Disc Brakes Made Simple
Carmen Anastasio wants your old car to stop safely.
Story Brad Bowling - April 19, 2012 10:00 AM
1 Brackets such as this allow Master Power Brakes customers to convert from drums to disc without modifying or replacing their factory spindles.
2 The beauty of Carmen Anastasio’s brake kit concept is that it combines factory-spec equipment with a few well-engineered brackets and adaptors. The rotors, calipers, dual-reservoir master cylinder, and booster that make up this 1963 Pontiac kit are all OEM General Motors parts.
3 Anastasio studies brake parts by disassembling or dissecting them. The shelves in his workshop contain many cutaway brake components, such as this inferior aftermarket master cylinder. It has misaligned holes for fluid and a weak retention spring.
4 Raybestos built this master cylinder for GM, specifically for the Corvette. The fluid feed holes are perfectly aligned with the leading edge of the thin rubber cups so braking effect is immediate.
5 MPB sells this combination valve with its disc/drum conversion kits. Seen here in cutaway form, the single part contains mechanisms for proportioning flow front-to-rear, metering flow, and maintaining pressure differential. The metal spring (seen left) is for a car with front discs and rear drums. With approximately 150 pounds of resistance, its role is to momentarily delay the discs so the drums can make contact first and reduce the car’s braking dive. The white sensor installed in this photo is what triggers the light on your dashboard indicating a problem with the brake system. When its metal probe touches either part of the hourglass-shaped plunger (due to thin brake pads or low fluid levels), it grounds the terminal.
6 Take a look at this combination valve Anastasio shows people when they are tempted to save a few dollars on their project. The three components are badly misaligned and will not function with any reliability.
7 For car owners converting to an all-disc system, the simpler metering valve-only mechanism (top) can replace the combination valve.
8 There was a period in the 1990s when inventors tried to fit mechanical anti-lock brake systems (ABS) to older cars. This valve from Anastasio’s collection was supposed to prevent lockup, but a rubber bladder inside the cylinder simply softened the pedal feel, giving the driver the impression of a modern ABS. It did not work.
9 Brake problems can often be traced to the least obvious part of the system – the pedal. Anastasio has a collection of “custom” brake pedal arms car owners have sent him.
10 This Frankenstein’s monster looks like something we might have made on the first day of shop class. Notice the bracket welded to the rod to reinforce it. If a rod is bending under the pressure of braking, it is time to consult an expert.
11 The owner of this pedal assembly knew he had a disaster waiting to happen. Not only was the geometry all wrong for activating the new brake system, but the metal was fatigued and ready to snap.
12 Anastasio is very particular about the rotors he chooses for his kits. He does not like brake rotors when the vent blades are thicker on one side than the other. They lead to inefficient heat transfer that can wear out – in this case – the inboard pads quicker. There should be 37 vent blades in each rotor.
13 With experience drawn from more than four decades in the brake business, Anastasio only uses German-made Pentosin fluid. He is not a fan of silicone-based fluid.
Carmen Anastasio, the mind behind Master Power Brakes in Mooresville, North Carolina, has spent his adult life making collector cars stop better.
For three decades, his carefully engineered kits have made it possible for thousands of owners to convert their all-drum classics to front power disc systems based on OEM components.
“Many years ago, I went to a shop in Lindenhurst, New York, to get a rebuilt power brake booster for my daughter’s car. The owner told me he wanted to sell the business and retire, so I bought it,” he said. “I was content remanufacturing brake components for individual customers and fleet accounts until two things happened in 1983 that changed everything.”
Anastasio wanted to fit power disc brakes to his ’57 Chevy. “It was important that I use stock GM parts, so I spent eight months doing the conversion,” he explained. “I had to make brackets that would work with the stock spindles, and I used our Bendix testing machines to evaluate how each part affected the flow of brake fluid. I knew how the individual modern components worked, but installing them on a 25-year-old car took a lot of research and development time. It was a learning experience.”
When he was finished, the Chevy stopped like a new car. He realized there was probably a market for it. The ’55-’57 Chevys were becoming really popular with the modified crowd, so Anastasio went into business selling complete kits by mail order.
