Tips On Building A Complete Brake System For Your Hot Rod

Part 2: Avoid These Brake System Blunders!

By Ron Ceridono – Photography by Ron Ceridono and Courtesy of Wilwood, Classic Performance Products & Speedway Motors

There are some shortcomings in a hot rod you can learn to live with. An occasional rattle, a window crank that comes off in your hand, or a gas gauge that never seems to be quite right. One thing you may not live with is a malfunctioning brake system. If you are building or buying a car, here are some things to consider:

02 Now available from Speedway Motors is this nickel_copper (NiCopp) inverted flare brake line kit — Now available from Speedway Motors is this nickel/copper (NiCopp) inverted flare brake line kit. It includes a 25-foot roll of tubing, 3/8-24 inverted flare threaded tube nuts, and a Titan flaring tool.

Picking the Proper Brake Line Tubing

A brake system may produce well over 1,000 psi in operation, which requires brake lines, hoses, and fittings that can withstand pressure reliably—that means no copper or aluminum tubing. There are only three choices when it comes to brake lines—steel (usually with a tin coating to prevent rust), stainless steel (that is often polished), or nickel/copper (NiCopp) tubing that meets SAE Standard J1047 and ISO 4038, meeting all international and U.S. requirements for brake tubing. NiCopp is unique as it has the strength and structural integrity of steel lines but with the added benefit of being much more corrosion-resistant, and it bends easier.

03 This is an example of an inverted double flared brake line — This is an example of an inverted double flared brake line. The tubing is folded back onto itself to make a thick seat that is unlikely to crack. The angle of the sealing surface is 45 degrees.

There are two common misconceptions about brake lines. The first is that there is a relationship between brake line size and hydraulic pressure—not true. Pressure in the brake system is created by the master cylinder and the brake lines deliver it. Brake lines are most often 3/16 or 1/4 inch in diameter and the only difference is the amount of fluid delivered. The bigger tubing will carry more volume, so 1/4-inch line may be preferable in some instances, disc brake calipers with large piston displacements, as an example.

04 SAE-inverted flare fittings have a sealing surface that matches the 45-degree angle of the tubing — SAE-inverted flare fittings have a sealing surface that matches the 45-degree angle of the tubing. These types of fittings do not require thread sealer.

The second misconception is that stainless steel brake lines cannot be double flared. It is true that some stainless steel tubing will crack when forming double flares, however it can be done if the appropriately annealed tubing is used.

05 This is the seat in an inverted flare fitting — This is the seat in an inverted flare fitting. The combination of the nut, tapered tubing, and the seat in the fitting provide a leak-free seal.

Making Connections

The most common type of hydraulic connections found on automobiles is the SAE 45-degree double-inverted flare. That means the tubing is flared and then folded back on itself for increased strength and resistance to cracking. The tube’s flare is clamped between the nut and the seat in the fitting when screwed together so when the assembly is tightened, a leak proof metal-to-metal joint is created and no sealer or Teflon tape is necessary.

06 Found on virtually every brake system with 45-degree flares is an inverted seat to pipe thread adapter — Found on virtually every brake system with 45-degree flares is an inverted seat to pipe thread adapter. If used, sealant should only be applied to the pipe threads.

While they aren’t used on production automobiles, AN fittings are often found on hot rods and race cars. (The reference “AN” stands for Army/Navy and it’s a system that was developed by the government to ensure interchangeability and compatibility of parts made by various manufacturers.) AN fittings use tubing with 37-degree single flares with reinforcement sleeves (37-degree flares will also be found on JIC hydraulic fittings).

07 Commonly found on AN plumbing is a 37-degree-to-pipe thread adapter — Commonly found on AN plumbing is a 37-degree-to-pipe thread adapter. Again, sealant should only be used on the pipe thread portion.

The AN system uses a number to identify the various sizes of metal tubing and the corresponding fittings, and the same numbers are also assigned to the hose and their ends. Called dash numbers, they equate to 1/16 inch. As examples, -3 AN line is 3/16 inch, -8 is ½ inch.

Fittings

The common fittings used on production cars have National Pipe Threads (NPT). Pipe threads differ from fasteners and other fittings as the threads are tapered—they screw together until they tighten due to the taper. To create a leak-free seal, NPT threads often use some sort of sealer, such as Teflon tape or a leak-preventative paste.

09 An alternative to Teflon tape is thread sealing paste — An alternative to Teflon tape is thread sealing paste. This example is from ARP.

There are a variety of adapters available to connect different types of fittings—they make it possible to mix and match inverted flare, pipe, and AN fitting as well as connect standard and metric sizes.

Sealants

Compared to every other automotive product known to man, Teflon tape is likely the most often misused. Although Teflon tape can cure leaks, prevent thread galling, and protect fittings from corroding it’s often used on the wrong fittings. Teflon tape should never be used on inverted flare fittings as they are designed to seal without it. An alternative to tape is Teflon paste for fluid-tight seals.

10 Tubing cutters for steel and copper tubing come in several shapes and sizes — Tubing cutters for steel and copper tubing come in several shapes and sizes. However, these cutters will often harden so a 32-tooth-per-inch saw blade should be used. Regardless of the method, the tubing should be cut off squarely and any burrs in the end should be removed before flaring.

Brake Valves

Hot rods often have peculiar brake system needs, resulting from the configuration of the components.

