Tech Install: Upgrading Front Drum Brakes With Factory Disc Parts

Cars back in the ’50s and ’60s seemed to do well with their four-wheel drum brakes. Of course, back then just about everyone had drum brakes on their cars, and they drove with a certain sense of knowing that stopping wasn’t going to be done on a dime. These days, many factory cars come equipped with four-wheel disc brakes and that puts our classic cars at a slight disadvantage out on the open road.

We’ve already upgraded this Mopar with a modern EFI system from FAST, we upgraded the handling with front and rear sway bars from Hellwig Products, and we installed Moser Engineering alloy axles with a Detroit Truetrac limited slip from Eaton Performance. But we wanted more out of this ’65 Belvedere when it comes to stopping power, because one panic stop with drum brakes and you’ll soon realize what that disadvantage is.

A typical big-brake kit, like this one from Master Power, is a bolt-on kit that requires 17-inch wheels.

Most brake upgrades, be it two-wheel or four-wheel, can be bolted up to your existing spindles and axle, respectively. They look great and perform even better, and it’s a common upgrade to many musclecars. Some of the kits available can be used with the 15-inch factory steel wheels if you want, or you can go to much bigger rotors if you’re willing to upgrade to 17-inch or larger wheels. That’s where a big-brake upgrade can turn into a much bigger project, because you not only have to decide on what calipers and rotors you want, but then you have to pick out a wheel and tire combination and that can quickly exceed your budget.

But what if you’re on a budget and you don’t want to replace the wheels and tires?  Options from Master Power, SSBC, Baer Brakes, and others offer brake packages to tuck under your 15-inch steelies and are a great option for quality brakes, but what if you’re really pinching your pennies? Well, you’re in luck because there are alternatives that can improve your braking with factory parts from a disc brake donor car, and we did such an upgrade on our ’65 Plymouth.

The 1962 to 1965 Mopars came with either manual or power four-wheel drum brakes, but some later Mopars make great donor cars for a factory-style disc brake upgrade. We’re going to shed some light here on this upgrade and give you some pointers on what worked for us on our 1965 B-Body Mopar.

Disc Brake Parts And Donor Cars

While many aftermarket companies make adapters to mount their calipers, we are using factory parts without adapters, so we had to source our parts from another vehicle. You can buy complete kits from companies that provide you with new factory parts like spindles, rotors, bearings, calipers, and caliper brackets, and they can also include a new master cylinder, proportioning valve, and brake hoses.

Some kits include provisions to mount a GM master cylinder and booster, but we opted to use all Mopar parts on our Belevedere.

But many of those kits, like the one we initially bought, include a GM master cylinder with a bulky adapter that mounts the GM master cylinder to the Mopar brake booster. We wanted to keep everything Mopar, so we got a replacement master cylinder from Rock Auto, and an adjustable proportioning valve from Summit Racing to complete our disc brake upgrade.

The spindles that we bought are found on ’70-’74 E-Body Mopars, or the ’73-’76 A-Body Mopars, like the Valiant, Dart, Duster and Demon. The spindles are not parts that wear out, so if you want to scrounge the local yards for these parts you can save a little bit of coin – but be sure to get the caliper brackets, at the very least, because you probably won’t find them through auto parts stores. Otherwise, you can find the whole kit from online sources by searching for brake upgrades.

We used the A-Body spindles because that’s what we’ve read works best. There are some sources that claim you can use the taller, later B/F/J/M/R-Body spindles, but some say that this affects the suspension geometry, and that was enough to convince us to stick with the A-Body spindles.

All of these parts are found on disc brake-equipped A-Body Mopars from the early '70s.

When it comes to the rotors, there are a couple size options: the 11-inch and the 11.75-inch HD rotors found on ’76-’79 B-bodies and ’79-’81 R-bodies. If you want to retain your 14-inch wheels, you need to stick to the 11-inch rotors; while the 11.75-inch rotors will require 15-inch wheels. The caliper mounting brackets are also different, based on the rotor size, so you’ll need to get the proper mounting brackets for the calipers if you’re getting your parts from the wrecking yards.

The caliper types differ as well, there are pin-type calipers, and slider-type calipers. The pins are hard to come by, and through our research we decided on the slider-type calipers because of ease of installation and readily available parts. Loaded calipers (pads included) can be bought at many auto parts stores, as well as the rotors and bearings. Caliper brackets are harder to find and are included in a complete conversion kit like ours.

Brake Upgrade Installation

Safety first: ALWAYS use jack stands to support your vehicle.

Our kit included 11-inch rotors, spindles, calipers, caliper brackets, hoses, hardware and bearings, and the GM master cylinder and adapter that we discarded. We decided to put a coat of paint on our parts since they were brand new and clean, it helps protect surfaces and also looks pretty cool, too. We used high temp paint for the parts, and caliper paint for the calipers.

