 brake calipers
Thread Starter
Racer
Joined: Apr 2004
Posts: 336
Likes: 0
From: Tucson
73 brake calipers
Many. many years ago, I purchased remanufactured brake calipers from a well know Vette brake company. At the time I didn't know much about Vettes. As it turned out, the rear calipers I got have 2 bleeder screws each, but the documentation I've seen for the 68-77 years only have 1 bleeder per caliper. Was I given the incorrect caliper? Does this have significant effect?
I rarely drive my car (500 miles a year), but I have to bleed the brakes a lot often then should be necessary. I live in a desert climate and my car never experiences freezing temp.
Thanks.
I rarely drive my car (500 miles a year), but I have to bleed the brakes a lot often then should be necessary. I live in a desert climate and my car never experiences freezing temp.
Thanks.
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
C3 rear brake calipers have two bleeder screws, an inner and an outer. Front calipers have only one.
Rotor run-out is typically the cause of air in the brake system where no leaks, etc., can be found. Very common.
Rotor run-out is typically the cause of air in the brake system where no leaks, etc., can be found. Very common.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Have you checked run out on the rotors? If run out is out of spec, the brakes can pump air, requiring frequent bleeding.
Last edited by Easy Mike; Feb 25, 2014 at 11:13 AM.
Thread Starter
Racer
Joined: Apr 2004
Posts: 336
Likes: 0
From: Tucson
Thanks guys. I'll check with the person who did brake work for me a couple of years ago and see if he has any record of turning the rotors. After that I'll pull the rotors and have them checked and turned if necessary.
My source was my Haynes Chevrolet Corvette Automotive Repair Manual (#274) published in 1991, page 9-12, section 7.
My source was my Haynes Chevrolet Corvette Automotive Repair Manual (#274) published in 1991, page 9-12, section 7.
Last edited by Ran-D; Feb 25, 2014 at 01:52 AM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Haynes manual information is always "suspect". If you have a copy of the Chevrolet Chassis Service Manual, you can toss that Haynes in "file 13". (Well, don't really do that; just put it at the bottom of the book pile. It's pretty useless.)
Thread Starter
Racer
Joined: Apr 2004
Posts: 336
Likes: 0
From: Tucson
I don't have any record of the rotors ever being turned, it was my '01 rotors that were turned. I'm doubtful anyone within a hundred miles of me is able to check them on the car, but worth an ask before turning.
Thanks.
Thanks.
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Drifting
Joined: Jul 2008
Posts: 1,873
Likes: 27
From: Sonora CA
Check out this thread, it will / could / might/ maybe answer a lot of questions.........
http://forums.corvetteforum.com/c3-g...le-runout.html
http://forums.corvetteforum.com/c3-g...le-runout.html
Burning Brakes
Joined: Aug 2004
Posts: 802
Likes: 1
Thanks guys. I'll check with the person who did brake work for me a couple of years ago and see if he has any record of turning the rotors. After that I'll pull the rotors and have them checked and turned if necessary.
My source was my Haynes Chevrolet Corvette Automotive Repair Manual (#274) published in 1991, page 9-12, section 7.
My source was my Haynes Chevrolet Corvette Automotive Repair Manual (#274) published in 1991, page 9-12, section 7.
Turning needs to be done on the car since the tolerances for the disc and brg assy function as a single unit.
Steve L
73 coupe since new
Race Director
Joined: Jul 2001
Posts: 15,892
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Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
I'll try.
The lip seal on the piston in the caliper is designed so that the pressure of the brake fluid pushes the seal tightly against the cylinder. Rotor runout causes the pistons in the caliper to be pushed back into the cylinder. There is a spring behind the piston that pushes the piston toward the brake pad. Without the pressure from the fluid to push the seal against the cylinder wall, the piston goes toward the brake pad and a small amount of air slips in past the lip seal. It is just a very small amount of air per revolution of the wheel but over many hundreds or thousands of revolutions a significant amount of air can slip past the lip seals.
That's why many owners convert to O-ring seals. They do not depend on the pressure from the brake fluid to make the seal air tight.
The lip seal on the piston in the caliper is designed so that the pressure of the brake fluid pushes the seal tightly against the cylinder. Rotor runout causes the pistons in the caliper to be pushed back into the cylinder. There is a spring behind the piston that pushes the piston toward the brake pad. Without the pressure from the fluid to push the seal against the cylinder wall, the piston goes toward the brake pad and a small amount of air slips in past the lip seal. It is just a very small amount of air per revolution of the wheel but over many hundreds or thousands of revolutions a significant amount of air can slip past the lip seals.
That's why many owners convert to O-ring seals. They do not depend on the pressure from the brake fluid to make the seal air tight.
Safety Car
Joined: Dec 2007
Posts: 4,229
Likes: 39
From: Beautiful East Texas
If that's the case, it seems that air would be getting in the system each time the brake were applied and released as the caliper pistons move back & forth.
Thanks for the explanation... and I'm not trying to be argumentative, as a new C3 owner, I'm trying to glam on to all the brake system knowledge I can.
mardyn
Thanks for the explanation... and I'm not trying to be argumentative, as a new C3 owner, I'm trying to glam on to all the brake system knowledge I can.
mardyn
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
No, the seals act as a one-way check valve in the above scenario. The correct solution is to eliminate or reduce rotor run-out. Bubba frequently makes things worse by swapping rotors or machining them separately from the hubs/spindles.
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
I can't get the lines to line up properly but hopefully this helps
\
| It's hard to explain in but the seal is shaped somewhat like the lines at the left. When
| fluid is pushing from the left, the two diagonal lines are forced outward against the
| cylinder walls. When returning, the friction against the wall keeps the seal against it.
/
_
| When pushed forward by the spring with no fluid pressure against the seal, the edge
| of the lip can flex inward as shown on the top of the diagram at the left. This allows
| the air to enter the cylinder.
/
\
| It's hard to explain in but the seal is shaped somewhat like the lines at the left. When
| fluid is pushing from the left, the two diagonal lines are forced outward against the
| cylinder walls. When returning, the friction against the wall keeps the seal against it.
/
_
| When pushed forward by the spring with no fluid pressure against the seal, the edge
| of the lip can flex inward as shown on the top of the diagram at the left. This allows
| the air to enter the cylinder.
/
Last edited by my 76 ray; Mar 10, 2014 at 04:11 PM.