During that same period, Federal-Mogul had bought out Carter’s power brake business and had 30,000 brand new boosters in a warehouse. Anastasio was there to buy some cores and saw they had 3,500 Chevy Vega boosters and wondered who would ever need that many Vega parts. “I realized the Vega booster was identical to the unit Chevy put on the 1964-’67 Corvettes. No one was restoring or even driving a Vega by that point, so I bought them all very cheaply and produced a Corvette brake kit, again using all OEM parts. The income from those Corvette kits made it possible to move into a bigger building.”
The demand was immediate. “Not only were we selling ’57 Chevy and Corvette kits, but people were calling every day asking about brakes for ’59 Chevys and ’63 Fords or whatever. I spent a lot of time in junkyards buying factory spindles to use for templates, and I cut up a lot of firewalls so I could fit master cylinders and pedals to them.”
Chryslers were the hardest to figure out because there were so many variations. “At shows, I would crawl under Mopars to figure out which ones had calipers in front or in back and which models had sway bars that would interfere with certain parts. Fortunately, a good friend of mine was a Chrysler engineer, and he gave me advice that let us develop a basic spindle kit that fit every model for about 10 years.”
It all starts with the brake pedal, but Anastasio did not know anything about pedal geometry when making that first kit. “I thought all pedals were the same and that it didn’t matter how long the arm was or where the master cylinder rod connected to it. The pedal is nothing but a lever. It multiplies foot pressure so the average human can easily stop a car. Your foot presses against the pad; that’s the load. The pivot acts like a fulcrum. The part the rod attaches to is the effort. Changing any part of an original brake pedal will either increase or decrease how much force the rod receives. Too much force makes the brakes grab quickly; too little makes it hard to stop the car.”
Brake systems are designed with a very specific ratio in mind. For instance, a non-boosted system in a 1960s car might use a 6:1 ratio, which means that six pounds of effort is created for every one pound the driver’s foot places against the pad. A boosted system would require less input from the driver, so a 4:1 ratio would be more appropriate.
“I spent two weeks experimenting with that ’57 Chevy before I realized that the factory’s power-boosted cars had different pedal mount points for the rod than the non-boosted cars. I drilled a hole one inch lower on the arm, and it worked. I had found the correct factory ratio for a ’57 Chevy with power brakes.
“At Master Power Brakes, we answer car owners’ questions about our kits. If the owner feels the components are not working properly, we almost always can narrow it down to a problem with the pedal. You would be surprised to see some of the brake pedals owners send us for inspection. Most of them look like they have been cut and welded together with parts somebody found lying around the garage.”
There’s a reason for different master cylinder bore sizes and booster diameters. The choices engineers make almost always boil down to vehicle weight. The most common bore sizes used with old cars are one inch and 11/8-inch, but there are others, depending on purpose. Boosters range from seven to 11 inches in diameter, and there are dual-diaphragm units that increase pressure without resorting to a bigger diameter. Atmospheric pressure – 14.7 psi at sea level – times the diameter of the booster equals the amount of assist. You certainly don’t want to over-assist a car’s brakes.
“Take a look at these master cylinder cutaways (photos 3 and 4) One is a foreign-made aftermarket part, and the other is OEM. The foreign-made unit has a retention spring so loose that you can activate the piston with your thumb. Just the weight of the brake pedal can have you riding down the road with the brakes on. The aftermarket part also has the rubber cup gaskets partially blocking the fluid from the reservoir above, which means you could get half a pedal before pressurizing the system. The OEM cutaway shows very precise machining, reservoir holes that are the proper 1/40,000-inch, and a sturdy return spring. This design has been field-tested on millions of GM cars and trucks; why would you use anything else?”
It is also essential that the bore be as smooth as glass. Special tools are required to get it right. Some master cylinders are honed and that’s wrong. Any texture inside will interfere with the smooth operation and reliability of the master cylinder piston.
