STOPPING ON A DIME
ADDING WILWOOD REAR DISC BRAKES TO A 1969 DODGE DART
Adding Wilwood rear disc brakes to a 1969 Dodge Dart
With the addition of recent performance upgrades, our 1969 Dodge Dart has the potential for speed (in mph) close to twice the speed of many U.S. highways. Refer to any physics textbook, and you’ll find the term kinetic energy, the energy of an object in motion. While traveling at the same speed, heavier objects possess more kinetic energy than lighter objects. Furthermore, faster-moving objects have more kinetic energy than slower-moving objects of the same weight. Kinetic energy doubles as the weight of an object doubles, but as the speed increases, the kinetic energy will increase by the square of the speed of the object. This means as the speed doubles, the kinetic energy quadruples. With speed, there’s a greater amount of kinetic energy the braking system must convert to another form of energy (usually heat) to stop the vehicle. To keep up with the increasing speeds, the Dart’s powerassisted four-wheel drum brakes gave way to 1973 manual factory front discs, and eventually, a complete Wilwood front disc brake kit was installed in 2002. With
the latest increase in speed and wanting to take advantage of the benefits of disc brakes (self-adjusting, ease of inspection, better cooling, fade resistance, freedom from pull, and self-cleaning), we contacted Wilwood Engineering about a pair of rear disc brakes to complement the front disc brakes. The reps at Wilwood suggested a pair of fixed calipers and matching rotors with a universal park brake kit.
Before we could order the brake components, Wilwood required several measurements to confirm a proper fit of a Wilwood kit for our application. It was proposed that we use a 12.19-inch rotor with our 15x7 Weld wheels. Several illustrations (easily found on Wilwood’s website) provided the exact measurements that Wilwood required to provide an interferencefree assembly for our Dart. We made measurements of the axle flange to axlehousing flange along with rotor and caliper fitment checks inside the hoop of the Weld wheel. We made the measurements with machinist rules, depth micrometers, and even mocked-up cardboard cutouts as additional clearance checks to guarantee the proper fit of the disc brakes. The measuring took some time, but the effort would be worth it if we ordered parts that fit properly. Whenever there’s any doubt about the fitment of the parts, Wilwood has plenty of helpful representatives to provide assistance.
The measurements confirmed that a pair 12.19-inch rotors (PN 160-7508) would fit on our Dart with a 2.36-inch axle offset. We selected a complete kit (PN 1407144), including two four-piston calipers (PN 120-13839-BK), pads (PN 150-8850K), and bracket kit (PN 2497116/17) — backing plate and drum park brake assembly. Additional parts in the kit were the caliper bolts, shims, and cotter pins. We selected 2.33-inch rotor registration ring adapters for the axle hub and tube adapters to fit the factory (hard) brake lines to the new calipers. Lastly, we elected to keep the park brake operational, so we selected the Wilwood universal park brake cable kit (PN 330-9371).
Before our brake kit arrived, we performed some preliminary work. We had been running the famous “Green” bearings for years, but these bearings had the pressed flange (aka the Mopar Performance Green bearing, PN RP400), which wouldn’t work with the Wilwood kit. Rather, the snap ring style, loose flange (aka the Strange/moser Green bearing, PN MO400) was required. To swap the bearings, we pulled each axle from the 8¾-inch, used a hydraulic press to push the Mopar Performance bearings off the axles, and pressed on the Moser Green bearings. We omitted the installation of the loose flange that came with the Moser
Green bearing, because Wilwood provides their required flange with the kit.
The disc brake installation got underway by disconnecting the driver-side drum park brake cable from the front park brake cable adjuster, unthreading and capping the brake line from the wheel cylinder, and removing the entire drum brake assembly from the axlehousing. We slid the backing plate onto the axle after removing the snap ring from the new Moser bearing, and with the plate located, the snap ring was reinstalled. The axle assembly was slipped into the axlehousing, and the backing plate was lined up with the five axlehousing flange studs. Finally, we attempted to slip the bearing retainer into place when we noticed the axle flange was making contact with the outermost return spring on the drum park brake. After many attempts, there was no adjustment that didn’t result in contact between the spring and axle flange. It turned out that the aftermarket Moser axles we had installed in 1990 had extremely beefy flanges and the screwin wheel studs interfered with the return spring. A call to Wilwood provided us with the fix. The spring could be removed without any reduced park brake performance.
With the spring removed, we installed the backing plate and axle. A second challenge resulting from the Moser axle was the installation of the bearing retainer (loose flange). A factory axle has an access hole in the axle flange to allow the bearing retainer nuts to be torqued into place. Our Moser axles didn’t have this access hole, so we had to use a thin-line openend wrench to tighten all five of the nuts. Neither this concern nor the park brake spring were the fault of Wilwood or Moser, but rather the domino effect of one mod influencing another mod. The Moser axles worked for 28 years with the drums, and the Wilwood brakes would’ve installed without any difficulty on factory axles (or aftermarket axles with an access hole), but in our case, it took more effort and time to make them work together.
