Sable V6-232 3.8L (1988)
Brake Drum: Testing and Inspection
VISUAL INSPECTION
Inspect the drum for cracks. If any large, through-the-drum cracks are located the drum must be replaced.
NOTE: Cracks in drums are often difficult to locate. To quickly determine if a drum is cracked lightly drop the drum (from a height of 4-5
inches) onto a flat hard surface. A cracked drum will make a dull thud sound while a good drum will make a ringing sound.
Inspect for signs of overheating. An overheated drum will often be discolored (blue/gold), warped, or heat checked. Heat checks are small cracks
in the drum friction surface. Heat checks can be removed by resurfacing.
NOTE: The cause of the overheating should be determined prior to replacing the shoes/linings or drums.
Inspect for scoring. Any grooves or scores in excess of 0.008 inches should be resurfaced.
SPECIFICATIONS - See: Specifications
MAXIMUM DIAMETER
Purpose
The thickness of the drum friction surface is directly proportional to the drums ability to absorb and release heat during braking. As the drum
becomes thinner due to normal wear and resurfacing it looses its ability to absorb and release heat and is more prone to brake fade, distortion,
and cracking.
As the drum wears the inside diameter of the drum increases. The amount of drum thickness lost to wear is equal to 1/2 the increase in
diameter.
How To Measure
NOTE: For additional information on how to use a drum micrometer see Fundamentals and Basics.
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A drum micrometer is used to measure the drum diameter.
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The micrometer scale should be initially set to the original (new) thickness of the drum.
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The base of the micrometer should be placed in the deepest groove in the drum and held steady while the measuring point is swiveled to find
the maximum diameter.
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The base and measuring point should be kept at the same depth in the drum.
