View topic - front brakes 1961 Desoto locking up when coming to a stop

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PostPosted: Thu Mar 16, 2017 8:50 pm 
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Joined: Mon Feb 27, 2017 4:13 pm
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Front passenger side brake shoes lockup when coming to a stop. The following has been done to the brake system.
Power assist unit rebuilt
New master cylinder
All new cylinders
New drums in rear
New shoes in front
Had all 4 drums turned

Any suggestions?? I'm a new club member my name is Lou.


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PostPosted: Thu Mar 16, 2017 9:19 pm 
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Joined: Fri Jan 30, 2015 10:57 pm
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Make sure your lines are bled properly and your brake shoes are adjusted properly. Otherwise you may have a wheel cylinder leaking coupled with moisture on the linings. This creates lock-up big time.

I'm only going from my experience and others might have different ideas.

"It's delightful, it's delovely, it's DeSoto"


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PostPosted: Sun Apr 30, 2017 2:59 am 
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Joined: Mon Jun 29, 2015 5:19 pm
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Location: Ann Arbor, MI United States
Hi Lou,

Did you ever get this condition resolved? Fred is absolutely correct when he says that adjustment is critical. There is a special service tool required to adjust those brakes, and if it isn't used when new shoes are installed, lockups will frequently be the result. This might be your problem.

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Brent Jacobsen
Owner of a 1952 Desoto Firedome


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PostPosted: Wed May 10, 2017 1:32 am 
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The attached may help. I'm not a '61 expert but I think the brake design is similar to the attached technical info.

Another tip I've seen work is to have the shoes ground to match the machined drums so you have full contact. Need a good brake shop with old machines to perform this work.

Mark


Attachments:
Center-Plane Brakes.pdf [910.34 KiB]
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PostPosted: Sun Jun 04, 2017 1:09 pm 
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Never got the front brake problem resolved. Took them apart, checked the
The cylinders for leaks. Adjusted the brakes and will still lock up once I while
. Have not taken the brake shoes off yet to have them grind down.
Kind of frustrating situation..


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PostPosted: Mon Jun 05, 2017 12:51 am 
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Joined: Mon Jun 03, 2013 10:01 am
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Collapsed brake hose. Did you replace them when you did the brakes ?

Did you adjust the push rod on the brake pedal ? If so, the brakes may always be partially on, and may not release when you take your foot off the pedal. Never mess with that adjustment.

Ron


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PostPosted: Tue Jun 06, 2017 11:41 pm 
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I replaced all the brake hoses and had the power booster rebuilt.
I don't if that push rod was adjusted at that time.


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PostPosted: Mon Aug 21, 2017 8:31 pm 
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Lock-up is very common on center plane brakes, especially on cars that aren't driven regularly. The drums get a bit of surface rust and BOING, lock-up. You can turn the drums, but really just need to clean the rust off the inside with some sandpaper. Also, you could just expect lock up the first time or 2 you apply the brakes, so do it on your terms. Once the brakes scrape the drums a few times you should be good to go.


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PostPosted: Mon Dec 04, 2017 2:00 am 
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Joined: Mon Jun 29, 2015 5:19 pm
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Location: Ann Arbor, MI United States
Lou,

There is a lot of good advice here from people who have experienced the same condition you are experiencing. Every post here brings out good information. This thread makes good reading for anyone owning a Desoto built after 1946 when the Lockheed twin-piston front brake design was used.

One probable cause I haven't seen discussed is friction material. All DeSotos were originally built with brake shoes using asbestos in the friction material. This gave very consistent performance wet or dry, hot or cold. But with the mesothelioma lawsuits of the 1970's and 1980's, asbestos use in friction material stopped (and for good reason). The replacement materials were of two general types; metallics and organics. Neither one stops like asbestos shoes did. Metallics are harder, have higher pedal efforts, and tend to score drums. The organics generally tend to be hygroscopic, that is, they absorb moisture which makes them sticky- hence grabbing brakes. Anyone owning an old car who has had their shoes relined after 1980 is subject to this. The cars with smaller diameter and wider drums, as well as those with twin-piston front brakes seem to be most affected- that would be Chrysler cars made between 1957 and 1962. In 1963 Chrysler went to the Bendix "floating heel" brake design with self adjusters

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Brent Jacobsen
Owner of a 1952 Desoto Firedome


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