Rear Brakes Grabbing

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Sierra John
Posts: 143
Joined: Tue Sep 04, 2012 1:01 am
Location: Sierra Madre, Calif.

Rear Brakes Grabbing

Post by Sierra John »

When I apply the brakes, the rear end feels like it's crossing rows of uneven railroad tracks. The brakes are grabbing, there's a knocking noise, and the rear end shudders. I have to use the lightest pedal pressure possible. Used to just be when the car was cold. Now, it seems to be full time. What would you suggest checking first? I was wondering if it could be from oil getting on the brake linings.
1966 Town Hardtop
Rt.146
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Re: Rear Brakes Grabbing

Post by Rt.146 »

What year car? 65-66. proportioning valve?
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Sierra John
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Location: Sierra Madre, Calif.

Re: Rear Brakes Grabbing

Post by Sierra John »

It's a '66.
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Cliff Rankin
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Re: Rear Brakes Grabbing

Post by Cliff Rankin »

It’s a long way from my easy chair to your brakes😆 that
Being said...I would pull the drums inspect for leaks and
Make sure everything is free and working , maybe clean
Stuff up with brake clean , quick adjust and back together.
Then a quick bleed 🩸. Ok stop ,if there are any signs of
Brake fluid ( peel the cups a little and look) fix it now.
A tiny bit of rear end fluid you can clean off and try.
This should narrow it down. The brake shoes and drums
Should basically be ok. Let’s get the rest figured out
First. I’ll be watching what you post. Thunderbirds are
My hobby. I work on cars and this is basic brake stuff.
Hope this is helpful.
Cliff
64ZCODE
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Re: Rear Brakes Grabbing

Post by 64ZCODE »

Hi Sierra. Agree with Cliff and would add one more wrinkle, which is that aftermarket brake shoes can result in the chattering you're experiencing. Did you change the brake shoes recently? I ran across this on my '64 when I replaced the front shoes with Centric aftermarket ones after turning the drums. The chattering upon braking was dangerous and frightening. My neighbor who is a long term Ford guy recommended I use Original Equipment brake shoes. After installing those, no more chattering. What I noticed about the OE shoes is the leading and trailing shoes for each wheel are different composition, whereas the Centric ones are same lining leading and trailing. As well, with the OE ones there is a groove cut into the leading shoe, presumably to shed water.

Doug
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Sierra John
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Location: Sierra Madre, Calif.

Re: Rear Brakes Grabbing

Post by Sierra John »

Thanks for all the replies. I appreciate it. The brake shoes have not been changed recently. Every time I have them inspected, they look good and have about 50% to 60% left. The guy I rely on for brake work isn't available for a couple of weeks, so I'll wait until he can inspect it. If the shoes/drums look normal, the proportioning valve could be the issue.
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Cliff Rankin
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Re: Rear Brakes Grabbing

Post by Cliff Rankin »

I think , let’s get to basics. Please keep us updated.
It’s a difficult diagnosis on the form and not being there
And seeing it. I would like to know the out come.
Please post the fix , or if you need to bump heads
Some more , please do so. Always here. Kinda wished
Karl would have chimed in on this. He has a totally different outlook on diagnosis. Love hearing different
Opinions.
Thanks
Cliff
Rt.146
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Re: Rear Brakes Grabbing

Post by Rt.146 »

Sierra John wrote: Tue Sep 22, 2020 6:37 pm It's a '66.

The front being disc brake and the back drum brakes a proportioning valve is used to adjust the pressure between the brake system, it is located on the drivers side inside the engine compartment behind and down from the wheel well. If not scratch on the inside they can be rebuilt, kits are available.
redthundervert64
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Re: Rear Brakes Grabbing

Post by redthundervert64 »

64ZCODE wrote: Wed Sep 23, 2020 7:26 pm Hi Sierra. Agree with Cliff and would add one more wrinkle, which is that aftermarket brake shoes can result in the chattering you're experiencing. Did you change the brake shoes recently? I ran across this on my '64 when I replaced the front shoes with Centric aftermarket ones after turning the drums. The chattering upon braking was dangerous and frightening. My neighbor who is a long term Ford guy recommended I use Original Equipment brake shoes. After installing those, no more chattering. What I noticed about the OE shoes is the leading and trailing shoes for each wheel are different composition, whereas the Centric ones are same lining leading and trailing. As well, with the OE ones there is a groove cut into the leading shoe, presumably to shed water.

Doug
If 64ZCODE is stilled tuned in, can you tell us where you found the "Original Equipment" front brake shoes? I'm having the same problem even after having my brand new drums turned. Thanks.
64ZCODE
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Re: Rear Brakes Grabbing

Post by 64ZCODE »

Sure redthunder, it was a while back but I believe it was from NOS Parts Ltd. If they don't have them they can probably direct you to someone that does:

https://nospartsltd.com/
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64ZCODE
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Re: Rear Brakes Grabbing

Post by 64ZCODE »

I should mention the correct term is New Old Stock (NOS). Also, looks like the NOS Parts Ltd. website is being cranky so best to call them to confirm what they have in stock. I was able to get front and rear shoes for my '64.
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redthundervert64
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Re: Rear Brakes Grabbing

Post by redthundervert64 »

Thanks 64ZCODE - appreciate it!
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Sierra John
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Re: Rear Brakes Grabbing

Post by Sierra John »

Cliff: You wanted to know the outcome with my rear brakes. My brake expert finally checked it out. Everything looked normal. However, the drums have been machined to the max, and the adjustors are turned all the way. Is it possible the knocking I was hearing at the rear when applying the brakes was the adjustor slipping? Everything has been cleaned, so it seems OK for now. If the grabbing and knocking come back, I'll replace the drums and shoes.
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jtschug
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Re: Rear Brakes Grabbing

Post by jtschug »

My rear brakes would grab when my axle started leaking oil into the drum.
Cliff Rankin
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Re: Rear Brakes Grabbing

Post by Cliff Rankin »

I’m sorry for the untimely response. No would not think
So , but it’s possible. I can hear my back brakes when I hit
The peddle and it’s quite in my garage. Glad things
Worked out with a little maintenance.
Thanks
Cliff
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