11 Koul Tools offers the Surseat lapping tool that removes irregularities in 37- or 45-degree flared tubing to prevent leaks — Koul Tools offers the Surseat lapping tool that removes irregularities in 37- or 45-degree flared tubing to prevent leaks. They are available from Speedway Motors.

A typical combination would be a master cylinder mounted below the floor that is lower than the disc brake calipers. As a result, fluid will tend to drain out of the brake calipers and back into the master cylinder. The result is the brake pedal has to be pumped to bring the pads back in contact with the rotors, not a great situation in a panic stop. The cure would be a 2-pound residual pressure valve that would maintain enough pressure to prevent the brake calipers from draining and keep the pads close to the rotors, but not enough pressure to make the brakes drag. In the case of a firewall-mounted master cylinder a residual pressure valve is not normally required for disc brakes.

12 In this example the tubing is stainless steel with a single flair at 37 degrees for an AN fitting — In this example the tubing is stainless steel with a single flair at 37 degrees for an AN fitting (another application of 37-degree flares will be found on JIC hydraulic fittings).

When drum brakes are used a higher-pressure residual valve is required. Due to the strength of the return springs, a 10-pound residual valve is required to maintain sufficient line pressure to keep the wheel cylinder cups expanded. This prevents air from being drawn into the system, creating a spongy brake pedal and allowing the brakes to react quicker with a firm pedal. It should be noted that most OEM drum and disc/drum master cylinders have integral residual valves in the outlet to the drum brakes.

13 Speedway Motors offers AN brake line kits in steel, stainless steel, and NiCopp alloy — Speedway Motors offers AN brake line kits in steel, stainless steel, and NiCopp alloy. Each kit includes a 25-foot roll of tubing along with an AN adapter, weld-on brake line tabs, and braided stainless steel -AN 3 brake lines.

Brake proportioning valves are very often a part of a hot rod’s brake system. They modulate the pressure in the hydraulic system to minimize rear wheel lockup found in hard braking and to compensate for differences in braking conditions in front disc/rear drum systems. Pressure adjustments usually range from 100-1,000 psi and provide a maximum decrease of 57 percent in line pressure, which allows fine-tuning of the front-to-rear braking balance by proportionally decreasing the rear (or in some cases the front) brake line pressure. Adjustments are made by a knob with an arrow indicating the direction required to decrease line pressure. With the knob rotated all the way out (counterclockwise) there will be the maximum pressure reduction (usually around 57 percent). Rotating the knob clockwise will increase line pressure, up to 100 percent.

15 The brake line was spliced with a compression fitting (circle) — A disaster waiting to happen. The brake line was spliced with a compression fitting (circle). Compression fittings use a nut and a ferrule to seal the tubing to the main body. They should only be used on low-pressure applications, typically an oil pressure gauge.

Often found on OEM systems with disc brakes are metering valves, they don’t allow pressure to the front disc brakes until the pressure at the rear drums overcomes the brake shoe springs. At this point the valve opens to allow full pressure to the calipers. In some applications a combination valve is used that incorporates metering and proportioning functions into one valve. They often have warning light provisions to indicate if one half of a dual brake system has lost pressure.

16 Brake proportioning valves are often used to adjust front-to-rear brake bias, on the right are inline residual pressure valves — Brake proportioning valves are often used to adjust front-to-rear brake bias, on the right are inline residual pressure valves. These examples are from Speedway Motors.

Parking Brakes

At one time parking brakes were referred to as an emergency brake, for good reason in the days before reliable hydraulic brake systems. Thankfully those days are past, but unfortunately a byproduct of better brakes is that functional parking brakes are not often considered. Speaking from experience, we’ve pulled on a parking brake handle only to find out nothing that was supposed to happen happened. All cars should have a functional parking brake—a good test is that the parking brake should hold the car with the engine running and an automatic transmission in gear, or it should kill the engine with a manual transmission when the clutch is released.

17 Two-piece aftermarket disc brake rotors are common — Two-piece aftermarket disc brake rotors are common. They are usually held together with socket head screws, which should have thread lockers applied during assembly.

Breaking in Brake Pads

When installing new disc brake pads, it may take stroking the brake pedal a few times to move the pads closer to the rotor. According to Wilwood, once that is done new brake pads are best optimized by bedding in the same conditions and temperatures they are designed to operate in. A street pad can be optimized through typical street-type driving. A street pad does not need high temperatures to properly bed-in. Simply performing a series of stops that simulates street driving in a safe environment will give the pads a chance to bed-in.

18 It may be overkill but we recommend using safety wire on brake rotor fasteners — It may be overkill but we recommend using safety wire on brake rotor fasteners. Note the wire is configured to pull themselves tighter.

One Last Precaution

This is simple enough—keep brake lines away from moving parts, sharp edges, and sources of heat. Make sure they are secure by using clamps every 18 to 24 inches so they can’t move or vibrate, which can cause damage, resulting in a leak. Make sure flex lines are long enough to accommodate full suspension and compression travel and steering movement.

19 Parking brakes are often an afterthought, particularly after a rear end swap — Parking brakes are often an afterthought, particularly after a rear end swap. Lokar offers universal parking brake cables for such applications.

Follow a few simple concepts, use the proper components, and perform regular inspections and maintenance, and you’ll avoid making any brake blunders. MR