What causes uneven shoe wear on drum brakes?

Through years of use, or lack of lubrication, backing plates can wear. Wear creates grooves and cause the brake shoes to bind and apply unevenly. This will diminish braking on the rear and often show up as warped brake drums or front brake problems. Worn backing plates often have to be replaced.

How do you know when drum brake shoes need replacing?

Technical Bulletins

  1. Inconsistent brake pedal feel. If the rear brakes are drum brakes, the driver may feel vibrations under braking.
  2. Hand brake feels loose. If the hand brake requires a hard yank to keep the car from rolling off, chances are the brake shoes need replacing.
  3. Scraping noise while braking.

Do drum brake shoes have a wear indicator?

Many drum brakes have an external brake shoe wear indicator. Apply the brakes fully and make sure the indicator is in the specified zone. The brake shoes should be replaced if the indicator exceeds the wear out marking on the brake panel.

Do drum brakes work with brake shoes?

Many drum brakes are self-actuating. As the brake shoes contact the drum, there is a kind of wedging action, which has the effect of pressing the shoes into the drum with more force. The extra braking force provided by the wedging action allows drum brakes to use a smaller piston than disc brakes.

Can bad wheel bearings cause uneven brake wear?

Severe looseness related to a worn or damaged bearing can cause excessive runout, leading to uneven wear on the brake pads and/or rotor.

What is a duo servo drum brake?

The duo servo type features a structure where two brake shoes, called the primary shoe and secondary shoe, are linked via an adjuster. Strong pressure from the servo effect (self-boosting effect) of the primary shoe is transmitted to the linked secondary shoe, thus generated a very large braking force.

How many miles do brake drums last?

about 200,000 miles
The brake drums on your car are built to last for about 200,000 miles. In some cases, the drums will wear out sooner due to worn out internal components that put more strain on the drum. As your brake drums begin to wear down, they will actually become smaller.

What are the disadvantages of drum brakes?

Drum brake disadvantages

  • Excessive heating can happen due to heavy braking, which then can cause the drum to distort, and thus cause vibration under braking.
  • Under hard braking, the diameter of the drum increases slightly due to thermal expansion, the driver must press the brake pedal farther.

Do any cars still have drum brakes?

Modern lightweight cars still have rear drum brakes since the majority of the stopping work is done by the front brakes. Although perceived as “ancient”, drum brakes are sufficient for everyday driving and are easier to produce. Previously an engineer in an automotive manufacturing company and a highway concessionaire.

Why do my brake shoes keep coming out?

The wheel cylinders push the shoes out against the drums. The primary piston in the wheel cylinder could be stuck. The backing plates, may have contact point grooves, affecting the brake shoe movement. The drums should have been machined, at the time of brake shoe replacement.

What to do about uneven brake shoe wear?

I recommend having your vehicle’s uneven brake shoe wear be diagnosed and repaired by a certified technician, such as one from YourMechanic. The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

How can I tell if my brake drum is wearing out?

Closely check wear patterns on the friction surface inside the drum. The maximum allowable brake drum diameter is stamped or cast into the outer edge of the drum. Place a brake drum diameter gauge inside the drum. Take several measurements within 90 degrees of each other at the open and closed edges of the drum’s friction surface.

How does a non servo brake shoe work?

Servo design (lower part of shoes move side to side) and the secondary (rear) brake shoe does most of the work. Non-servo design (lower part of shoes fixed) and the primary (front) brake shoe does most of the work. The wheel cylinders push the shoes out against the drums. The primary piston in the wheel cylinder could be stuck.