Tech Install: Master Power Brakes Disc Brake Swap For 15-Inch Wheels

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We’ve taken our 1965 Plymouth Belvedere II out to the track at Willow Springs, and also to Adams Motorsports Park, a local track in Riverside, California, where the recent SoCal Challenge was held a couple times this year. Before we hit the tracks, though, we had to perform a brake upgrade because we knew the four-wheel drum brakes weren’t going to cut it. We went with a common upgrade for these Mopars in the form of a factory style front disc brake set up.

racebel

Just a couple of laps with the old brakes, and brake fade killed our confidence. We decided to call on Master Power Brakes for a four-wheel disc brake upgrade.

While the factory style front disc brake upgrade is sufficient for cruising and for daily drivers, we found out quickly that the brakes couldn’t take the heat on race tracks. If we really want to be competitive, we need better brakes. The factory brakes were designed well and serve a purpose, but racing wasn’t part of the plan.

Like many holdouts in the musclecar world, we are fond of our 15-inch rally wheels, and began looking for a better braking system that would allow us to race the car, but also to keep our rally wheels. Not everyone has jumped on the bandwagon for big brakes kits because they require 17-inch or larger wheels, and that alone can exceed a budget in a hurry.

Rest assured, there’s great news on the horizon for those holdouts who want to keep their 15-inch wheels, and Master Power Brakes brings us that much needed upgrade in the form of their new Rallye Series front disc brake conversion kits.

All of the engineering and the design that goes into these kits are to give your car the performance of a big brake kit, but in a compact package. -Mark Chichester

Mark Chichester, Sales Representative at MP Brakes, said, “We felt it was time to freshen up our product line and the need for better performing brakes to fit inside a 15-inch wheel.” That freshening up filled the gap, and allowed us to make an upgrade, and still keep our rally wheels. For this Garage Series installment, we’re going to install confidence on our 1965 Plymouth Belvedere II.

We took a closer look at the new conversion kits from MP Brakes, and also looked at their Pro Driver Series disc brake kits for the rear. Even though they use the same caliper as the Rallye Series, these kits are designed to fit behind 16 inch and larger wheels, but will still fit behind some 15-inch wheels. We requested a template from MP Brakes, and found out that the Pro Driver Series rear disc brake kit would work with our 15-inch rally wheels – with a few modifications.

Converting to four-wheel disc brakes is as simple as ordering two kits: the Rallye Series for the front, and the Pro Driver Series for the rear.

Master Power Brakes

Front: Rallye Kit – Part #DB2311B
Rear: Pro Driver Kit – Part #DB4320BR

  • Four-piston billet aluminum calipers
  • Slotted/drilled rotors
  • Braided brake hoses
  • Parking brake incorporated into rear rotor
  • Includes hardware, brackets, spacers
  • DOT 3 and DOT 4 compatible
  • Hawk HB100 brake pads
  • Options include:
    • Master cylinder
    • Brake booster
    • Proportioning valve

Dual Purpose Classic Cars

Even though the autocross rage is to install 18-inch custom wheels with steamrollers all the way around and equally huge disc brake kits, we’re using our Plymouth for both racing and for cruising. While we do have plans for 18-inch wheels and fat tires, we still like to put our “cop car” rally wheels on the old girl and cruise. It has a bit of the sleeper look to it, and we like that about it.

There’s a big difference between the factory style front disc brake kits and these four-piston caliper kits from MP Brakes. While most factory style disc brakes are typically a single-piston, slider-type caliper, the Rallye Series and Pro Driver Series kits include billet aluminum, four-piston calipers, that are mounted in a fixed position.

The kits are designed to be bolted onto factory spindles and differentials for many classic American musclecars, whether you have drums or discs currently on the car. You can also order just about any part you need to complete the conversion to your own car, including a new master cylinder, brake booster, or proportioning valve, to name a few.

The billet aluminum calipers look great, and the brackets are simple, without any need to fabricate anything on the car.

This means that you’re not hunting down spindles and brackets at the wrecking yard, and you’re not paying someone hundreds of dollars to fabricate caliper brackets to adapt factory calipers to your spindle or axle housing. Everything that you need is included in the kits.

Chichester said, “All of the engineering and the design that goes into these kits are to give your car the performance of a big brake kit, but in a compact package.” These new brakes will give you the confidence you need to drive your car to more than just a weekly cruise night or car show.

Single Piston Vs. Multi-Piston Calipers

Many factory brake calipers slide on the caliper bracket or pins. While this is okay for a daily driver, it doesn’t offer the same performance as a multi-piston caliper. The calipers slide and need to remain lubed; if they aren’t maintained, it’s possible for the caliper to bind up and not perform properly.

A sliding caliper typically has a single piston, and when the brakes are applied the inside piston pushes the pad against the rotor, which in turn literally pulls the caliper away from the rotor until the outer brake pad makes contact with the rotor, and the pads squeeze the rotor. The outer brake pad needs to be pulled towards the rotor, so if the caliper isn’t sliding properly because of excessive heat, then braking performance is decreased, and the brake pads can wear unevenly.

