You entrust your safety and the safety of your family to your car’s brakes. The brakes are a vital part of your car’s safety systems, and obviously stop your car when it needs to be stopped. You need to know that you can trust your brakes to work when you need them. While the casual driver may not realize it, there are actually a few different options when it comes to brakes: drums and discs. It can be beneficial to know about both.

Drum Brakes

Drum brakes are the earliest form of automobile brakes still in use. All forms of automobile brakes use friction to slow the wheels and the vehicle. Drum braking systems use shoes or pads that press against lining on the inside of the wheel to arrest the movement of the wheel. This form of braking has a natural self-applying quality, in which the shoes bite into the wheel without any additional application of force from the driver.

Drums are less expensive than discs, and are often used on economy vehicles. Lighter vehicles also make use of drums. However, there are a number of disadvantages to disc brakes, including:

Drum brakes are apt to overheat, which can cause the shoes to distort and cause vibration to the entire braking system.
Overheating can also cause brake fade. The heat from the braking can cause the shoes to lose their gripping abilities, meaning that the brakes may not be able to grip and braking may not occur.

Disc Brakes

Disc brakes present a significant advancement over drum brakes. Whereas drums press against the inner lining of the wheel to arrest the wheel’s movement, a disc brake’s pads are attached to a device called a brake caliper, which mechanically depresses on the wheels, stopping movement. Unlike drums, they are much better at dispersing heat, meaning that they are not as subject to the problem of brake fade. While brake fade may occur, it is far less likely in discs.

Discs are now more common than drums, as they provide superior braking power on larger vehicles. Smaller economy vehicles still commonly use drum brakes, as the weights involved make discs unnecessary. More and more hybrid cars are making use of the less-expensive drum brakes, as they make use of the energy generated from braking to charge the battery.

If you’ve been involved in a car accident caused by non-functioning brakes, you may be entitled to financial compensation. To learn more, visit the Wisconsin car accident attorneys of Habush Habush & Rottier today.

Joseph Devine

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DRUM BRAKE EVOLUTION

To understand the how we must first discuss the why. Brake technology has made quite a few advances in the last 100 years, but even back in the 1940s, Ford adapted changes to the way brakes were designed, much to the resistance of Henry Ford.

Henry Ford was fond of his mechanical brakes, and his marketing touted “Solid steel from pedal to wheel”. These mechanical rod operated brakes persisted until 1939, well behind Ford’s competitors. The problem with the brakes is that they required frequent adjustment, and were just plain dangerous at speed. They featured 12 inch diameter drums that could easily put a car into a spin if one brake rod was tighter than another. High speed stops proved to be hair raising experiences, and many felt that the new hydraulic or “juice” brakes introduced in 1939 to the Ford product line was a step up in safety and performance.

JUICE BRAKES

The first and by far the most important design improvement was the change from rods to hydraulic fluid to actuate the brake shoes. Although the design was originally invented in 1924, Ford resisted utilizing the design until 1939, with the backing plates, shoes, and drum assembly that in many ways the is same design used on cars today. There were a few key design issues that took some years of production to be recognized and improved upon. Along with other idiosyncrasies, Ford’s new adopted hydraulic design was a work in progress. The brakes required more pedal effort to stop the car than our modern drum brakes, a break in period, and even in some cases machine grinding to fit correctly.

Back in the 1940′s and 1950′s our hot rodding fore-fathers had limited resources and little access to sophisticated machinery, so often a “bolt on solution” was the most popular. From the way Ford designed their cars, these brake alternatives were just that.

The second major design improvement was the way the shoes were mounted on the backing plate. The 1940 brake shoes pivoted on a pin at the bottom and where actuated by a slave cylinder at the top. This design is known as “single leading shoe” or “leading and trailing shoe brakes”. When brake force is applied, both shoes pivot at the bottom attachment bolt and press against the drum with equal pressure. Shoe contact tended to stay in one spot and the wear was uneven. Pedal effort was high because none of the rotational force was used to help make the shoes press harder to the drum surface.

Living with the 1939 Ford brakes

To improve shoe to drum contact, the 1940 design utilized a pair of cams on the shoe pivots that moved each shoe in or out to eliminate high spots. Either lock nuts on the backing plate side of the brakes, or spring tension bolts allowed for adjustments to be made.

These spring tensioned bolt adjusters tend to resist staying in place, and the situation is even more aggravated if you chemically clean the backing plates for painting. Rust tended to create a resistance to turning of these spring bolts. The lower cam bolts on the design on the right tended to loosen as well, so when using the early Ford brakes periodic inspection is a must for optimal performance. Overall the design works well but requires maintenance.

A word about brake shoe grinding:

Brake grinding was common back in the day, as everyone was well aware that a little asbestos dust never hurt anybody! Perhaps no one thought of the disadvantage of grinding off of valuable braking material was a problem either. If the brakes where not ground down, they would eventually wear to the shape of the drums, but prior to that happening, the 1939 brakes had a nasty habit of grabbing and high spotting. This caused wheel lock at inopportune times, along with unpredictable braking. These features and disadvantages make the selection of the F100 truck brakes an easy choice.

Ford F100 pickup truck brake design

The F100 brakes are what is called a “Duo-Servo” design. This design works outperforms the 1939 leading edge design because it uses the rotation of the drums to cause the brake shoes to “twist” and press against the drum lining much harder. So much better in fact that they require less pedal effort and are less sensitive to high spotting. This also has the benefit of a more even brake shoe wear and longer shoe life. Let’s look closer at why the “Duo-Servo” design works so much better than the 1939 design.

At first glance the F100 design looks much like the 1940 design, but on closer examination we see that the shoes are not mounted on a stationary pivot point, but rather “floating” on a pin and spring assembly. The floating feature allows the brake shoes to twist and wedge themselves against the drum increasing braking friction. Through this servo action the shoes transmit motion to each other, rather than just one lead shoe doing all the work.

Throughout the 1950′s there was a revolution of sorts on brake development. Some of the larger more prestigious cars came equipped with this updated design. The major distinction was that the shoes now “floated” on the backing plates and took advantage of the rotation of the drum to grip harder. Ford recognized the advantage this would have on the heavier truck they produced during the early 1950′s. The point not lost on performance enthusiasts. Even though the early brake drums were 12 inches in diameter, the 11 inch F100 and F1 design was far superior in performance.

Curt Baker is a Charlotte NC based consultant specializing in foreclosure mediation in the commercial market. Curt works with Asset Solutions Group Inc and is focused on the Hospitality Industry in mediating debt, and restructuring financing for distressed properties. The company website is:

http://www.assetsolutionsgroup.net

Curt is also an accomplished author and builder of traditional hot rod automobiles. His passion has been on Ford cars of the early 1930′s and 1940′s, with emphasis on period correct restorations. His writings include The Traditional Ford Brake Book which isa detailed how to book on early Ford brake conversions.

http://so-car.blogspot.com/

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