After laying out all the parts, and doing some test fitting to make sure there wouldn’t be any interference with the 15-inch police rally wheels on our Belvedere, we went to work with our upgrade. We want to remind you to support your car on jack stands whenever you are removing the wheels, and especially if you’re crawling underneath the car to do any type of work. The time it takes to put jack stands in place is minimal compared to the time it takes to crawl out from having a car fall on top of you – if you don’t get crushed in the process.

With the brake drum removed, we had a little better access to the backing plate. The drum slides off fairly easy, but the backing plate and spindle is where you’ll have to work a little harder. The steering arm contains the lower ball joint, and it bolts to the backing plate with two bolts, while two more bolts attach the backing plate to the spindle.

Removing the backing plate assembly can be done, but access to the steering arm bolts is limited, and both parts are discarded so it wasn't necessary to separate them.

Since we were replacing both the upper and lower ball joints and discarding the original spindle and backing plate, we didn’t bother removing the steering arm from the spindle or backing plate, and removed them as an assembly. A few hard hits with a 5-lb. sledge did the trick and the ball joints were loose. This allowed us to remove the spindle and gave us access to the upper ball joint.

We purchased new upper and lower ball joints from Rock Auto because we knew the old ones were shot; it just makes sense to replace ball joints when you’re doing an upgrade like this, and when the spindles are being replaced. The lower ball joint is a stock replacement for the ’65 Belvedere, and it bolts on to the new spindle without modification.

A special tool is required for the upper ball joint, we used a metric socket and fought with it. Next time we will rent the tool, or buy it, to avoid the troubles.

The upper ball joint is threaded into the upper control arm, and there is a special tool for removing it. We couldn’t find it locally, but used a large metric socket with our 3/4-inch drive and went to work on it. In retrospect, the $45 tool might have made the ball joint removal easier, and you can possibly rent it from a local auto parts store.

We used the floor jack handle for leverage, and it was tough but the upper ball joint came out with some persuasion. It has normal threads, so if it feels like it’s not moving, don’t give in and try to turn it the opposite direction. The new upper ball joints were tight, but that’s a good thing.

With both ball joints in place, the spindle is installed with the caliper bracket to the rear, which doesn’t pose a problem. The spindle can mount to either side, with caliper placement dictating which side to mount the spindle. The lower steering arm is bolted to the new spindle and two cotter pins are supplied with the lower ball joint. Be sure to have extra cotter pins on hand, you’ll need about six per side total, including the cotter pins provided with the ball joints.

The races were already pressed into the rotors that we bought, and the included bearings were well greased up before rotor installation. When tightening the spindle nut, one method that works is to tighten the nut until there is a lot of resistance when trying to spin the rotor. Don’t over-tighten it, but just enough until it becomes tough to rotate and then back off on the nut a little by moving the wrench from one lug stud to the next one counter-clockwise, and then install the crown-nut and the cotter pin. The caliper and brake hose were installed, and the tie rod end was reconnected to the steering arm, completing the upgrade to the suspension end of the install.

We mounted the caliper to the rear for clearance of our Hellwig sway bar up front. Brake hose routing was not an issue for this car, though for some E-Body brake upgrades it might be.

Master Cylinder Installation

When it comes to the master cylinder, you absolutely want to replace the single reservoir with a dual-reservoir for a disc brake swap. We searched the online upgrade sites and there were no real answers as to what part number to get. A wise choice is to get a master cylinder that matches the parts you’re putting on the car, you can’t go wrong there.

You can even use the later, aluminum master cylinder with the plastic reservoir with an adapter to mount it to the four bolts on your booster or firewall; or you can install a master cylinder from a ’73-’76 A-Body like the one that we bought new for about $39.

Installation is pretty straight forward, removing the original single reservoir and bolting the new master cylinder into place on the booster or firewall. The spacer and seal that was between the old master cylinder and booster remained in place, and the stock pushrod was retained.

Left: Prior to putting fluid in the reservoir, mount the master cylinder and form all of your brake lines first. Later, when you add fluid the lines will be ready to connect. Right: Bench bleeding the easy way. Phoenix Systems brake bleeder kit simplifies the process with adapters included their kit.

We had to get some new adapters and brake lines to convert from the single outlet to the dual outlet, and a quick trip to the local auto parts store netted us with everything we needed. It’s best to draw out what you’re planning on doing, and to bring old parts and the new master cylinder with you for this task. Looking at the master cylinder reservoirs you can tell which is for the calipers by the capacity: the one to the rear is much bigger and holds more fluid.

We found a couple short brake lines and the appropriate adapters at the parts store, and matched everything up while we were there, saving us a second trip. About $26 later we were on our way back to the house to finish up the brake install and to bleed the brakes.

We bent all of our brake lines, and made all of our connections before we filled the reservoir to bench bleed it. This made sense since we were going to be dealing with a lot of brake fluid dripping if we didn’t have the lines already planned out ahead of time.

