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Old 06-16-2008, 11:43 AM   #1 (permalink)
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reducing drum brake drag

It just occurred to me that drum brakes tend to have an amount of drag that varies from light to moderate to light etc. over time as they periodically adjust themselves. To jack the car up and turn a wheel by hand really points this out.

Ha anyone here come up with a solution to the problem regarding the automatic brake adjusting mechanism setting the brake shoe adjustment such that the shoes drag on the drum?

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Old 06-16-2008, 12:10 PM   #2 (permalink)
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unfortunately that little bit of drag is federally safety mandated and you will never pass a safety inspection without it.
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Old 06-16-2008, 12:54 PM   #3 (permalink)
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Quote:
It just occurred to me that drum brakes tend to have an amount of drag that varies from light to moderate to light etc. over time as they periodically adjust themselves. To jack the car up and turn a wheel by hand really points this out.
My rear drums do not have any noticable drag. Certainly not to where I can detect it with the wheel on. Are you perhaps sensing the intertia of the wheel and thinking that is brake drag?
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Old 06-16-2008, 02:17 PM   #4 (permalink)
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Originally Posted by ttoyoda View Post
My rear drums do not have any noticable drag. Certainly not to where I can detect it with the wheel on. Are you perhaps sensing the intertia of the wheel and thinking that is brake drag?
No, I am referring to actual drag of the shoes on the drum. That drag will be very minimal or even non existent just before the shoes have worn enough for the automatic adjusting mechanism to click a notch. but just after it does that there is often drag.

My experience with this is from my own vehicles and from thousands of vehicles I have serviced etc. (gas station work).

One solution to this problem would be to remove the automatic adjuster levers and then just adjust the brakes manually every so often but that does not appeal to me at all.

To keep disk brakes from dragging, a slight amount of lateral bearing play does the trick as this allows the wheel to wobble left to right forcing the calipers to spread the pads away from the rotor. But drum brakes are of course a completely different design.
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Old 06-16-2008, 02:35 PM   #5 (permalink)
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why they even use drums at all is a total mystery to me , discs are far more efficient and far easier to work on .. with the invention of discs the drums should have been dropped completely.. I don't get it , anything over 30 years old should be discs all the way around.
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Old 06-16-2008, 02:54 PM   #6 (permalink)
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When chevy went back to drums after 4 wheel discs in trucks, the trend of large wheels came around. That is awesome marketing, knowing that brakes only last 10,000 miles on those custom trucks and suv's. It's THE MAN.
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Old 06-16-2008, 05:09 PM   #7 (permalink)
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To keep disk brakes from dragging, a slight amount of lateral bearing play does the trick as this allows the wheel to wobble left to right forcing the calipers to spread the pads away from the rotor.
I disagree with that theory. The square o-rings used inside the calipers as piston seals have enough spring-back that they pull the piston away from the pads. Otherwise, brakes would always drag until the brake rotor turned a few times, and that is demonstrably not the case.

Quote:
No, I am referring to actual drag of the shoes on the drum. That drag will be very minimal or even non existent just before the shoes have worn enough for the automatic adjusting mechanism to click a notch. but just after it does that there is often drag.
If you say so. Regular use of the parking brake is needed in my cars to make the adjusters move. I have not noticed any drag, other than what is in the bearings and the bearing seals.
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Old 06-16-2008, 05:16 PM   #8 (permalink)
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why they even use drums at all is a total mystery to me , discs are far more efficient and far easier to work on .. with the invention of discs the drums should have been dropped completely.. I don't get it , anything over 30 years old should be discs all the way around.
Because it is very easy to incorporate a cable operated parking brake in the design. Disk brake calipers with a parking brake unit built in (subaru used to do this on the FRONT calipers, the [children of unmarried parents]^*) are a pain to rebuild. Regular calipers are a 10 minute job to rebuild if you rush. I would rather do drum brakes than fight with disc calipers with parking brake klude-ons.

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Old 06-16-2008, 11:04 PM   #9 (permalink)
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Originally Posted by ttoyoda View Post
If you say so. Regular use of the parking brake is needed in my cars to make the adjusters move. I have not noticed any drag, other than what is in the bearings and the bearing seals.
My newest vehicle is 14 years old, and that is also when I quit working on cars other than my own. I don't have any experience with anything newer but all cars I had ever known of required applying the brake while backing the vehicle to actuate the automatic adjusters.

There is a simple explano at:
http://auto.howstuffworks.com/drum-brake2.htm

It talks about the reverse braking type and the parking brake type of adjusters. I had never known of the parking brake type before reading your post.
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Old 06-17-2008, 12:06 AM   #10 (permalink)
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I pinned the adjusting wedge so it can't over adjust. also have small stainless steel springs holding the front pads off the disc. i check them often and adjust if needed. in addition i drill a small hold in the wear face of the drum to let out dust which can cause drag. but then i try to drive without using brakes. a set of pads usually last me about 90.000 miles.

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