The hub register ring was installed on the axle flange hub to center the rotor onto the axle. We slipped the rotor onto the wheel studs and over the register ring, and the calipers were installed onto the backing
plate. We followed Wilwood’s recommendation of installing two shims between the caliper mounting ear and the backing plate clinch nut. The two shims were a starting point in an attempt to center the fixed caliper over the rotor; however, we ended up requiring an additional shim on each bolt. We removed the caliper and the rotor and reinstalled the caliper without the rotor. With the number of shims determined to center the caliper, we needed to establish the correct depth of the caliper bolts in the backing plate’s clinch nuts. The end of each caliper bolt needed to be flush with the end of the clinch nut. Shims were installed between the head of the bolt and the caliper-mounting ear to establish the flush fit that was desired. Each caliper bolt (on the driver rear) required one shim between the caliper bolt head and the caliper mounting ear to establish the correct bolt depth, and each bolt required three shims between the caliper mounting ear and the backing plate’s clinch nuts to center the caliper over the rotor. It’s imperative to use an equal sum of shims on each bolt on an individual caliper. After determining the necessary shims, the caliper was removed.
One last time, we fitted the rotor followed by the installation of the caliper. We applied a dab of red thread locker to each properly shimmed caliper bolt, and then torqued each bolt to 40 ft-lb. Both brake pads were slipped into the caliper, and a large cotter pin was pushed through the caliper body and each pad’s backing plate to hold the pads in place. With the caliper installed, a tube adapter was threaded into the caliper followed by the factory hydraulic brake line being threaded into the adapter. While Wilwood offers various flexible brake lines, we elected to use rigid brake lines to the caliper, so the factory brake line had to be manipulated (carefully bent) to move the end of the brake line to the tube adapter inlet housed in the caliper. If the brake lines were suspect, new brake lines should’ve been run, and those lines could be bent as needed.
With the brake assembly on the left rear completed, we repeated the same procedures on the right rear. Wilwood offers Hitemp brake fluid, but we used a new bottle of DOT 4 brake fluid (DOT 3 or DOT 5.1 are also acceptable). Wilwood doesn’t recommend using DOT 5 Silicone brake fluid for performance driving. Regardless of how the brakes are bled (gravity, pressure, or vacuum), the goal is to bleed each
caliper of any trapped air. Four bleeder screws are on each caliper, but only the top two (one on each side of the rotor) are used to bleed air from the brake caliper. We found a gentle tap on the caliper body with a soft mallet aided in freeing any air bubbles that may have stuck to the machined surfaces in the caliper body. After bleeding the system, the brake pedal felt firm and very similar to the previous disc/drum setup.
The last step in our upgrade was to install the universal park brake kit on the Dart. We trimmed the cables and sheathing to the required length, and we used the supplied hardware to attach the sheathing to the backing plate and the cable to the park brake lever at the top of the backing plate. The factory-installed clips on the axlehousing and mounting points on the chassis routed the cables in a similar manner as the factory. We ended up modifying the cable clamp from the kit and slipping it over the threaded end of the factory park brake cable that extended from the front of the car. The cable layout is clearly covered in the photos.
Wilwood has a very specific procedure for bedding the pads to the rotor, and after observing the bedding methods, the rear discs have provided excellent braking performance. We don’t have access to a skidpad, but at Beaver Springs Dragway, the brakes hustle down the Dart to make the first turn off after a quarter-mile run, which was never a consideration with the drum brakes.
The drum-to-disc conversion required a full weekend to complete, but the results have been excellent. A hydraulic press may be necessary, but the rest of the installation can be performed with handtools. A vehicle lift would be nice to use, but jackstands will suffice. The keys to the disc installation are accurately measuring every parameter Wilwood requires, following the installation instructions, and if a problem arises contacting a Wilwood representative for advice and direction. Respecting these three keys will provide a straightforward Wilwood disc brake installation, followed by years of repeatable, trouble-free stopping power for your Mopar.
The rear drum brakes have served without any problems for the last 28 years. The duo-servo drum brakes offer great stopping power and provide outstanding park brake performance. As the Dart’s mph output has increased, it was time to upgrade our trusty drum brakes with rear disc brakes to take advantage of the benefits that discs can provide.
The 10-inch drums were originally drilled for the 5 on 4-inch small bolt pattern. The author re-drilled (with an electric hand drill) the drums for the 5 on 4.5-inch big-bolt pattern when the Moser axles were purchased in 1990. The big bolt pattern was desired because of the brawnier axle flange and greater wheel selection options.
Wilwood suggested a 12.19-inch rotor to fit inside our 15x7 Weld wheel. Measurements were made based upon Wilwood’s illustrations found on their website. Machinist rules, depth micrometers, and even cardboard mockups were made to guarantee the rotor and caliper would fit without interference. When the rotors and calipers arrived, the measurements proved accurate, and the rotor and caliper fit in the wheel without any impediment.
