The braking system is one of the most critical areas of vehicle performance regardless of the level of restoration. The car must have a properly operating brake system for safety and performance. The standard braking systems that came with early Mustangs were able to stop the cars, if only just adequately by today’s standards. Few things can ruin the pleasure of driving an otherwise well-sorted-out car than a faulty or underperforming braking system. Despite numerous upgrades in both technology and materials since these cars were new, I do not cover the extensive upgrades to build a brake system for a typical restomod or pro-touring type of vehicle. I do introduce a few upgrades using Ford factory parts that greatly improve braking on a typical early Mustang, while also enhancing reliability/ durability and maintaining the originality of these cars.
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These modifications should be applicable and cost effective for daily-driver or weekend-cruiser projects. They provide overall performance superior to the stock setup, making more frequent use of the car possible. The steps for the front brakes can also be applicable to a show car, with the exception of the rear brakes because it involves too visual a change. In this chapter, I mostly address the primary components of the braking system at the wheels. I briefly discuss other items, such as the master cylinder, power brake booster, and brake lines. Always consult the factory service manual for specific information on tightening torques, detailed assembly procedures, etc. I only provide some guidelines for what to watch for and how to best resolve any issues.
Usually, it is more cost effective to replace components than to rebuild them. With a show car, this may not be true if higher judge’s scores for originality is a priority. The extra expense of machining and/or rebuilding are then more practical. Fortunately, many newer replacement parts can still be used for a show car because they are visually similar to the original parts. I point out some instances where this may be possible, and where only original parts will do.
Initial Inspection and Evaluation
Brakes wear as a normal consequence of use, so evaluating the braking system primarily involves trying to determine if there is excessive wear, damage, or leakage.
For disc brake systems, deep grooves in the surface of the rotor are evidence of excessive wear and/or damage. A normal rotor surface should be flat with only very fine surface imperfections that can barely be felt by running a fingernail across them. It should turn smoothly with no interruptions or sticking. Any significant grooving means the rotor has to be remachined (if there is enough material/thickness left) or be replaced. Also check for discolored and/or cracked rotor surfaces (a sign of overheating) and warping. The latter is not always visible but can often be felt by turning the rotor on the hub and experiencing intermittent sticking or drag, or a pulsating feel through the pedal. If any of these symptoms are observed, the choice is between remachining (turning) and replacement.
Inspect the seals around the pistons in each caliper for leaks. If there are none it is probably possible to simply clean and/or paint the caliper before reusing it. Always use a new hardware kit (clips, rubber parts, etc.). Check the rubber of the brake hoses for any excessive cracking or signs of leakage. Replace the hoses if there are any signs of leakage whatsoever. If the hoses are reused, it is a good idea to clean them and wipe them down with a silicone protectant.
Last, since the front wheel bearings and grease seals are replaced as a matter of course, it’s only necessary to ensure there is no corrosion at either the bearing pocket in the rotor or on the steering knuckle where the bearing makes contact. If there is substantial rust on these parts, they must be replaced.
Drum brake systems are a bit more complicated to evaluate because they must be disassembled to a greater degree before they can be fully inspected. One of the first telltale signs of a problem is fluid on the backing plate. This is a sign that a wheel cylinder likely needs to be replaced. These are generally easy to find and are inexpensive, so this is no big deal.
The drum is often difficult to remove and is an important indicator of potential problems, such as a high degree of wear. As this wear occurs, a step that tends to grab the edge of the brake shoes is formed, and thus prevents the removal of the drum. Loosening the brake shoes via the adjuster wheel and a few evenly spaced, soft-faced mallet blows to the outside of the drum often helps remove it.
After the drum is off, measure to determine if the drum pad material exceeds its minimum thickness specification. If so, it can then be turned to remove any ridge that may have been present, and also to restore a smooth braking surface. If there are no signs of leakage from the wheel cylinder, this part can be reused, but replacing it means a longer service life, especially if it’s the original part. Materials technology for seals, etc., has greatly improved in the last 40 years; newer materials are compatible with most modern brake fluids, including synthetics and synthetic blends. Most of the remaining hardware on the backing plate can be reused after cleaning, assuming there has not been any excessive wear at the points of contact sliding, etc. It is generally a good idea to replace the springs because they tend to weaken over time as a result of fatigue and heat cycling.
