Rear brakedrum self adjuster.

[Sebastian]

Hey all,
I was thinking about self adjusters, previously and after watching Erics latest video.
He was talking about going in reverse and slamming on the brakes to make the self adjuster adjust itself.

I see people writing/saying that all the time, but no one ever has a answer to why you would have to go in reverse to do it.
If you brake, the shoes expand, and if you use the parking brake, they expand and increase the space between them to let the adjuster do its thing.
No matter if its a leading/trailing or a duo servo.

Does anyone have a good explanation for why you would have to reverse for the adjuster to work?

/ risingsbo

Topic

[Wyr Twister]

Best I remember , brake shoes ” shift ” one way when the brakes are applied & the vehicle is moving forward . The ” shift ” the other way when brakes are applied & the vehicle is moving in reverse .

The latter seems to force the self adjuster to work , better .

I have used the back up and hit the brakes , method , many times .

God bless
Wyr

[Charles]

Drum brakes have return springs that pull the piston back in after braking and the shoes rest on the center pin (top of the shoe). When you are moving forward and the brakes are loose the force will be exerted on the rear shoe forcing it to the center pin while the front shoe will be moved by the piston. So when going forward the front piston is extended and the front shoe moves to close the gap between the drum and the shoe.

In reverse the front shoe is rests on the center pin and the rear piston and shoe move to fill the gap between the shoe and drum. When the gap between the drum and shoe is large enough the piston moves far enough to operate a leaver that decreases the amount the shoe can return. The leaver is only tied to the movement of the rear shoe.

[Sebastian]

Ah I see. Thanks for the replys guys.
Have a good weekend!

[Author]

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