Rear brakes locking up - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Pont406 · 03-18-2008, 10:16 AM

I have power drum brakes. Brakes work good. At times I forget that I have a drum brakes. Today in stop and go traffic rear brakes locked up during a panic stop. I was doing about 60-65 mph and traffic came to a stop. Rear end went to the right and after correction it went left. Good thing that nobody was in the right lane and I barelly missed a freeway divider.
On the way home I tryed couple panic stops on the open road. At 50 mph and slower no lock up. Only at 60mph and up rear end locks up. Is this a nature of a drum brakes? I want to know before I replaced bunch of brake parts. For now I am going to park it. Thanks

berencam · 03-18-2008, 12:35 PM

Your front breaks might be a little out of adjustment, might try adjusting the fronts out a little and the backs in a little. Other than that your truck is always going to be a little squirrelly on the breaks, especially in the rain.

HoupPhotography · 03-18-2008, 01:07 PM

maybe the anti-lock system in the rear deceided to be lazy & just lock

**Tetdoeuf** · 03-18-2008, 09:08 PM

My rear brakes were locking up too. I changed the rear shoes that were very very thin, it doesn't seem to do it anymore...

Longhorn Man · 03-19-2008, 01:58 AM

in all reality, that is the norm for ANY non ABS vehicle... esp an empty truck.

**El Jay** · 03-19-2008, 12:50 PM

Quote:

Originally Posted by Pont406

I have power drum brakes. Brakes work good. At times I forget that I have a drum brakes. Today in stop and go traffic rear brakes locked up during a panic stop. I was doing about 60-65 mph and traffic came to a stop. Rear end went to the right and after correction it went left. Good thing that nobody was in the right lane and I barelly missed a freeway divider.
On the way home I tryed couple panic stops on the open road. At 50 mph and slower no lock up. Only at 60mph and up rear end locks up. Is this a nature of a drum brakes? I want to know before I replaced bunch of brake parts. For now I am going to park it. Thanks

Sounds pretty normal to me.
Nail the brakes hard; the front end dives & unloads the rear end, so the rear brakes want to lock up.
You have to ease off the brakes, get rear traction, & then come back on the brakes.

Sounds easy in theory, but real hard when you've sucked your nuts way up into your belly, hoping you don't rear end the guy ahead of you!

68caliRat · 03-20-2008, 05:06 AM

I was told by a shop that because I had larger wheels on the back than the front, the wheels turn slower and the brakes had less inertia to stop. Plus like Longhorn man said, an empty truck is easy to lock up, I've never had it happen when I'm loaded.

Longhorn Man · 03-20-2008, 06:53 AM

tire size can cause an imbalance... but it is not very detectible... esp in an old truck that is still way too light in back.

Pont406 · 03-20-2008, 07:48 AM

I dont know. Like I said brakes work so good that sometimes I forget about having 4 wheel drum brakes.
Guy in front of me must of s*** his pants when he saw nice shiny bumper coming up on him fast. I was about to buy an open trailer but now I might have to reconsider it, untill I figure something out about the brakes.

67_C-30 · 03-20-2008, 07:53 AM

Quote:

Originally Posted by Pont406

I dont know. Like I said brakes work so good that sometimes I forget about having 4 wheel drum brakes.
Guy in front of me must of s*** his pants when he saw nice shiny bumper coming up on him fast. I was about to buy an open trailer but now I might have to reconsider it, untill I figure something out about the brakes.

Actually it will probably not do it with the trailer. My '69 C/10 does it I hit the brakes too quick, but it has never done before when I was pulling my car trailer or my 5X8 4 wheeler trailer. I think the the front nose diving and taking the weight off the rear is the cluprit like Andy said. The trailer must keep some weight back there and allows it work better.

Mint68 · 03-20-2008, 09:20 AM

My ex - 71 k10 used to do this, but I could make it do it at about any speed. It never really bothered me so I left it alone. The new owner didn't enjoy it as much as I did so he fixed it, I guess. He said he put a new proportioning valve on it and it helped a bunch.

03-18-2008, 10:16 AM	#1
Pont406 Registered User Join Date: Aug 2007 Location: West Hills, California Posts: 679	Rear brakes locking up I have power drum brakes. Brakes work good. At times I forget that I have a drum brakes. Today in stop and go traffic rear brakes locked up during a panic stop. I was doing about 60-65 mph and traffic came to a stop. Rear end went to the right and after correction it went left. Good thing that nobody was in the right lane and I barelly missed a freeway divider. On the way home I tryed couple panic stops on the open road. At 50 mph and slower no lock up. Only at 60mph and up rear end locks up. Is this a nature of a drum brakes? I want to know before I replaced bunch of brake parts. For now I am going to park it. Thanks Last edited by Pont406; 03-18-2008 at 10:17 AM.

03-18-2008, 12:35 PM	#2
berencam Registered User Join Date: Aug 2007 Location: branson mo Posts: 933	Re: Rear brakes locking up Your front breaks might be a little out of adjustment, might try adjusting the fronts out a little and the backs in a little. Other than that your truck is always going to be a little squirrelly on the breaks, especially in the rain. __________________ 69 chevy c10 350 3 speed manual wood bed build thread here r.i.p. 70 c10 auto 350 build here

03-18-2008, 01:07 PM	#3
HoupPhotography Registered User Join Date: Feb 2008 Location: Phoenix, Az Posts: 1,204	Re: Rear brakes locking up maybe the anti-lock system in the rear deceided to be lazy & just lock

03-18-2008, 09:08 PM	#4
Tetdoeuf Invest in Gold! Join Date: Sep 2007 Location: OC, CA Posts: 69	Re: Rear brakes locking up My rear brakes were locking up too. I changed the rear shoes that were very very thin, it doesn't seem to do it anymore... __________________ John Gold 1970 Chevy LWB Fleet

03-19-2008, 01:58 AM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Rear brakes locking up in all reality, that is the norm for ANY non ABS vehicle... esp an empty truck.

03-20-2008, 05:06 AM	#7
68caliRat Need a bigger hammer.. Join Date: Feb 2007 Location: Escondido,CA. Posts: 280	Re: Rear brakes locking up I was told by a shop that because I had larger wheels on the back than the front, the wheels turn slower and the brakes had less inertia to stop. Plus like Longhorn man said, an empty truck is easy to lock up, I've never had it happen when I'm loaded. __________________ 1968 GMC 3/4 LWB fleetside Custom Camper 2018 Silverado High Country 2500HD Duramax 4X4

03-20-2008, 06:53 AM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Rear brakes locking up tire size can cause an imbalance... but it is not very detectible... esp in an old truck that is still way too light in back.

03-20-2008, 07:48 AM	#9
Pont406 Registered User Join Date: Aug 2007 Location: West Hills, California Posts: 679	Re: Rear brakes locking up I dont know. Like I said brakes work so good that sometimes I forget about having 4 wheel drum brakes. Guy in front of me must of s*** his pants when he saw nice shiny bumper coming up on him fast. I was about to buy an open trailer but now I might have to reconsider it, untill I figure something out about the brakes.

03-20-2008, 09:20 AM	#11
Mint68 Registered User Join Date: Nov 2004 Location: Nebraska Posts: 762	Re: Rear brakes locking up My ex - 71 k10 used to do this, but I could make it do it at about any speed. It never really bothered me so I left it alone. The new owner didn't enjoy it as much as I did so he fixed it, I guess. He said he put a new proportioning valve on it and it helped a bunch.



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