All of the advancements in automotive technology that are wrapped up in our modern daily drivers are easy to take for granted, but if you turn back the clock, all of these safety, convenience, and comfort updates were once an expensive option, or perhaps not even available in the time period of your project car. The basic disc brake system is an example of this type of feature. Developed around the turn of the century, disc brakes did not become a popular option until the early 1960s, and they were only seen on domestic and foreign sports vehicles at the time. Vehicles with rear drum brakes were still available in the early twenty-first century, but now days it’s a rare budget vehicle that doesn’t have four-wheel disc brakes.
Manufacturers began selling disc brakes as a one-two punch of improved braking performance and fewer moving parts for easier assembly. Drum brakes may be lighter in the long run, but they are significantly more difficult to install (both on the assembly line and in the field), and they are more prone to brake fade, contamination, and thermal degradation of the shoes, springs, and other elements. Disc brakes, on the other hand, have fewer moving components, run cooler, and are less prone to brake fade. As a result, as the 1970s progressed, automakers gradually chose disc brakes as the primary front brake system on automobiles. Today, due to businesses like Custom Car Help, you can convert just about anything on four wheels to use front disc brakes (at a minimum) or even 4-wheel disc brakes. Hundreds of disc brake conversion kits are available for everything from pre-war hot rods to muscle cars and historic trucks.
What’s the Difference Between Disc and Drum Brakes?
While we quickly mentioned some of the advantages of disc brakes in our opening paragraph, we wanted to take the time to fully explain how each braking system works. When you understand how drum and disc brakes work and how well they stop your automobile, you’ll be able to completely appreciate our headline, “Why didn’t I do this sooner?”
We’ll start with drum brakes, as many of you are considering using a conversion kit to replace them with modern disc brakes. The drum brake system is made up of a backing plate that holds the primary and secondary brake shoe linings in place, a hydraulic wheel cylinder, and mounting hardware/return springs that hold the brake shoes and wheel cylinder in place. A brake drum covers the system, which is connected to the wheels by axles, hubs, and wheel studs. When the brake pedal and master cylinder supply hydraulic pressure, the internal pistons of the wheel cylinder push outward on the brake shoes, which move outward and contact the drum, applying friction force to slow the drum, which in turn slows the attached wheels.
Drum brakes did the job back in the day, but they were notorious for storing heat, which caused brake fading, a more complex system with more moving parts, brake “grabbing” when wet, and the requirement for manual cleaning of the drum brake assembly on a regular basis. Consider today’s highway speeds, as well as the added performance we put to our old muscle cars, hot rods, and pickup trucks, and it’s clear that drum brakes are just hazardous by today’s standards. Check out this NHTSA report on the advantages of dual bowl master cylinders and converting drum brakes to disc brakes for yourself!
Disc brakes, on the other hand, have a simpler function and are much easier to maintain. They are less prone to “grabbing” in wet weather and also self-clean. Furthermore, because of their “open” shape, they are lighter, have better stopping power, and can disperse heat more easily. All of the check boxes in the right column demonstrate why almost everyone wants to upgrade their traditional drum brake ride to disc brakes. Disc brake conversion kits/upgrades, thankfully, are very much a bolt on and go affair these days, requiring only basic hand tools and an afternoon in the garage!
While a drum brake uses outward force on the brake shoes to slow the braking drum, a disc brake system uses a caliper assembly with one or more pistons that is placed over the disc brake rotor to work more efficiently in a “C-clamp” fashion (which is keyed to the wheels via the axle or hub, just like a drum brake). This clamping force is larger than that of a drum brake, and this is where the disc brake pads’ self-cleaning function kicks in, scraping away old lining material, dirt, and debris to keep the brake rotor clean. In comparison to the enclosed brake drum enclosing the drum brake components, the “open” design of the disc brake system allows for more heat dissipation.
What is the procedure for converting drum brakes to disc brakes?
We’ve gone through the distinctions between drum and disc brakes, as well as all the reasons why you should put discs on at least the front of your hot rod, muscle car, or classic truck, but the key question for most people is how to make the switch. While we don’t have space in our buyer’s guide to go over every make and model conversion available (that’s what the product instructions are for!), we can give you an outline of the conversion process, so you know what to expect. But don’t worry, all of the kits we sell come with everything you need to complete the job, including detailed instructions, so consider this merely a primer.
Removing the old drum brakes is the first step in converting to disc brakes.
Because so many early muscle cars and pre-war hot rods were designed with drum brakes as the primary front braking system, it’s a safe bet that if you pick up a project car, it’ll still be rolling on drums (and they’ll almost probably be seized up from sitting!). Obviously, the old drum brake components must be removed first. The drum with bearing hub, followed by the backing plate with brake shoes, wheel cylinder, and hardware, may normally be removed as a whole unit for the front brakes we’re focusing on. Remove the old hose at the frame rail connection and you should have a naked drum brake spindle to clean and prepare. Disc brake kits require their own flexible brake hose that differs from a drum brake hose, so remove the old hose at the frame rail connection.
An adapter and precise sized wheel bearings are included in most drum to disc brake conversion kits, allowing a popular disc brake rotor to be installed on the original drum spindle. A unique caliper adapter bracket is used to mount the disc brake caliper once the rotor has been installed. So, as long as the drum brake spindle is in good working order, you’re set to go with most drum to disc conversion kits. Replacement drum spindles that are modern forged spindles are available for various hot rod applications. The forging is stronger than the original cast spindle and any clearance or machining needed to install the disc brake system is already integrated into this new spindle, making it a simple switch. These spindles are ideal if you’re starting from scratch or if the existing spindles have been destroyed by a defective wheel bearing, an accident, or another issue.
When converting a muscle car or classic truck from drum to disc brakes, the drum brake spindle is frequently replaced with a disc brake spindle. If this is the case, our disc brake conversion kit will either include the needed spindles or provide information on how to obtain them for your conversion. We do, however, provide various drum to disc brake conversion kits for muscle vehicles that keep the drum brake spindle, making the transition simple if your spindles are in excellent shape. Many of our replacement spindles come with a 2- or 3-inch drop option, giving you the lowered stance, you want without sacrificing suspension ride quality or handling.
Although many will question its usefulness on lighter automobiles and pickup trucks, rear disc brake conversions are often installed similarly to popular front disc brake conversion kits. Although the front brake system handles up to 70% of your braking, a rear disc conversion not only eliminates the shortcomings of drum brakes in their entirety, but with a large-window wheel choice, rear disc brakes also complement the front disc brake package. We highly recommend adding a rear disc brake modification to your design for the minimal additional cost (usually a slip-on rotor with brake caliper and adapter bracket).
You’ll never have to deal with the intricacy of a drum brake system or the troubles that come with them again.