How Brake Shoes Work
Brake Shoes No matter how complex and computer operated today’s vehicles become, there are very few things more important than the brakes. Most vehicles on the road today are equipped with what is called a disc-drum set up. This refers to the style of brakes front and rear of the vehicle, disc being fronts and drum the rears. Some vehicles have a disc-disc set up (disc front and rear), which is the newest and most efficient of the combination used. Older vehicles used a drum-drum set up; this combination doesn’t provide good stopping power and hasn’t been used for years. Drum brakes were the standard for many years in the automotive industry but they were phased out as the front brakes in favor of disc brakes in the late 60’s and early 70’s depending on the manufacturer. In this article we will talk about the brake shoes, which are the friction material for the drum brakes. Brake shoes come in sets of four, two for each side. There are two different brake shoes per side, a primary shoe that has a little less friction material on it and goes toward the front of the vehicle and the secondary shoe that has more material and faces the rear of the vehicle. Some vehicles use shoes with the same amount of friction material, on those it doesn’t matter which shoe is facing front or rear. When you push the brake, hydraulic pressure forces the shoes out making contact with the inside of the brake drum, this is the friction that stops your vehicle. The emergency brake on a disc-drum combination is also the job of the brake shoes, while mechanical in nature, the emergency brake uses the same principle of forcing the shoes out against the drum, helping to hold the vehicle in place. Vehicles with rear disc brakes will still use a smaller drum brake in the center of the rotor for the emergency brake; they have proven to be the most trouble free and reliable type of emergency brake. Brake shoes come in a wide variety of price ranges, from the least expensive (re-manufactured aftermarket) to the most expensive (new OEM). When replacing your brake shoes, cost is always at the back of our minds, but this is really no place to skimp on quality, these are what stop your vehicle. New OEM (Original Equipment Manufacturer) shoes are made of higher quality material and will perform better over the long run than will an aftermarket shoe. Another difference in the shoes will be how the friction material is attached to the brake shoes; it is either bonded (glued) or riveted. Less expensive shoes tend to be bonded to the shoe; this process is less expensive than drilling and riveting, although some shoes are bonded from the factory due to the thickness of the friction material. Brake shoes tend to last about twice as long as the front pads on a vehicle due to the brake bias (front to rear ratio) and how well they are kept in adjustment.
When brake shoes begin to wear down, you will notice more travel in the emergency brake lever (pedal) and possibly a soft brake pedal. The latter of these is due to the fact that the brake system must displace more fluid to compensate for the missing friction material before the shoe contacts the drum. Drum brakes incorporate an automatic adjusting mechanism, unfortunately not may of them work as designed or they become frozen up do to the extreme heat they endure from the brakes. Some vehicles have a window or slot in the backing plate where you can access the adjuster to manually adjust the brakes, if not the wheel and drum must be removed from the vehicle to access the adjusting mechanism. When manually adjusting brakes, lift and support the vehicle, spin the wheel while using an adjusting spoon or small screwdriver to turn the adjuster wheel, adjust the shoes just until you can hear them rubbing the inside of the drum, but not so tight as to inhibit the wheel from rolling. If your rear drum brakes begin to grab or “lock-up” it could be due to over-adjustment or worn shoes contacting too much surface inside the drum. The shoe shouldn’t contact its entire surface area or they will grab. If you decide to replace the drum brakes on your vehicle, there are a few specialty tools that will make the job much easier. Anchor pin tools and spring tools will keep you from possibly hurting yourself trying to pry them off and on. As with any vehicle repair, wear the proper safety attire, and avoid breathing the dust created by the brakes wearing. Another thing to consider is replacement of all of the hardware in the drum brake assembly (combo kit). Springs can become brittle and lose their strength when they get hot and then cool, such as with the brakes. If when replacing your brake shoes, you notice any moisture around the wheel cylinder, it should be replaced. If the wheel cylinder fails, you will lose part of the braking system pressure and it may cause an accident. It is also advisable to replace the wheel cylinders as a set (both sides) if one is worn the other can’t be far behind. Early brake shoes were made of an asbestos based material, so breathing the dust created by them can be hazardous to your health. These materials were phased out many years ago in favor of safer materials that aren’t as dangerous. Regardless, breathing brake dust can cause long-term health issues; therefore it is recommended using a mask when replacing the brake shoes on your vehicle to filter out the fine particulates. If further technical assistance is needed, our certified car repair technicians are ready to answer your car questions. Related Car Repair Information