Let’s be honest for a second. Nobody gets into this hobby because they want to upgrade their stopping power. It’s the least glamorous mod on the list. But whether you’re prepping a WRX for the skidpad or you just want your ’68 F-150 to actually stop when you hit the pedal, a disc brake conversion is the smartest first move you can make.
Drum brakes are relics. They hate heat. They hate moisture. They hate dirt. And they need constant adjustment to work right. Discs? They’re cleaner. More consistent. Safer.
Зміст
The History of Stopping Power
Disc brakes didn’t become standard until the 1970s. Chrysler tried pushing them in the 1950s, but the market wasn’t ready. The real turning point was the mid-1960s. That’s when power brake systems became viable. Suddenly, the heavy pedal effort required for discs wasn’t a dealbreaker.
Even today, most modern vehicles keep rear drums. Why? Cost. Front brakes handle about 70 percent of the deceleration load. Manufacturers sacrifice rear performance to save a few bucks. You aren’t stuck with that compromise if you own an older rig.
Tools of the Trade
If you’re doing this yourself, you probably have the basics. But removing the old hardware is where you’ll bleed your budget and your sanity.
Assume your bolts are rusted shut. Assume the lubrication has turned to dust. A socket set and torque wrench won’t save you here. You need penetrating oil. A sledgehammer. Maybe a hacksaw. An acetylene torch is overkill but effective.
“Taking off your old brakes will probably pose the biggest challenge.”
You might need to pull springs, shocks, or an axle depending on the year and make of your vehicle. Don’t start cutting until you know the full scope of the disassembly.
Front Disc Brake Conversion
Working on a pre-1970 vehicle usually means more than a bolt-on swap. You’re often dealing with worn spindles and rusted hubs.
Stripping the Old Kit
- Remove the wheels and tires.
- Pry off the dust cap.
- Extract the center nut, washer, and brake-drum bolts.
- Disconnect the brake hose.
- Pull the drum.
Inspect the spindle. If it’s scored or corroded, replace it. If it’s clean, a good cleaning and reuse is fine. Secure the steering arm and you’re halfway there.
Assembling the New Setup
Conversion kits often come pre-assembled. If you’re pulling parts from a junkyard donor car, you’re on your own.
- Attach the rotor to the spindle.
- Install the bearing and nut, washer, and cotter pin.
- Snap the dust cap on.
- Mount the caliper assembly over the rotor.
- Attach new brake lines and pads.
- Reinstall the caliper.
- Put the wheels back on.
Once the hardware is together, you can’t just drive away. You need to bleed the brakes. Disconnecting lines introduces air into the system. Air compresses. Fluid doesn’t. Without bleeding, your pedal will feel spongy. It might even dip to the floor.
Master Cylinder Considerations
Changing to discs alters the hydraulic volume and pressure requirements. On pre-1970 vehicles, the stock master cylinder might not push enough fluid or handle the pressure changes correctly.
Check if you need a replacement. If so, you’ll need the master cylinder, booster, vacuum hose, and a proportioning valve. These are often sold as a kit. You can install this before or after the brake conversion. Just make sure you do it.
The rear conversion is a different beast entirely. You’ll need to handle the axle and the unique mounting points that rear discs require.
Rear Disc Brake Conversion and Parking Brake Mechanics
Car manufacturers stick to front discs and rear drums for one obvious reason: cost. It’s cheaper. But there’s a mechanical reason too. Drum brakes have a simple, cheap way to engage the parking brake. The cable pulls a lever connected directly to the brake shoes. Disc brakes are different.
The parking brake mechanism lives inside the caliper. A lever pushes against the piston. Sometimes it’s a separate drum tucked inside the rear rotor. It depends on whether you’re running single-piston or four-piston calipers.
This matters for your conversion. You might need a whole new parking brake system. If you’re lucky, your new brakes play nice with your existing setup. Then you just disconnect the cable before pulling the old drums and reconnect it after the new calipers are bolted on.
Removing The Drum Brakes
Rear drum removal is mostly the same as the front. Except for that annoying parking brake assembly.
Start with the wheels off. Then remove the dust cap, center nut, and washer. Undo the brake-drum bolts. Before the drum comes off, you have to disconnect the brake hose and the parking brake cable.
Once the drum is off, inspect the spindle. Replace it if it’s worn. Reuse it if it’s good. Reposition the steering arm and secure it.
Installing The Disc Brakes
Slide the rotor onto the spindle. Add the washer, bearing, and nut. Secure it with the cotter pin. Put the dust cap back on.
Now for the caliper.
Attach the new brake lines. Install the pads. Position the caliper over the rotor. Connect the parking brake linkage and the brake lines.
Put the wheels and tires back on. You’re almost done.
But wait.
Bleeding the brakes is non-negotiable. Refresh the fluid. Test the parking brake. Adjust it.
Parking Brake Adjustment
How tight should it be? Pull the hand lever. You should hear four clicks.
If the cable is loose, the car rolls. If it’s too tight, the brake drags. Dragging wears out pads rapidly. It also heats up the system. Find the sweet spot.
Disc Brake Conversion Kits
The conversion kit market is geared toward high-performance. Which means high cost.
Deciding between a kit and junkyard parts depends on your goal.
If you’re just upgrading brakes on an old beater, a kit might be overkill. It could cost more than donor parts.
Kits save time. Hunting through junkyard wrecks and auto store bins takes hours. A kit for a 1970 Ford Mustang runs $1,000 to $2,000. Doing it with junkyard parts costs one DIYer $800.
Kits range from $500 to $3,000. Lower-end kits use simple flat rotors. High-end kits have slotted rotors for cooling. They also focus on looks. Bright red racing calipers. Special finishes.
There’s no specific kit for every car. But there’s always a compatible one. Enthusiast forums and message boards are invaluable. Find out what fits your needs.
Conversion Kit Sources
Major manufacturers include Wilwood, Baer, and Summit Racing. Many online retailers sell these. And many other brands.
Lots More Information
Related HowStuffWorks Articles:
– How Air Brakes Work
– How Brakes Work
– How Anti-Lock Brakes Work
– How Disc Brakes Work
– How Drum Brakes Work
– When I put my car in park what really keeps it from moving?
Sources:
– Carley, Larry “Parking Brake Adjustment.” AA1car.com. 2005
– Cook, Miles. “How To Install A Power Brake Booster.” MustangMonthly.com
– Day, Richard. “How to Service and Repair Your Own Car.” Popular Science Publishing Company, Inc. 1973
– Ireland, Richard. Disc Brake Swap. Woodyg.com. 2001
– Larson, Rick. “Front Drum to Disc Brake Conversion for Classic Mustangs.” Vintage-mustang.com. 1996
– NationMaster.com. Encyclopedia Frederick William Lanchester
– Nextag.com. “Rear Disc Brake Conversion Kit.
– Off-road.com. “Rear Disc Brake Conversion.” 10/01/05
– Payne, Kenneth. “Front Drum To Disc Brake Conversion Guide For 1965-1972 Ford Trucks.” Ford-trucks.com. 1997
– Professional Mechanics Online. 2carpros.com
– Wendler, Andrew. Personal conversation. 10/29/08
– Werner, Rolf and Weed, Jim.