The axle flange hub had to be measured for the correct register ring. The measurement was just under 2.30 inches. Wilwood offers many different-sized rings, and the 2.33-inch register ring was the closest to our hub, so one for each axle was selected.
With all five axle flange nuts removed, the axle was slipped from the 8¾-inch axlehousing. When removing the axle from the housing, support the axle flange with one hand and pull the axle gently, while extending the other hand down the axle. Be ready for the axle weight, as the axle is fairly heavy. Once the axle is free from the axle seal in the housing, the axle can be set aside. The bearings are aftermarket Mopar Performance “Green” bearings.
The top left bearing is the Mopar Performance-style bearing that was pressed off the axle. It has a fixed flange. The top right bearing is a Moser-style bearing that was the required replacement bearing. The bottom right was the loose flange that was omitted during the installation. Wilwood provides their required flange with the kit.
The “Green” bearings used on the Dart have the pressed flange (aka the Mopar Performance Green bearing, PN RP400) that wouldn’t work with the Wilwood kit. The snap ring style, loose flange (aka the Strange/moser Green bearing, PN MO400) was required.
When the Moser axles were installed in 1990, the axle flange didn’t have an access hole as a factory axle would have. While inconvenient, for all these years, an open 9/16-inch wrench has been used to remove the five bearing retainer nuts. The lack of the access hole became a big concern during the installation of the Wilwood disc brake kit.
The use of a hydraulic press is necessary for all of the bearing pressing. When pressing the bearing on to the axle, all the hydraulic pressure must be provided through the collar and the hub of the axle. Press slowly and deliberately, and if anything hangs up forcing the hydraulic pressure to rise greatly, stop pressing and resolve the concern before continuing.
With the brake line removed and capped and the rear park brake cable loosened from the front park brake cable, the fully assembled drum brake assembly was removed from the rear end housing. The assembly will still operate if needed (on another vehicle), so it was wrapped and stored for future use.
The axle with the disc brake backing plate slid into the rear axlehousing. The backing plate had to engage with the five bearing support studs on the rear end housing. The small shoes on the backing plate act as a drum brake for the park brake application for the Wilwood kit.
The loose bearing flange snap ring was removed. This allowed the backing plate, with the one park brake spring removed, to slide onto the axle and bearing. Once the backing plate was installed, the snap ring was reinstalled in its groove on the bearing.
When the backing plate was installed onto the Moser axle, the front side park brake drum return spring made contact with the much beefier, when compared to the factory’s axle, flange and the aftermarket screw-in studs. The fix was to remove the single spring, which left only one spring on the park brake. The performance of the park brake wasn’t affected by the removal of the spring.
The entire Wilwood kit included a pair of backing plates, rotors, four-piston calipers, two bearing retainers, register rings, a universal park brake cable, and all the hardware to mount the components to the Dart. Plenty of instruction material was included with the kit. Take the time to read all the instructions before jumping into the disc brake installation. This will allow the installation to progress smoothly.
The supplied bearing retainer flange had to be slipped onto the five bearing support studs on the rear end housing, so the nuts could be installed. The fit was tight due to the substantial heft of the axle and the screw-in studs. The retainer was wiggled into place followed by some wrestling to get the nuts threaded into place. This took some time, and when it came to tightening the nuts, a slim-line open end wrench was the only option. If the axle flange had included the access hole, the entire ordeal with the flange nuts would’ve been negated.
The register ring was slipped onto the axle hub with the step on the outer circumference facing outward. The rotor was pushed onto the axle studs, and the reference ring’s step engaged with a matching step on the rotor’s hat. The register ring centers the rotor without relying upon the axle studs.
A pad was slipped between the caliper pistons and each side of the rotor. A large cotter pin was pushed through an access hole on the caliper, a hole in each pad’s backing plate, and then through another access hole on the inboard side of the caliper. The cotter pin was bent and trimmed so it wouldn’t contact the wheel.
The single shim between the caliper bolt head and the caliper ear ensured the caliper bolt didn’t extend beyond the end of the clinch nut in the backing plate. Wilwood requires the bolt end to be flush. If the bolt extends out too far, the bolt may contact the rotor, so shims are required. If the bolt doesn’t reach the end of the clinch nut, shims must be removed to ensure full bolt thread engagement to secure the caliper.
A final check of the caliper location confirmed that it was properly centered over the rotor. With the caliper properly centered, the caliper bolts were dabbed with red thread locker, threaded into the backing plate, and each bolt was torqued to 40 ft-lb.
To center the caliper over the rotor, three shims were required on the caliper bolt between the caliper ear and the backing plate. Another shim was necessary between the caliper bolt head and the caliper ear to properly locate the caliper bolt’s depth in the backing plate.