New parts for most of the drum brake hardware, except for the pivot arm, the bridge, and the backing plate itself, are available if needed. Even the backing plates can be reconditioned and/or welded to return them to spec if they prove to be hard to find.
The rest of the braking system consists of the master cylinder, power brake booster/diaphragm (if so equipped), hydraulic lines, and pedal assembly. These items can usually be reused after a cleanup if there are no signs of leakage (fluid or vacuum) and the brakes were working properly.
The master cylinder can be rebuilt with new seals, etc., but, unless you rebuild it yourself, it’s often less expensive to simply replace. With a show car, the original master cylinder should be retained but for a daily driver or a weekend cruiser, it is often more practical to simply replace the master cylinder rather than have it rebuilt. The power-brake booster can likewise be rebuilt, but it’s also only practical for show-car authenticity.
The brake lines can almost always be reused unless they are damaged or corroded. For those who would like to make an upgrade from the factory galvanized mild-steel lines, it’s often possible to get direct-fit lines made in stainless steel from companies such as Classic Tube of Lancaster, New York. These lines not only look better than the factory lines, but they also last almost indefinitely, even in cold climates where the roads are salted. This upgrade may not be suitable for show-car authenticity, but it clearly offers a significant and inexpensive benefit for most daily drivers and weekend cruisers.
For the pedal assembly, there is little to do other than possibly replace the rubber pads and maybe a bushing or two if any are worn. For almost all restorations, the pedal assembly is just cleaned, lubed, adjusted, and retained as is.
The parking-brake system is also generally just cleaned, lubed, adjusted, and reused as is. Worn or damaged components might require replacement. “Wear” can also include stretched braided-steel cables; they become too long to allow full engagement of the parking brake. If this cannot be resolved by adjustment, buy a replacement cable(s). We had to do this anyway because we converted the rear brakes from drums to discs, but this is common even when the factory parts are retained. These cables are usually easy to find and don’t cost much, but there really is no need to replace them unless they’ve stretched or are otherwise not usable. As with the service brakes, the pedal (or handle) for the parking-brake system generally needs little attention other than cleaning, lubing, and possibly adjustment in most instances. Replacement parts are usually easy to find.
Disc Brake Conversion Step by Step
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #1
After the studs have been pressed into the axle, install the correct-dimension centering ring around the hub to help center the rotor to the axle centerline. This is critical and prevents misalignment, which could create unwanted vibration and/or poor braking performance. Note how the centering ring has a small lip at the lower edge; this must be located next to the axle. The chamfered edge must be at top.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #2
When assembled with the rotor, the centering ring locates the rotor concentrically with the axle centerline. It also can serve as a pilot for the wheel if it has the correct diameter hub bore. Conversely, the wheel hub bore must be large enough to clear the centering ring or else the wheel won’t sit flat on the rotor hat—a potentially dangerous situation. This view also shows how the raised shoulders on the longer studs act to pilot the rotor hat in combination with the centering ring. The locating ring does the final centering while the studs merely help guide the rotor onto the ring. Since factory wheels from this era are “lug-centric,” the presence of the raised center ring shouldn’t be a factor. The lugs position the wheel and tire. However, if newer hub-centric wheels are to be used, then the dimensions of the centering ring and the wheel’s hub bore must be properly matched.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #3
The caliper mounting plate must be installed over the axle, in the direction shown, before the axle bearing is pressed on. When pressing on the axle bearing, a film of thread locker should be spread over the bearing surface of the axle before the bearing is pressed onto it with a hydraulic press. Once the bearing has been pressed on, it cannot be reused because the inner bearing race has lost material as a result of the interference fit with the axle. After the bearing is pressed on, any such residue as well as any excess thread locker must be wiped off. A thin film of grease should be applied to the area where the axle housing seal contacts the axle to ensure it has proper lubrication when the axle is turned.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #4
Ford used different size axle bearings according to the vehicle application, which can be determined by the appearance of the axle housing ends. Our housing had the smaller size bearings, which is consistent with most Mustangs. Heavier and/or higher-performance cars usually came with the larger bearing housings, which would have a more pronounced step up from the axle tube to the bearing seat. Because the backing plate holes were in the same place, it required different size heads on the backing plate bolts. The larger-headed bolt (left) is the correct one to use with smaller bearing axle housings like ours. The smaller headed bolt (right) is correct for use with axles equipped with the larger bearings.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #5
