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Old 10-09-2017, 05:49 PM   #1
70 shorty
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How much drag for drum brakes?

I've got a pedal that goes close to the floor in my truck. It's a 70 with bone stock 4 wheel manual drums. I want to try adjusting the brakes to see if that helps. I've also noticed some cracking in the front brake hoses, so those will get changed. I know given the cracking the hoses certainly could be expanding. there is no fluid leaking anywhere, or at least not onto the back side of the wheels or tires. Also, what's the best way to balance the brakes? So, in short, I'd like to have the drums performing as good as they possibly can, so any other suggestions are welcome. (No, I'm not doing a disc conversion any time soon)
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Old 10-09-2017, 05:50 PM   #2
70 shorty
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Re: How much drag for drum brakes?

Oh, and one strange thing I've noticed is pedal doesn't go down as far when the truck isn't running. Remember this is a NON power assist truck, so how is that possible?
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70 C10, shortstep, .30 over 250,Hurst shifted 3 spd parts hauler. Holley 390, Clifford Intake, Header, ported cylinder head, unknown bigger cam.
79 Corvette L82, 4 spd, black, red interior, headers, flowmasters, and unkown bigger cam.
96 Jeep Grand Cherokee 4.0 4x4 daily driver, 325K+, still looks and drivers like new-take that Honda and Toyota!
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Old 10-09-2017, 08:04 PM   #3
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Re: How much drag for drum brakes?

time for 100 % brake job
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Old 10-09-2017, 08:17 PM   #4
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Re: How much drag for drum brakes?

I drove 4 wheel drums on a 68 stepper for years without incident. This required regular adjustment and failing components had to be replaced immediately.

After you swap out the bad shoes, bad soft lines and any other components that need replacement, bleed properly and then adjust each corner so that you do have the shoes dragging somewhat on the drums ( wheel should not spin freely, nor should it stop immediately ). Go drive and flog the brakes very hard repeatedly to bring them up to temp and bed the shoes onto the drums well. After they cool off, adjust again. Might take a few cycles of this to get them where they need to be initially after replacing all the shoes/drums.

Make sure your master cylinder plunger isn't allowing fluid to pass by it: attempt to gain more pedal by quickly pumping the brake pedal. If that works, you need a new master.

Hth,

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Old 10-09-2017, 08:24 PM   #5
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Re: How much drag for drum brakes?

You can hear the shoes touching the drums but no drag. Brakes out of adjustment won't affect the pedal that much (unless they were never adjusted from the get-go), even with pads scrubbed off. They self adjust. You have a hydraulic issue
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Old 10-09-2017, 08:29 PM   #6
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Re: How much drag for drum brakes?

My 70 has self adjusting brakes
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Old 10-09-2017, 08:40 PM   #7
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Re: How much drag for drum brakes?

Disk brakes should drag slightly and drums not at all.
At least rear drums have self adjusters and a tang on a lever that adjusts the shoes out as they wear. I seem to recall that they adjust wnen you back up and brake or the same and stop completely.
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Old 10-09-2017, 10:02 PM   #8
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Re: How much drag for drum brakes?

drums dont drag but they must be adjusted , initially, so that they are very very close to the drum surface. then you can rely on the self adjusting features to maintain the proper relationship between drum and shoe
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Old 10-09-2017, 11:01 PM   #9
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Re: How much drag for drum brakes?

Looks like you need to adjust the brakes. That vintage should be self-adjusting, so maybe something else is going on. Cracks in the outer liner don't tell much, but if the flex lines are over 10 years old, I would just replace them. Cracked linings indicate, in general, that the brake shoes have gotten really hot. This can be caused by stopping from high speed quickly (like in drag racing), and will also show evidence of blue spots on the drum faces. Ask me how I know that one. The other possibility for cracked linings is that the springs are weak. If you are going to replace the linings, might as well replace all the springs while you are at it, and machine the drums. You can pop a boot off a wheel cylinder (check 'em all) to see if fluid is leaking past the cups. If so, fix it right. If you don't have the experience, hire it. Brakes are too important.
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Old 10-09-2017, 11:16 PM   #10
CastIron
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Re: How much drag for drum brakes?

Drum brakes shouldn't have any drag. That's one of the reasons they still use them on so many cars. If they are adjusted too loose they will have excessive pedal travel. If the pedal goes to the floor and feels solid, its probably out of adjustment. If it's spongy and goes to the floor, it's probably in the hydraulics. As weq92f mentioned above, pump your brakes and see if they feel better to see if it's in the master cylinder.
Depending on how old everything is, it's probably a good idea to just do front and rear shoes, springs, wheel cylinders and machine the drums. (and possibly a master cylinder)
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Old 10-12-2017, 08:47 PM   #11
70 shorty
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Re: How much drag for drum brakes?

Yeah, the pedal goes pretty close to the floor, but it's solid, not spongy at all. I'm waiting for this crazy humidity to die down, so I hope to dive into this over the weekend. Thanks for all the responses.
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70 C10, shortstep, .30 over 250,Hurst shifted 3 spd parts hauler. Holley 390, Clifford Intake, Header, ported cylinder head, unknown bigger cam.
79 Corvette L82, 4 spd, black, red interior, headers, flowmasters, and unkown bigger cam.
96 Jeep Grand Cherokee 4.0 4x4 daily driver, 325K+, still looks and drivers like new-take that Honda and Toyota!
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Old 10-12-2017, 09:52 PM   #12
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Re: How much drag for drum brakes?

Drum brakes will drag slightly when adjusted properly. By slightly, I do mean slightly. Even freshly turned drums are not perfectly round. They will touch the shoes at least on one spot when rotated.
The shoes should be adjusted and the brake pressed and released to center the shoes. Then spun and rechecked for contact and usually readjusted again.

It is important to re-center shoes after each adjustment. It is also important to check the contact pads on the brake plate. The pads must be clean, rust free and smooth.

Ridges worn into the contact pads will prevent the shoes from returning to center and prevent the proper adjustment.

Ridges are common on these old trucks. Usually it's easy to weld up and grind smooth.

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Last edited by RichardJ; 10-12-2017 at 11:10 PM.
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Old 10-12-2017, 10:57 PM   #13
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Re: How much drag for drum brakes?

Quote:
Originally Posted by special-K View Post
You can hear the shoes touching the drums but no drag.
This, exactly. Can't add anything to this statement other than to agree 100%.
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Old 10-13-2017, 09:41 AM   #14
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Re: How much drag for drum brakes?

often a bad master thats bypassing itself internally will give a good pedal when pressed hard standing still but will drop to the floor with light pressure while rolling
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