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#1 |
Where's my beer?
Join Date: Oct 2004
Location: Glen Allen, VA
Posts: 1,768
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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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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. '03 Grand Cherokee Laredo, 4.0 4x4 daily driver. 165K miles, and runs great '08 Tahoe LTZ 4x4 155K |
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#2 |
Where's my beer?
Join Date: Oct 2004
Location: Glen Allen, VA
Posts: 1,768
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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. '03 Grand Cherokee Laredo, 4.0 4x4 daily driver. 165K miles, and runs great '08 Tahoe LTZ 4x4 155K |
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#3 |
Registered User
![]() Join Date: Nov 2006
Location: KINGSPORT,TN.
Posts: 3,035
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Re: How much drag for drum brakes?
time for 100 % brake job
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I BELIEVE IN JOHN 3:16 |
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#4 |
Registered User
Join Date: Oct 2016
Location: Dallas Texas
Posts: 3,090
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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, -klb
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67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold |
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#5 |
Special Order
![]() ![]() Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,859
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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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"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ Last edited by special-K; 10-10-2017 at 07:43 AM. |
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#6 |
Registered User
![]() Join Date: Nov 2006
Location: KINGSPORT,TN.
Posts: 3,035
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Re: How much drag for drum brakes?
My 70 has self adjusting brakes
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I BELIEVE IN JOHN 3:16 |
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#7 |
Registered User
Join Date: Jun 2013
Location: Somewhere
Posts: 3,076
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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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#8 |
Registered User
Join Date: Dec 2009
Location: bisbee, arizona
Posts: 1,529
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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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#9 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,396
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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.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#10 |
Registered User
Join Date: May 2013
Location: Oregon
Posts: 327
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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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#11 |
Where's my beer?
Join Date: Oct 2004
Location: Glen Allen, VA
Posts: 1,768
|
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. '03 Grand Cherokee Laredo, 4.0 4x4 daily driver. 165K miles, and runs great '08 Tahoe LTZ 4x4 155K |
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#12 |
Registered User
Join Date: Apr 2010
Location: So Cal
Posts: 1,437
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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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'67 GMC 2500, 292, 4spd, AC Last edited by RichardJ; 10-12-2017 at 11:10 PM. |
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#13 |
20' Daredevil (Ret)
![]() Join Date: May 2003
Location: Jefferson State
Posts: 13,628
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Re: How much drag for drum brakes?
This, exactly. Can't add anything to this statement other than to agree 100%.
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- Mike - 1972 K20 LWB 350/350/205 RIP El Jay |
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#14 |
Registered User
Join Date: Apr 2011
Location: formerly NY currentlyNC
Posts: 390
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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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1970 short step c10 leaf spring 454 |
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