Left: The sliding caliper pulls the outer brake pad into the rotor, if the caliper binds up, the pad doesn't move. Right: the four-piston, fixed caliper applies pressure to both pads and they squeeze the brake rotor simultaneously.

MP Brakes’ multi-piston calipers are fixed to the spindle so they don’t move. When the brakes are applied, equal pressure is applied from both sides of the rotor as the pistons press the pads against the brake rotor, and this provides an even clamping force on the rotor. This also applies the pressure on a larger surface area, which requires less pedal effort.

Replacing The Front Brakes

We removed the existing setup, straight down to the steering knuckle. Although we had previously upgraded our front brakes, it wasn’t a problem. One call to MP Brakes and we were given the correct part number of the kit we needed. If you still have drum brakes, they can also provide you with a different kit to upgrade your brakes.

The first part to install is the caliper bracket, and it bolts directly to the spindle with the two supplied, grade-8 bolts. Although the bracket may look like it can fit on the spindle a couple of different ways, we made sure to install it correctly so that the caliper can be bolted onto the proper side of the bracket. With the bracket in place, we then installed the brake rotor.

Be sure to mount the caliper bracket in the proper direction; the brake rotors come with the bearings and races installed, and greased.

The brake rotors that come with this kit are drilled and slotted. Called ‘power slots’, these slots help swipe built up gasses between the brake pad and the rotor. The drilling on the rotors helps to cool the rotor, and also makes the rotors a little bit lighter. Master Power installs the races, wheel bearings, and the seals on the rotors, and the bearings are pre-greased. You simply install the rotor onto the spindle, and they recommend that you do not add more grease to the bearings.

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Since not all factory parts are exactly the same, spacer washers are included to center the caliper on the rotor.

When installing the nut onto the spindle, the recommended way to tighten the nut is to get it snug and spin the rotor while loosening and re-tightening the nut. This repeated process will help to seat the bearings to the spindle; the rotor should spin, but if it spins more than one full rotation then the nut might not be snug enough. Once this process is repeated, a final turn of the nut will snug it up and then the crown nut and cotter pin can be installed.

We next installed the caliper, which needs to be centered to the rotor. With everything tightened up, we measured the gaps on each side of the rotor and used the included spacers to locate the caliper in the proper position.

The brake hose can be a little tricky, so it’s best to install the hose loosely at first, then crank the steering from left to right to make sure that there isn’t any binding on the brake hose. We also installed the front wheel to make sure that the hose didn’t rub against the tire. Once we were satisfied with the brake hose, we tightened everything down, double-checking all bolts a second time before moving on to the rear.

When installing the brake hose, install it loosely and turn the wheels lock to lock to make sure that the hose doesn't bind up or rub against anything.

Replacing The Rear Brakes

The rear brakes might require some advance test fitting, depending on your application. MP Brakes will provide you with a PDF template that you can print and cut out so that you can see if there will be wheel clearance issues. Because the parking brake is incorporated into the rotor, it’s a little larger than the front rotor, and might not fit inside some 15-inch wheels, so do your homework on this first. We determined that the Pro Driver Series would fit in our 15-inch wheels using a 1/2-inch wheel spacer, which required installing longer wheel studs.

This template that we got from MP Brakes helped us come to the initial conclusion that a 1/2-inch wheel spacer was needed. Once we received the kit, we placed it inside the wheel to verify our findings, and it would fit with the spacer.

For the rear disc brake conversion, we needed to remove the entire rear drum brake assembly. We also had to pull the axles out so that the backing plate can be removed. Removing the axles gives you an opportunity to replace wheel bearings if necessary, we replaced ours when we did a rearend upgrade a few months ago, but still inspected them when we removed the axles. An axle puller is a good tool to have handy in case the axles don’t pull out of the housing easily.

We removed the five bolts on the bearing retainer, and then pulled the axle out, leaving the backing plate sitting on the differential housing. To remove the backing plate, we disconnected the brake line, and the parking brake cable was disassembled. A Lokar parking brake cable will replace the factory parking brake cables.

To install the rear brake bracket, it needs to be mounted on the axle housing prior to reinstalling the axle. There is an adapter plate that will bolt to the housing end, and it’s attached loosely to the bracket. If your axle flanges have a hole for access to the bearing retainer nuts, then the adapter can be tightened to the bracket. If you don’t have access to the retainer nuts, then the assembly will have to be kept loose until the axles are installed and the retainers are tightened down. Our Moser axles allowed us access, making the installation much easier.

Since the new rotor has an integrated parking brake, the old cables had to go, as well as the backing plate and hardware.

Even though our axle bearing is sealed, we still applied silicone RTV sealer to both sides of the adapter in place of a gasket. We slid the assembly over the five bolts in the housing end, then slid the axle back into place and tightened down the retainer nuts. We installed the brake rotor, and then the caliper was test fit onto the bracket like we did with the front.

mp120

Spacers are included to center the rear caliper to the rotor. Like the front, the caliper needs to be centered on the rotor to function properly.

