Brake problems.

Its all a matter of mech advantages via pedal leverage and simple hydraulics/master cyl. area---wheel caliper area

And most brake problems are a miss match of selected components and/or the way they are orientated( prop vavves reversed,etc)

A couple recommended starting points are Manifold vaccume and line pressure front/rear---without acceptable ranges here the other points are moot!!!!!

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Originally Posted by jerry clayton

Its all a matter of mech advantages via pedal leverage and simple hydraulics/master cyl. area---wheel caliper area

And most brake problems are a miss match of selected components and/or the way they are orientated( prop vavves reversed,etc)

A couple recommended starting points are Manifold vaccume and line pressure front/rear---without acceptable ranges here the other points are moot!!!!!

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I understand what you are saying. All of the components are installed correctly and have been checked and doubled checked. However, this doesn't mean that they are properly matched. Mustang II front end, 11" ford rotors with matching calipers, rear ford drums (9" ford rear end), 7" booster, 1" bore master cylinder, proportion valve, residual valves (10 pound rear, 2 pound front). All components are new or rebuilt except for the proportion valve and residual valves. The only thing left to try that I know of is ordering a pressure gauge and obtain some pressure readings. I just need to know what pressures to expect for a proper operationg system.

Thanks,

Teddy

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Originally Posted by teddy

I understand what you are saying. All of the components are installed correctly and have been checked and doubled checked. However, this doesn't mean that they are properly matched. Mustang II front end, 11" ford rotors with matching calipers, rear ford drums (9" ford rear end), 7" booster, 1" bore master cylinder, proportion valve, residual valves (10 pound rear, 2 pound front). All components are new or rebuilt except for the proportion valve and residual valves. The only thing left to try that I know of is ordering a pressure gauge and obtain some pressure readings. I just need to know what pressures to expect for a proper operationg system.

Thanks,

Teddy

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Everything there should be just fine - but one question - do you have a check valve in the MC?? If so it has to come out if you have the resid and proportioning valves.

Also, a 7/8 or 15/16 MC might work better. At one point with a car, I had small single piston Wilwood's on the front and 15/16 wheel cylinders on the back along with a late Mustang 1"+ master cylinder. I ended up with a 7/8 mc and 7/8 rear cylinders and almost power brakes from virtually none.

And another, if you are using silicone brake fluid - don't. This is one fluid that has a very small amount of compressibility plus will react with any regular ethylene based fluid, causing the seals to expand - and a lousy pedal will be the result. Great stuff for racing, but not for a road car.

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Originally Posted by IC2

Everything there should be just fine - but one question - do you have a check valve in the MC?? If so it has to come out if you have the resid and proportioning valves.

Also, a 7/8 or 15/16 MC might work better. At one point with a car, I had small single piston Wilwood's on the front and 15/16 wheel cylinders on the back along with a late Mustang 1"+ master cylinder. I ended up with a 7/8 mc and 7/8 rear cylinders and almost power brakes from virtually none.

And another, if you are using silicone brake fluid - don't. This is one fluid that has a very small amount of compressibility plus will react with any regular ethylene based fluid, causing the seals to expand - and a lousy pedal will be the result. Great stuff for racing, but not for a road car.

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I don't know if the master cylinder has a check valve or not. I assume not since I purchased it from "Chassis Engineering". It is supposed to be a corvette master cylinder and is supposed to work with residual valves and a proportional valve. Before I made the purchase, I asked them about going to a 7/8" bore master cylinder because I heard if would provide more pressure (less volume, more pressure). They told me I need the 1" bore to provide enough volume for the front disc brakes. I made the purchase to replace my existing booster and master cylinder. Unfortunately it did not make any difference. I did play around with the rod adjustment from the booster to the master cylinder piston. I kept extending it into the master cylinder until it caused a drag on the front brakes. I found with some drag the brakes worked better but with a little more out ward adjustment it would cause the brakes to drag so much that I couldn't turn the front wheels by hand when I raised them off the ground. I have now backed the adjustment off to where the rod just barely pushes on the master cylinder piston and the brakes are probably the best they have been but still not as good as I think they should be.

Thanks,]

Teddy

Quote:

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Originally Posted by teddy

I don't know if the master cylinder has a check valve or not. I assume not since I purchased it from "Chassis Engineering". It is supposed to be a corvette master cylinder and is supposed to work with residual valves and a proportional valve. Before I made the purchase, I asked them about going to a 7/8" bore master cylinder because I heard if would provide more pressure (less volume, more pressure). They told me I need the 1" bore to provide enough volume for the front disc brakes. I made the purchase to replace my existing booster and master cylinder. Unfortunately it did not make any difference. I did play around with the rod adjustment from the booster to the master cylinder piston. I kept extending it into the master cylinder until it caused a drag on the front brakes. I found with some drag the brakes worked better but with a little more out ward adjustment it would cause the brakes to drag so much that I couldn't turn the front wheels by hand when I raised them off the ground. I have now backed the adjustment off to where the rod just barely pushes on the master cylinder piston and the brakes are probably the best they have been but still not as good as I think they should be.

Thanks,]

Teddy

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Teddy,
What you are saying is that you are "preloading" the brake hydraulic system by putting fluid down the lines to partially extend the caliper pistons. That would say to me that you have a mc that's too large as far as piston diameter. I really wonder if indeed you actually have a 1" or something larger. The 1" should be correct but remember, an OEM Corvette with power brakes has a 1 1/8" and you might be the victim of a screw up by Chassis Engineering's supplier. With manual brakes, the Corvette mc is 3/4" !!!! Sounds like something that needs some looking into

I would recommend a master from a late 60s ford that had front disc and rear drums---the corvette is for front/rear discs--these masters can be bought new for 60-70 dollars

Does the pedal feel good ? By that I mean spongy or too hard ?
One thing I have encountered in the past is front brake pads that are to hard, especially some of the metallic pads, and not just the cheapies I have seen problems in some of the top name stuff where the car just would not stop.
The answer after several hair pulling hours of diagnostic time was to simply switch the front pads to organic and the darn car would then throw ya thru the windshield.

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Originally Posted by IC2

Teddy,
What you are saying is that you are "preloading" the brake hydraulic system by putting fluid down the lines to partially extend the caliper pistons. That would say to me that you have a mc that's too large as far as piston diameter. I really wonder if indeed you actually have a 1" or something larger. The 1" should be correct but remember, an OEM Corvette with power brakes has a 1 1/8" and you might be the victim of a screw up by Chassis Engineering's supplier. With manual brakes, the Corvette mc is 3/4" !!!! Sounds like something that needs some looking into

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I will follow up on the master cylinder with Chassis Engineering tomorrow. I should have insisted on a smaller piston size.

Thanks

Teddy

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Originally Posted by HWORRELL

Does the pedal feel good ? By that I mean spongy or too hard ?
One thing I have encountered in the past is front brake pads that are to hard, especially some of the metallic pads, and not just the cheapies I have seen problems in some of the top name stuff where the car just would not stop.
The answer after several hair pulling hours of diagnostic time was to simply switch the front pads to organic and the darn car would then throw ya thru the windshield.

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I was asking a friend today if maybe another pad would work better. The pads I have look to be a metallic type. I may try to go to another pad after I talk to Chassis Engineering about possibly getting the wrong master cylinder as others have posted. Thank you for your input and I thank everyone else fore great responses. I am going out of town next Monday for maybe 6 to 8 weeks and if I don't get the problem resolved in the next few days it will have to go on the back burner for a while. When I get this problem resolved I will surely post again to let everyone know if and how it all works out.

Thanks to all,

Teddy