Drum to Disc Brake ConversionLast Updated October 9, 2023 | Alison Smith
If you’re working on restoring a classic car or truck, chances are the vehicle has drum brakes. Front disc brakes didn’t start becoming standard until the late 1970s. Before that, most vehicles had drum brakes in both the front and rear. Rear disc brakes became more common a few decades later.
As the front brakes provide most of the stopping power, many modern cars still use rear drum brakes due to their affordability. Disc brake conversions are popular restomods for classic vehicles with drum brakes, although it’s more common to just do the front brakes.
Why Convert from Drum Brakes to Disc Brakes?
On a basic level, drum brakes consist of a round drum, a piston, and two brake shoes. Pressing the brake pedal causes the piston to push the brake shoes against the drum to bring your vehicle to a stop.
Disc brakes use a brake disc, a piston, caliper, and brake pads. Applying the brake pedal forces the pads into the rotor so you can come to a stop. Disc brakes have two main benefits that make them safer and more reliable than drum brakes.
Less Heat Buildup
Although drum brakes are cheaper, they don’t disperse heat as well as disc brakes. If you’re driving down a hill or somewhere you need to repeatedly use your brakes, heat can build up inside the brake drum. Too much heat causes the drum brakes to fade, reducing their stopping power. Since disc brakes are exposed to the outside air, they’re able to stay much cooler during heavy braking.
Superior Performance in Wet Conditions
Due to their design, drum brakes also have a tendency to collect water in rainy weather. This makes them less effective in wet conditions. Because water can pool inside the drum brake, it can also cause rust and corrosion. Disc brakes are much more effective in wet conditions as they don’t collect water.
How Much Is a Disc Brake Conversion?
Disc brake conversion kits run anywhere from a few hundred dollars to several thousand dollars. The cost to convert drum brakes to disc brakes mainly depends on how comprehensive the kit is and how many parts are included. If you aren’t experienced with brakes, then you may need to pay additional labor costs as well.
How to Convert Drum Brakes to Disc Brakes
The exact process of converting drum brakes to disc brakes will vary from vehicle to vehicle, but for the most part it’s the same. For this specific guide, we installed a front disc brake conversion kit on a 1965 Mustang. The Scott Drake disc brake conversion kit we used contains all the parts needed to get the job done: brake calipers, 4-lug 10.5" rotors, brake pads and rubber hoses, and all the installation hardware. Check your kit to ensure you have all the parts you need to complete the installation.
Please Note: Please keep in mind that this guide is a tool to help you install the parts on your vehicle. If you don’t feel confident in performing this installation properly on your own, have a professional install the parts for you.
The tools required will vary depending on the manufacturer and model of your vehicle, but you can expect something along these lines.
- Lift or Jack and Jack Stands
- 1/2’’ Ratchet
- 15/16’’ Socket
- 3/8’’ Ratchet
- 9/16’’ Socket
- 3/8’’ Allen Key
- 5/8’’ Wrench
- 9/16’’ Wrench
- 3/8’’ Line Wrench
- Flathead Screwdriver
- Channel Lock
- Rotary Tool
- Rubber Mallet
- Safety Glasses
Step 1: Raise Vehicle & Remove Wheels
Raise the car off the ground using a lift or jack and jack stands and remove the two front wheels.
Step 2: Remove Dust Cup from Drum
Before you can start disassembling the drum brakes, you must remove the dust cup.
Step 3: Remove Cotter Pin
Now that the dust cap is removed, squeeze the cotter pin and remove it so you can unscrew the retaining nut.
Step 4: Remove Retaining Nut
Next, you’ll remove the retaining nut using channel lock pliers.
Step 5: Remove Washer & Bearing
To remove the washer and bearing, give the drum a good tap. They should pop right on out.
Step 6: Remove Brake Drum
With everything out of the way, you can now remove the brake drum.
Step 7: Disconnect Brake Line
At this point, you’re going to disconnect the brake line. The brake line in this 1965 Mustang is most likely original, so we’ll replace it with a new brake line. If you still have factory brake lines, you may want to consider upgrading as well.
