How a Battery Functions

Drum Brake Introduction

All of the drum brakes (including parking drum-brakes) which are used on vehicles are of essentially the same design, therefore, their service procedures are almost the same.

NOTE:

• Never apply the service brakes or the parking brake after a brake drum has been removed as either the brake shoes or other connected parts could spring out in a dangerous fashion.
•  After performing inspection and replacement operations, always check that the service brakes and the parking brake are functioning correctly.

Drum Brake Inspection

Removal of a Brake Drum

Release the parking brake before removing either of the brake drums.

For instructions on the removal and reinstallation of brake drums, refer to the section titled “Rear Suspension” in shop manual. shop manual for certain vehicle models only illustrate a procedure for brake disc removal, however such a procedure – with the exception of caliper-related operations – may be applied in the removal of brake drums.

Brake Drum Inner Parts

Whenever a brake drum is removed, its inner parts must be inspected in accordance with shop manual. After checking the wheel cylinder for leaks, clean the inside of the drum using a vacuum cleaner and brake cleaner (degreaser).

Brake Linings

Measure the thickness of each brake lining using a vernier caliper. For accuracy, remove the shoes from the vehicle and take measurements at four points on each lining – that is, two points width-wise near the leading edge and two points width-wise near the trailing edge. If the extent of wear at any point exceeds the service limit, replace both of the shoes together.

If any part of the lining has cracked, is unevenly and/or considerably worn, or shows signs of seizure, it must be replaced regardless of whether or not its thickness is within the specified service limit.

Brake Drum

Measure the inside diameter of each brake drum using a vernier caliper, taking measurements in two directions at 90 degrees to each other. Be sure to take these measurements on the shoe contact surfaces.

Even if internal diameter measurements are within the specified service limit, any drum which is scratched or unevenly worn must be replaced.

Drum Brake Replacement

Incorrect assembly of brake drums and/or shoes may result in dragging or other incorrect brake operation. It is, therefore, crucial that assembly is performed correctly in accordance with shop manual. Please refer to shop manual for details on brake-shoe reassembly procedures.

The following precautions must be observed when reassembling drum brakes:

• The two different types of grease which are used in the reassembly of drum brakes must not be mistaken for each other.
• Never apply grease to brake linings or to the inside surfaces of brake drums. Any grease in these areas would severely compromise braking performance.
• Before installing new brake shoes, ensure that the adjuster bolt is screwed in sufficiently to shorten the adjuster.
• If any shoe has worn beyond its service limit, replace both of the shoes for that wheel. (Note that whenever a shoe becomes worn beyond its service limit, the shoes for the other drum brake will also be approaching their service limits; consequently, it is sensible to replace all four shoes at this same time.)