Types of Drum Brakes
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- เผยแพร่เมื่อ 9 ก.พ. 2025
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Drum brake systems are categorized as either a duo-servo or non-servo type setup. In this video, we discuss the difference between these setups and how they operate.
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Duo-Servo Systems:
Duo-servo brake systems are also known as primary/secondary drum brake systems. This is because there is a primary shoe and a secondary shoe. The primary shoe has less friction material than the secondary shoe. The primary shoe should be installed in the front, and the secondary shoe in the back.
In duo servo systems, the shoes link at the top at an anchoring pin and at the bottom at the self-adjuster. When you press the brake pedal on a duo-servo system, the hydraulic pressure from the wheel cylinder pushes the upper parts of the shoes outward. The primary shoe makes contact with the drum first, and the rotation of the drum tries to pull the shoe downward.
This energy causes the primary shoe to push against the adjuster. The adjuster then forces the secondary shoe outward against the drum. The combination of this outward movement and the rotation of the drum causes the secondary shoe up against the anchoring pin. This cause the shoes to bind against the drum and stops it from rotating. Therefore, the secondary shoe provides the majority of braking power.
Non-Servo Brake Systems
The difference between duo servo and non-servo systems is that the anchoring pin is on the bottom. This means that the application of one shoe has no effect on the other. In non-servo systems, there is a leading shoe and a trailing shoe. The leading shoe is the shoe that moves in the direction the drum is moving. Thus, the leading shoe changes depending on whether you are in forward or reverse.
In either case, the leading shoe provides the majority of the braking force. The rotation of the drum causes the leading shoe to apply with greater force than the trailing shoe.
I'm reading about duo servo brakes but I can't fully get how it works. This video explained well the operations. Direct to the point and no other useless talk.
Thanx for clearing for me for my State Exam! You explained the best and most efficient possible :)
Thank you for explaining the difference very clearly I’ve been studying on this and couldn’t really wrap my head around the duo servo style, now I get it! Thanks!!
I have been looking for a good explanation of this a long long time! Thank You for a simple, easy - common sense rundown :-)
Thanks boss, you saved my day, today i was having a PPT regarding this only and you saved me from failing
💗💗💗🤚🤚🤚🤚
Very well explained,thanks.
That is most clear explanation I've ever seen.
Excellently explained.
Thank you for explaining it the way you did, makes so much more sense now!
My dad showed me this when i put the brakes on backwards and i never forgot this, thanks dad!
I need teachers like this ❤️
Great explanation. Clear and easy to understand. Thank you.
Thank you so much.
I am from Brazil, owner of a 1982 Chevrolet Opala (interesting car made with the Opel Record C and some mechanical features from the Impala).
I have read about de self servo effect, but there was no CLEAR explain about what it is or how does it work.
Your video, words and teaching is amazing.
Now I know it crystal clear and you deserve the credits.
Straight to the point and well explained 👍
Excellent explanation Video.
Really helps when learning auto for the first time.
great video! all info no bs! and explained very well, thank you sir!!!
great video so many how to videos but non mention this, the hard part is determining what is the leading shoe on trailing brakes.
1:52 Leading brake shoe
Very well explained
Perfect explanation!!
Great presentation
Very good explanation thank you
Such an insightful video! Thank you!
Well explained thank you
Well explained!
Perfect explanation! TYVM!
thank you. i figered it out when i tried to write the diffrernce bwtween non duo and duo. cheers
Thank you so much... cleared my doubt
Wow never noticed any car with 8 lugs until now. Nice explanation by the way. There is another type called the dual leading system.
Thank you very much for the video !!!
Best video😍😍🤤
Good info
thank you
Appreciate you!
which one is superior for better and more consistent braking performance? or easier for maintenance ?
But why is the primary shoe still have to be smaller than the secondary shoe on the duo servo setups?
Is there any advantage to either type?
There's a lot of math behind it, but with duo-servo brakes you can have a lower actuator force to get the same amount of braking torque because there's a higher "brake factor" which is essentially like a braking force multiplier. That being said, I honestly don't know if there's a reason why a manufacturer might choose a non-servo over a servo.
Was finding out types of breaks of drums(instrument) i found this instead
POG
Can you please be the first to go over the initial adjustment of a duo servo system ? Non servo, make it drag a bit when you assemble it, no problem. But I'm having grief with my overhaul of the duo servo, with even small drag, the brakes put themselves on. I set it as loose as I dare then drove it just one mile and came back with brakes very hot ... what is it I don't know ? I can assure you I have it all back together correctly and hand brake is set super loose.