There are a few ways that you can bench bleed the master cylinder, one of which is to mount it into a bench vise, fill the reservoirs, attach tubes that loop back up into the reservoirs and push the plunger slowly with a screwdriver. This works, but companies like Phoenix Systems has an even better idea and their one-man brake bleeder tool kit was just what we needed. We liked the idea of mounting the master cylinder to the car for stability, and using the brake pedal for leverage.

Phoenix Systems V-12 Brake Bleeder Kit
Part # 2003

  • Patented Reverse Fluid Injection
  • GSA, Military, OEM, and ABS approved
  • Single technician operation
  • Removes trapped air in brake systems which is the top cause of a “spongy pedal”
  • Portable, lightweight, durable
  • No electricity or pressurized air required
  • Cost-effective and multi-functional
  • Constructed from zytel nylon and simple to disassemble
  • Includes instructional DVD

Included in the Phoenix Systems V-12 Brake Bleeder kit is a set of fittings and clear vinyl tubes that you can use for bleeding your brakes, and for bleeding the master cylinder. We attached the proper fittings to the master cylinder, installed the tubes and looped them back into the reservoir, holding them in place with the clips provided in the kit. Then we simply filled the reservoirs and slowly pushed the brake pedal until there was no more air passing from the cylinder bores through the tubes and back into the reservoir.

Once that was completed, we attached the brake lines and used the brake bleeder tool to bleed our brakes. We filled the container with fresh brake fluid, replacing the cap and attaching the tube to the outlet side. We slowly pumped the handle a few times to prime the system, drawing fluid up into the tool itself. Then we attached the opposite end to the bleeder screw on the furthest wheel from the master cylinder first and opened the bleeder screw slightly. When you pump the tool, it draws fluid up from the container and pushes it out through the bleeder screw and up to the master cylinder.

This method is called reverse bleeding; it makes the job simple and it also helps to get all of the air out of the system by pushing it up through the brake lines. It makes sense: air is lighter and travels up, so why not push the air bubbles up instead of trying to push them down? The tool makes this task an easy, one-man job and it works great.

With the brakes bled, there were two things left to do before enjoying the new disc brakes. The final step is to take our car to the alignment shop, but before we drive it we need to adjust the rear brake bias. You can opt to use a factory proportioning valve, or an adjustable valve like we did on our Belvedere.

The meeting of beauty and function: ditching the old, unreliable drum brakes and adding the confidence-building reliability of disc brakes.

An adjustable valve mounts in the rear brake circuit and you have to make small adjustments to get the proper brake bias. Approximately 85% of the braking is done at the front, and the front calipers hold a lot more fluid than the rear wheel cylinders, so start with the valve adjusted approximately half-way and turn it counter-clockwise a turn at a time to decrease pressure going to the rear brakes.

To test your brakes, simply make a few short runs at medium speed and hit the brakes. If the rear tires lock up before the front, then pressure needs to be adjusted for less braking in the rear. Whatever adjustable proportioning valve you get, read the instructions that come with it. You can increase or decrease brake pressure with a simple turn of the knob, and you might have to try it a couple times before you get the right combination, but all it takes is a few quick stops and you’re on your way.

Final Notes and Suggestions

That’s our installation, and it took us about a day to complete. These aren’t the best brakes available for an upgrade, but they are better than drums all around, and this upgrade is very affordable for those on a budget who want to retain the factory look. Some things to consider while you’re doing this upgrade include replacing the rear brake hose (ours was shot) and replacing the rear wheel cylinders – being sure that they are similar in size to those from the “donor” car parts.

It may not be necessary, but if your brakes are dragging after the swap, a couple turns of this nut on the pushrod (arrow) will help.

One problem we encountered was that the brakes seemed to drag a little, so we found out that making an adjustment to the booster pushrod (arrow in picture) was all it took for us to get full use of our brakes again. The pushrod should not apply any pressure to the master cylinder until you push the pedal, so if there is pressure you can adjust the nut by turning it in about two or three turns. It should be approximately 3/16-inch from contact with the plunger on the master cylinder.

We removed the master cylinder, leaving the lines attached, then turned the nut in and bolted the master cylinder back up to the booster and we had full pedal and could start making our adjustments to the proportioning valve. To adjust, start at about midpoint, test your brakes, and adjust the knob for more pressure or less pressure to the rear brakes until you get all four wheels grabbing at the same time, and not locking up only one axle.

Just remember that when you’re working on your brakes, make sure everything is working properly before you head out on the road, because stopped traffic ahead of you is not the time to find out that you forgot to tighten something, or that your brakes aren’t seated properly. Seat the pads to the rotors by braking from 40 or 50 mph to about 10 mph several times, without coming to a complete stop.

Eventually, we would like to do a full four-wheel disc brake upgrade, but for now we’re satisfied with our front disc brake conversion. It’s off to the alignment shop next, and then we’re ready to cruise with a little more confidence in our Plymouth’s braking ability.

About the author

Michael Harding

Michael is a Power Automedia contributor and automotive enthusiast who doesn’t discriminate. Although Mopar is in his blood, he loves any car that looks great and drives even faster.
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