The former mounting plate bolts attach to the mounting plate as shown. Insert the correct socket through the hole in the axle flange, which is drilled specifically for this purpose, and torque these bolts down. No gasket is required between the mounting plate and the axle housing because the axle seals perform the needed sealing function. Do not overtighten these bolts because it could warp the mounting bracket and misalign the caliper. At a minimum, this would cause uneven brake wear with the potential for even more severe problems. In some cases, the mounting bracket holes may need to be redrilled to rotate the calipers such that they clear the spring; this cannot be determined until all the parts are assembled.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #6
When the caliper is installed on the mounting bracket, you can see how much space the package occupies. The rotors sit inward from the axle flange and toward the differential. This provides extra clearance to the wheel in the lateral direction. Note how the caliper mounting bracket and bolts neatly tuck behind the rotor to allow this. The low profile of the caliper is in part due to the type of parking brake mechanism, which moves most of the mechanism inward over the axle tube. This frees space within the wheel and provides the radial clearance to allow the use of 18-inch wheels. The caliper mounting bolts should always be coated with a high strength thread locker to ensure they do not vibrate loose. Since only two mounting bolts are used and they are not especially large, this is especially critical. The correct bolts and locking washers are included in the Currie kit, but the use of a thread locker provides a bit of extra insurance for even more safety.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #7
The Currie Enterprises disc-brake conversion kit includes new brake hoses, which are required for the new brakes. These hoses each feature a protective sleeve to prevent chafing or other potential damage. The hose attachment to the calipers is common, but a little creativity is required for the connection to the opposing rear brake and the incoming pressure line from the car. Before we can address that, however, we must first secure each hose to the housing by securing the loose end with a tab.
MUSTANG RESTORATION: DISC BRAKE CONVERSION- STEP #8
Position the mounting tab so that the hose is not stressed, yet it is still protected from road debris, exhaust heat, etc. The area where the original factory brake line was located is a good place to use, if possible. Here, we see the hose end reaches the factory line location, yet still has space for the incoming hard line, which comes from the vent tube area. The factory tab needs to be ground off.
When installed, the new hose mounting tab is located the same basic area where the factory hard line was mounted. The new hose is protected and in an unstressed position. The axle tube vent is used to help secure the distribution block that ties the two rear brakes and the incoming pressure line together. Basically, we use Ford factory parts to retain the factory appearance while still gaining functionality for our upgrade.
Front Brakes: Installation
Our car came with single-piston front disc brakes, which we felt sufficient for our intended use. These brakes are reasonably effective for typical street driving, but they were not suitable for highperformance driving (I address that later in this chapter). As noted earlier, it generally is more practical to replace the original factory parts than it is to rebuild them, unless you are building a show car. So we simply disassembled the front brakes, cleaned the parts we reused, and bought new replacement parts for the rest. Even though our rotors were in pretty good shape (they didn’t even need to be cut), we decided to go with new ones for the smoother friction surfaces and the improved metallurgy in modern discs. Their design is slightly different than the factory parts. The new rotors also were slightly lighter than the originals; a minor performance benefit, in our particular case. We installed new bearings in the rotors and also new hardware for the calipers. All of these components were direct-replacement items, and thus go in exactly the same way as the original factory parts.
For brake pads, we selected a premium ceramic-based compound, which would not only perform better and last longer than the original factory compound, but should create significantly less brake dust. Make sure you adjust the wheel bearings correctly per the factory service manual. When using new direct-replacement parts instead of rebuilt or refurbished originals, there really is no difference beyond the benefits gained from the newer materials and technology. Just be sure to use good-quality grease on the bearings and keep it and any other contaminants off the friction surfaces. Also spray the rotors with brake cleaner and wipe them down with a lint-free cloth before you install the wheels and tires over them.