Pro Tip: You may end up damaging the brake line in the process of removal. In our case, the brake line was beyond repair, so we ended up cutting it.
Step 8: Remove Retaining Clip
With the brake line disconnected, you can remove the retaining clip. You may have to remove some of the undercoating to remove the clip.
Step 9: Remove Bolts from Backing Plate
With the line disconnected, the next step is to remove the backing plate. It’s held on by four bolts that you’ll need to remove.
Step 10: Remove Backing Plate & Drum
Once you get the bolts off, you can remove the backing plate with the drum. You can use a mallet to gently tap on the back if needed.
Step 11: Remove Gasket Remnants & Clean the Surface
Once the backing plate and drum are off, you can remove any gasket remnants and clean the surface using a rotary tool and rag.
Step 12: Install Caliper Mounting Bracket
When you get everything nice and clean, you can install the caliper mounting bracket. Line the bolts up with the factory holes and tighten them down.
Step 13: Start Assembling Rotor
Remove the metal ring from the seal and place it on the spindle with the tapered side facing inward.
Step 14: Properly Grease Bearings
Get a good amount of grease in your hand and work it through the bearing. If you have a bearing packer, you can use it here. If not, this is the old school way of doing it. Make sure you work the grease in and out of the bearing.
Step 15: Set Bearing in Back of Rotor
After the bearing is all greased up, put it in the back of the rotor.
Step 16: Place Seal on Top of Bearing
Now that the bearing is in the rotor, place the seal on top of the bearing.
Step 17: Grease the Spindle
Apply a generous amount of grease to the spindle.
Step 18: Place Rotor on Spindle
After greasing the spindle, it’s time to put the rotor on.
Step 19: Grease the Smaller Bearing
Now you’re going to grease the smaller bearing, working it through the same way you did with the larger bearing. Make sure it covers all the rollers by spinning them around in your hand.
Step 20: Place Smaller Bearing on Spindle
After the smaller bearing is greased, place it on the spindle.
Step 21: Install Washer & Retaining Nut
Slide the washer on top of the smaller bearing and place the retaining nut on top. Tighten the nut down.
Step 22: Install Cotter Pin
When everything is tightened down, install the cotter pin.
Step 23: Install Grease Cap
After the cotter pin is installed, put the grease cap on. You may need a rubber mallet to hammer it down.
Step 24: Grease Caliper Brackets
Before installing the calipers, grease the caliper brackets.
Step 25: Mount Caliper
Place the caliper on the greased bracket and tighten.
Step 26: Install Banjo Bolt with Brake Line
After the caliper is mounted, you’re going to install the brake line using a banjo bolt. Put one washer on each side of the line and tighten.
Step 27: Connect Brake Line
With everything else done, you can reconnect the brake line. Put the hose through and connect the line. Slide the retainer in, then tighten the brake line.
Step 28: Repeat Process on Other Side
Once you’re done with one side, you can complete the same process on the other side.
Step 29: Bleed Brakes
After installing the front disc brakes on each side, the last step is to bleed your brakes.
Step 30: Reinstall Wheels & Tires
With your tires and wheels back on the car, it’s time to enjoy your modern disc brake setup.
Are Disc Brakes Worth the Investment?
Because of their superior performance, disc brakes are worth the investment and time it takes to install them. Compared to drum brakes, disc brakes offer significantly more stopping power, reliability, and performance.
Disc brakes are especially important if you plan on doing any type of racing. You’re going to need a reliable braking system that can stop quickly and not fade with repeated use. If you’re on a limited budget, replacing the front disc brakes will have the most impact.
Sources: Brakes: Drum vs Disc, Edmunds | How Drum Brakes Work, How Stuff Works | How Disc Brakes Work, How Stuff Works | How Do Drum Brakes Actually Work? , Car Throttle | Pros and Cons of Drum Brakes, Haynes