- I keep seeing conflicting information about wether the self adjuster is engaged from driving in reverse and hitting the brake and using the parking brake.
- Also does the self adjuster impact the function of the brake peddle. After adjusting it. The parking brake improved a lot, but it doesn't seem to have impacted the peddle.
if the drum brake fails to adjust itself, it will take more fluid to actuate the brake, and the brake pedal will sink lower and lower to the floor as the brake wears. The automatic adjuster does its thing during normal braking use. Not when using the hand brake. Not only when driving in reverse...
I am still not getting it. I don't see how changing the starting position of the brake pads changes the TOTAL amount of brake fluid required for the pads to hit the drum. It seems to me that the cylinders in the wheel cylinder are going to have a starting position that is further apart as the self adjuster increases, but ultimately the amount brake fluid required is the same.
I am assuming the amount of brake fluid in the system is constant.
This is difficult without being able to post an image, but the adjuster moves the shoes' resting position further outward as it adjusts to maintain a specified gap between the shoe and drum. The master cylinder only needs to send the same amount of fluid to actuate the brake for that certain distance. The slave pistons only retract as much as is required to make that gap, once they do, the adjuster takes the force of the springs off the slave pistons. The fluid level in the reservoir will drop as the brake pads wear down.
The amount of brake fluid is the same, but the amount of brake fluid in between the master cylinder and the rear brake cylinders will vary according to the adjustment of the brake shoes or calipers - shoe closer to the drum = an extended piston = a little more fluid inside the rear brake cylinder.
This is why, as brake pads and shoes wear, the brake fluid in the reservoir goes down a touch every few thousand miles, and requires topping up.
@glen_stet
This would indicate to me that the brakes would work fine even if the self adjuster is not functioning properly.
It's possible that things changed in the intervening years, but on the Wagner and Bendix brakes common on U.S. cars in the 1960s the automatic adjusters worked when backing up. Reverse motion of the brake shoes as they wore down worked a a cable or lever to advance the adjuster via a star-shaped wheel. Pretty much a Rube Goldberg type setup and failure of the self-adjusters was common.
@chucktobias
Pretty much a Rube Goldberg type setup and failure of the self-adjusters was common. -Exactly!
@chucktobias
The difference with this Toyota drum brake is that the adjuster is up underneath the slave cylinder, and the lower shoe pivot point is a fixed anchor, where the Chevy lower point floated freely with the adjuster between the shoes. Toyota still gets the job done, but with the shoes anchored in place, the self adjusting mechanism is actuated differently.