Originally Posted by rjolly87
Unfortunately our drums do not adjust that way. They adjust on their own with moderate application of the brakes.
Re: How do drum brakes self-adjust?
The self-adjusting brake mechanism consists of an actuating link, adjuster lever, adjuster lever return spring, override spring and override pivot.
The self-adjusting brake mechanism operates only When the brakes are applied while the car is moving rearward and only when the secondary shoe moves a pre-determined distance toward the brake drum.
As the car moves rearward and the brakes are applied friction between the primary shoe and the drum forces the primary shoe against the anchor pin. Hydraulic pressure in the wheel cylinder forces the upper end of the secondary shoe away from the anchor pin. As the secondary shoe moves away from the anchor pin, the upper end of the adjuster lever is prevented from moving by the actuating link. This causes the adjuster lever to pivot on the secondary shoe forcing the adjuster lever against the adjusting screw sprocket. If the brake linings are worn enough to allow the secondary shoe to move the pre-determined distance, the adjuster lever will turn the adjusting screw sprocket one or two teeth, depending on lining. wear. If the secondary shoe does not move the pre-determined distance, movement of the adjuster lever will not be great enough to rotate the adjusting screw sprocket.
When the brakes are released, the adjusting lever return spring will move the adjuster lever into the adjusting position on the sprocket.
An override feature is built into the self-adjusting brake which allows the secondary shoe to be applied in reverse in the event the adjusting screw becomes "frozen" preventing the self-adjuster from operating.
When the car is moving forward and the brakes are applied, the upper end of the secondary shoe is forced against the anchor pin due to the selfenergizing action of the brakes, and the selfadjuster does not operate.
I borrowed this from another site as apparently I'm afflicted with "CRS"
2004 Bonne SLE
1971 Chevelle SS