Brake Drums

What are brake drums and where are they located?

Your vehicle’s brake drums are major components in a drum brake system. A drum brake system contains brake drums, shoes, backing plates, and wheel cylinders. Brake drums made from cast iron, bolt onto the wheel hubs or axles, and spin at the same rate as the wheels. The rest of the components are confined to the inside of the drum.  Inside each brake drum sits 1 wheel cylinder and 2 brake shoes bolted to the backing plate.  When you press the brake pedal, hydraulic pressure is transmitted to wheel cylinder, causing the pistons to expand, pushing the brake shoes against the inside surface of the drum.  The friction created  allows the vehicle to slow to a stop.  In a nutshell, your vehicle’s brakes convert kinetic energy to thermal energy.

Vehicles today have 4 brake discs.  Before, drum brakes were the standard, rear drum brakes were used and are still found on many vehicles today - for cost effective reasons.  If a car or truck is only equipped with brake drums, it will have 1 drum for each wheel in the vehicle's front and 1 for each wheel in the vehicle's rear.  If a car or truck only has brake drums in the rear, the vehicle will have 2 front brake rotors and 2 rear brake drums.

One advantage of a drum brake system is that the brake shoes will last longer than pads in a disc brake system, since there is a larger friction material contact area.  However, because of the design of drum brakes, they do not dissipate heat as well as a disc brake system.  As heat builds within the brake drum, the brakes become less effective.

How do I know if my brake drums need to be replaced?

Brake drums can be resurfaced, or machined as long as there is enough material to do so.  All brake drums have a discard diameter determined by the manufacturer, which is the maximum inside diameter the drum can be machined to before deemed unsafe and must be replaced (this information is often stamped into the outside of the drum itself).  Using a micrometer, you can measure the inside diameter at multiple points to ensure the drum is not out of round and is within specification.

It is recommended to measure the drums every time you inspect the brakes or replace the brake shoes and regularly inspect the brake drum assembly for any signs of cracking, rust, corrosion or uneven friction surface.  At one time it was common to resurface brake drums, however today the more cost effective option is to replace the drums rather than machining them.

Can I replace a brake drum myself?

While replacing the drum can be a bit phsycially demanding, it can be replaced, especially if you're a bit handy with tools.  Tools needed include jack stands and a socket and ratchet to remove the wheel and tire, and either a few bolts or hammer, flat blade screwdriver, torque wrench, and possibly some pliers.  Before tackling anything, jack the rear of the vehicle up and secure it on jack stands.  Then remove the wheel and tire.  Once that's completed, you should be face-to-face with the brake drum, which can either be removed by threading two bolts into the unused holes in the drum, tightening them, and then loosening the bolts to release the drum, or, if your drum doesn't have the empty bolt holes, you can remove the drum by tapping its perimeter with a hammer to jimmy it off. 

While most repairs include the removal of the brake shoes along with the drum, there can be a few circumstances when only the drum needs to be removed.  Regardless, it's a good idea to have a set of new springs on hand in case any need to be replaced.  And if you're going to replace one spring, replace all of them at the same time.  Once the drum is off and you've made necessary changes to other internal components, simply reinstall the drum by inserting it into place and turning it.  You'll know everything is in place if you can turn the drum but still feel a bit of resistance.  Reinstall the wheel and tire, and once you've lowered the vehicle and tightened the lug nuts to your recommended torque specifications, road test the vehicle from 5mph and then 10mph. 

Need a brake drum replacement?

Having properly functioning brakes on your car or truck is an absolute must for your own safety as well as for the safety of others. Since brake drums are an important component of a vehicle’s drum brake system, if they are worn out, then replacement brake drums are needed ASAP. At 1A Auto, we carry a full line of high quality aftermarket brake drums, including both front brake drum and rear brake drum assemblies, for many makes and models.

At 1A Auto, we make shopping for a brake drum replacement for your car, truck, SUV or van easy - we're here to help you select the right part for your vehicle!  We can answer any questions you have about our aftermarket brake drums, warranty, compatibility or to purchase, or you can buy online at 1aauto.com. Restore the safety of your vehicle and order a brake drum replacement from 1A Auto today!