Brake Adjuster - How Drum Brakes Work - Auto | HowStuffWorks

• Science
• Tech
• Home & Garden
• Auto
• Culture
• Health
• Money
• Animals
• Lifestyle
• Entertainment

• Quizzes

Submit Search Sign up for our Newsletter! Mobile Newsletter banner close ​ HowStuffWorks Newsletter Mobile Newsletter chat close Mobile Newsletter chat dots Mobile Newsletter chat dots Mobile Newsletter chat dots Mobile Newsletter chat avatar Mobile Newsletter chat subscribe Prev NEXT

Advertisement

HowStuffWorks Auto Auto Parts & Systems Brakes Brake Types How Drum Brakes Work Prev NEXT By: Karim Nice

• Share Content on Facebook
• Share Content on LinkedIn
• Share Content on Flipboard
• Share Content on Reddit
• Share Content via Email

Brake Adjuster

­ ­For the drum brakes to function correctly, the brake shoes must remain close to the drum without touching it. If they get too far away from the drum (as the shoes wear down, for instance), the piston will require more fluid to travel that distance, and your brake pedal will sink closer to the floor when you apply the brakes. This is why most drum brakes have an automatic adjuster.

Now let's add in the parts of the adjuster mechanism. The adjuster uses the self-actuation principle we discussed above.

Advertisement

As the pad wears down, more space will form between the shoe and the drum. Each time the car stops while in reverse, the shoe is pulled tight against the drum. When the gap gets big enough, the adjusting lever rocks enough to advance the adjuster gear by one tooth. The adjuster has threads on it, like a bolt, so that it unscrews a little bit when it turns, lengthening to fill in the gap. When the brake shoes wear a little more, the adjuster can advance again, so it always keeps the shoes close to the drum.

Some cars have an adjuster that is actuated when the emergency brake is applied. This type of adjuster can come out of adjustment if the emergency brake is not used for long periods of time. So if you have this type of adjuster, you should apply your emergency brake at least once a week.

Previous 1 2 3 4 … 5 6 Next Page ​ Cite This!

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

Copy Karim Nice "How Drum Brakes Work" 18 August 2000.HowStuffWorks.com. <https://auto.howstuffworks.com/auto-parts/brakes/brake-types/drum-brake.htm> 30 December 2025 Close Print | Citation More Awesome Stuff

Advertisement

Advertisement

Advertisement