Brake Fluid and Pads
Anastasio says brake fluid is another aspect that gets people in trouble with their brakes. “A few years ago, we started getting complaints about defective master cylinders. We investigated and found out there was a bad batch of brake fluid on the market; that fluid has since been taken off the market. The fluid wasn’t lubricating the master cylinder pistons, and that’s a major part of its job.
“There is also a common misconception about brake fluid types. We recommend DOT 4 fluid – not the silicone/petroleum-based stuff – to our customers. Silicone fluid attacks the EPDM rubber gaskets inside the master cylinder, which ruins the system. It’s like putting transmission fluid into your brake lines; it expands the rubber parts and they wear out. The silicone fluid does not mix with or absorb moisture. Moisture is unavoidable. It occurs when the brakes heat up and cool down, which happens thousands of times. As regular brake fluid ages, it absorbs this condensation and dilutes it throughout the system. With silicone, the water builds up in pockets within the system, usually in the wheel cylinders.”
Anastasio recommends changing your brake fluid every year. Do not fill master cylinders to the rim. A hot engine will expand the brake fluid in the full chamber, causing it to push down through the replenishing hole, which pressurizes the master cylinder and puts on the brakes.
The Master Power Brake kits use as many OEM parts as possible because they are well engineered and tested, and you can get replacements at any parts store or dealership around the country.
Everybody hates when a car needs its second set of brake pads because they expect the new pads won’t be as good as what came from the factory. “There’s this myth that the public can’t buy the same pads the factories install. Tell your shop you want the OEM pads, no matter what they cost, if you want the car to stop, look, and sound like it did when you bought it.
“Cheap is expensive. I used to fix the brakes on fleets of cars in New York. The city had 632 ambulances on the road every day, and they were wearing out pads. To save money, the purchasing department had bought a lot of undersized vehicles and overloaded them. We upgraded their pads and wheel cylinder size and it solved the problem. The same thing happened with their police cars. Pads were wearing out at 3,000 miles – we improved pads and wheel cylinders and suddenly they got 48,000 miles out of a set. You can save money on your car; just don’t try to do it the cheap way.”
“Four-piston or six-piston calipers are great for race cars, but they don’t have the clamping force for the street,” he said. “Remember, a race car seldom needs to come to a complete stop; it just has to slow down in a hurry.
“Race car rotors create a tremendous amount of heat. With a large single piston pushing against the pads, the center of the pad is hard against the rotor, but the ends can lift off the surface and reduce braking force and kill reliability. Distributing smaller pistons makes the pad press evenly against the rotor, but six small pistons can’t clamp down with as much force as the large single.
“A multi-piston caliper will have from 700 to 1,200 pounds of clamping force. The large single can apply as much as 3,000 pounds.”
“You can use 3/16-inch line throughout the car,” said Anastasio. “You can use rubber or stainless steel-braided hoses. You don’t want too much braided hosing in your system, because it flexes. It’s just a piece of plastic Teflon inside with the braiding on the outside. We’ve had people put it from the master cylinder to the hard lines; they get a mushy pedal. If you cut open an original equipment hose, there is layering and braiding inside. When you change a caliper, you should change the hose from the caliper because they wear out as the wheels turns back and forth.”
Vacuum and Brakes
“We’ve had a lot of problems with people not having their timing set properly when they install one of our power booster kits. You have to have a minimum of 18 inches of vacuum for the booster to work properly. It depends on what kind of booster it is. If we install a dual-diaphragm nine-inch unit, the system works fine with 15 inches of boost. If the engine still isn’t producing enough vacuum, then we sell a vacuum pump.
“If a customer brings in a car with complaints about the power-assist system, the first thing we do is check the vacuum. We always adjust the engine’s timing with a vacuum gauge, not a timing light. When you have your highest vacuum reading, that means the engine is at its most efficient in terms of combustion.
“We had three people come in with Ford engines that were supposedly dyno tested. I put the vacuum gauge on it and found the problem right away. The timing was off.”
In closing, Anastasio stresses simplicity. “Brakes are easy. Brakes are basic. People get into trouble when they try to outsmart the factory engineers.”
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