With the rear caliper, the included spacers need to be mounted between the caliper bracket and the rear brake bracket, so we tightened everything up, measured the distance between caliper and rotor on both sides of the rotor, and we used the proper spacers to center the caliper to the rotor. Keep in mind that the wheel holds the rotor in place, so we put a couple of lug nuts on the studs to cinch the rotor down to the axle, then we could properly center the caliper to the rotor.

The brake hose attaches to the factory brake line that was attached to the rear wheel cylinder. We gently bent it away from it’s prior position, and with the banjo end of the brake hose loosely attached to the caliper we determined where it was best to attach the brake line. The included clamp and bracket were attached to the axle tube, and tightened up, and then the brake line was bent into place to connect to the brake hose. We made sure that there wasn’t any interference with moving parts, and tightened everything up, again double-checking all bolts to make sure they were tight.

The rear brake hose attaches to the solid brake line using included clips and a clamp to hold the clips in place. It's a very clean and easy set up.

The spacer was installed over the studs, and the wheel was installed and tightened down and we slowly rotated the rear wheel to make sure that nothing scraped or came in contact with the calipers. It’s a close fit, but we knew that going into this upgrade. With the proper planning and some ingenuity, we got what we were aiming for: four-wheel disc brakes.

Final Steps To Being Roadworthy

It would be difficult to have a kit for every application, so we are aware that there might be the need for some custom fabrication, as with any custom install.

Although the Pro Driver Series was not specifically designed for 15-inch wheels, we were able to make a few modifications to get them to work for us. Chichester told us, “It would be difficult to have a kit for every application, so we are aware that there might be the need for some custom fabrication, as with any custom install.” This is why proper planning is important, and installing a four-piston caliper in the rear is no exception to that rule.

After we bench bled the master cylinder with MP Brakes’ bleeder kit, we began to bleed the brakes. Starting with the furthest caliper from the master cylinder, we bled the brakes using the tried-and-true method of enlisting the help of a friend. There are two bleeder screws on each caliper because the calipers can be mounted on the right or left side. The upper screw is where you want to bleed the brakes from, because air travels up and it’s easier to bleed the air out from the top.

mp39

Dual bleeder screws allows this caliper to mounted right or left, leading or trailing.

Master Power provides hoses to attach to the caliper, and recommends that you pump the brakes a couple times to fill the calipers with fluid before bleeding them. We bled the air out of each caliper three times, making sure there were no more bubbles in the hose. The left front was bled last, and then the wheels were installed, the car was put back on the ground, and we began the process of bedding the pads and rotors.

Master Power also recommends that normal driving is done for the first few days to give time for the zinc coating to wear off and for proper bedding of the pads and rotors. If spirited driving is done prior to this, the rotors and pads could overheat, resulting in warped or glazed rotors, which could diminish braking performance. The bedding instructions are included, and following those instructions is paramount in order to get the best performance from your MP Brakes conversion.

Driving Impressions And Performance

We could already tell that our brakes were performing far better than before, but it was important to follow procedures so we drove the car for a few days before any spirited driving. After bedding the pads and rotors, we took our Plymouth back to Adams Motorsports Park to run the car around the track a few times, and see how much our braking performance has improved.

valve

A proportioning valve, also available from Master Power, is required to set brake bias. We chose an adjustable valve.

It’s required to install an adjustable proportioning valve on the rear brake line to limit the rear brake pressure, as you want most of the braking to be done by the front brakes. A couple of times around the track, and a couple of turns of the knob, helped us to dial in the proper front/rear bias on our new Master Power disc brake kits.

The one thing that we didn’t like was that our rally wheels hide the calipers and rotors from view, and they are way too nice to hide. Showing them off will have to wait for our 18-inch Weld Racing wheels and Mickey Thompson tires to be installed, but in the meantime we wanted to heat up the brakes, and find out if our prior experiences with brake fade were going to stay in the past.

We pushed it hard, putting a lot of demand on the brake pedal and our braking confidence was increased significantly. After several quick, aggressive stops, overall braking performance was enhanced, and the pedal remained firm, without requiring a lot of force.

belvedereartsy

With our MP Brakes conversion, we’re ready for the big track at Willow Springs Raceway. Photo: Kevin Yuen.

After a few more aggressive laps at the track, we didn’t experience any issues with brake fade or overheating, like we had before. Prior to the upgrade, hitting the brakes before a hairpin turn felt like driving on ice because the brakes didn’t grab after they had heated up. That all changed after the conversion.

The brakes performed as we expected, and it gave us just enough confidence to brake a little later in the turns, and to keep our speed up a little during the approach. No more funky smells emanating from behind the wheels after back-to-back hard braking runs.

We spent about a day installing our new MP Brakes disc brake conversion kits without any special tools – or a lift. It was all done in the garage, and other than bleeding the brakes it was a one-man job. If you’ve been looking to install some confidence on your classic car, be sure to check out the MP Brakes web site, they are constantly updating their products to provide you with the stopping power and confidence that you’ve been looking for.

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.
Read My Articles

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