For those who may wish to upgrade front brakes to a higher level of performance, numerous aftermarket options are available, from mild to wild. (I do not cover the typical restomod options, other than to say the aftermarket offers very significant gains in braking performance.) Many are very reasonably priced yet still more expensive than the simple direct-replacement approach I’ve shown.
Another option for those who want substantially improved braking performance while retaining a more factory look is to install the factory four-piston front calipers that were optional on various models. These can be installed with minimal effort, although other components besides the calipers need to the changed as well. All of the needed parts are generally available from the various companies that specialize in Mustang restorations, and the total can often be less than the aftermarket alternatives. These don’t match the performance of most of the aftermarket systems, but are a vast improvement over the factory single-piston caliper option or a front drum-brake system. They can also be used in many forms of mild high-performance driving while providing a factory-correct appearance that no aftermarket brake kit can. For ultimate braking performance, aftermarket kits are the only way to go. However, for a weekend cruiser where improved braking performance with a factory look is desired, this is a very viable alternative.
Rear Brakes: Conversion and Installation
While we were content to retain the factory brake setup in the front, we did not feel the rear drums that came with our car would handle the more-frequent driving schedule we had in mind. Drum brakes are less efficient in wet weather than discs and tend to be much more sensitive to adjustment. Discs are, by design, inherently more self-adjusting as they wear. You don’t see many race cars with drum brakes. Discs are also far simpler and easy to service as well as lighter and more effective. There were many good reasons to convert our rear drum brake system to a disc brake system.
We wanted to retain a factory appearance, however, so our options became much more limited. There are numerous aftermarket options available for the rear brakes as well, and though our stock GT-style wheels hid the brakes well, we did not want to go this route, mainly for aesthetic reasons. We also really didn’t need the ultimate in braking capability for this vehicle. We simply wanted to benefit from the advantages of a modern disc-brake system.
We found an alternative from Currie Enterprises in Anaheim, California. It offers a rear disc-brake conversion from a 1991–1993 Ford Thunderbird SC for 9-inch axle assemblies. This not only provides the factory look (albeit a newer factory look) we desired, but it also allows us to still use our original wheels and not have to worry about trying to find special parts when we need to service the brakes. Unlike many of the aftermarket brake upgrade kits, the Currie kit clears 14-inch wheels and does not require any axle modification beyond simply installing the unique mounting brackets for a given application. Other than adapting the parking-brake cables, this really is a cost effective, true bolt-in system.
Compared to using the rear disc brakes from other, newer Ford vehicles (Lincoln Versailles, for example), these are not only more effective and much easier to find, but they also use a common pad that is available in various compounds to better suit your intended use. We went with a premium ceramic-based pad, as with the front brakes. If you don’t want to change the original look of the car, this upgrade is clearly not for you. While it may not be necessary for a daily driver either, it clearly would be a benefit in that case and with a weekend cruiser such as ours.
The only other option for retaining a true early look and higher performance is to upgrade to some of the very rare factory rear-disc-brake setups. The parts for these are difficult to find (unlike the four-piston front caliper option) and very expensive. They also don’t offer the performance and serviceability benefits of the Currie system either. Simply put, if you are going to upgrade the rear brakes of your early Mustang and don’t need the highest performance or want the non-factory look of an aftermarket kit, you really can’t do any better than the Currie solution. It provides better performance, reliability, and serviceability, along with the ability to still use most original factory wheels in a cost-effective and Fordfactory- appearing manner.
Because we upgraded our rear brakes, we also have to make some adaptations to the brake hoses, lines, and parking-brake cables. To finish, I show what needed to be done relative to our rear brake hoses and lines. On a vehicle where the brakes have been kept original these steps would not be necessary; just clean the lines and fittings prior to final assembly.
Written by Frank Bohanan and Republished with Permission of CarTech Inc