My 'Cuda wants to lock up and slide way too easy....

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MrJLR

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In the rare event of a hard braking situation, my 68 Barracuda wants to lock the wheels and slide.....
Under normal conditions the brakes are beautiful. .....
Non-power brakes...front stock disk with rear drums...
I'm not "standing on the brakes" either but just pressing harder.
Been driving for 35 years so it's not like I don't know how to use brakes....
My only thought is proportioning valve???

Jeff
 
If it's all 4 than a proportional valve wouldn't help, and your brakes are doing their job. It's a 68 its not going to stop like a new car. Grippier tires will help.
 
If it's all 4 than a proportional valve wouldn't help, and your brakes are doing there job. It's a 68 it not going to stop like a new car. Grippier tires will help.

Better tires might really make a huge difference. ....hadn't thought of that.....
 
Read moparaction.com/discotech. Tech Editor Rick has smaller bore rear wheel cyls. tha reduce the amount of rear brake. And yes, the 108"w.b. cars are worse in this regard than the 111"s.
 
Firstly; Better tires, or bigger tires, or both; then
if power-assisted, shorten the pushrod 1 turn atta time until you get the right amount of assist for your driving style; then
if it is still sensitive, install the next size smaller M/C, for better modulation and feedback.
If the rear tends to lock first or it comes around to pass you, then install the next size smaller rear w/c's, to take care of that.

If you have diabetes, get yourself to the doctor.
 
If the rears are locking first then something is not right. Factory Disc cars of this vintage had a Separate hold off valve down on the frame rail about 16” from the safety/distribution valve. If all is well it should keep the rear from applying hard and let the front discs do the load First! When we went to Carlisle 2019 I had the left rear wheel cylinder pop on the trip while in the trailer. The distribution valve did what it supposed to and tripped the light and isolated the rear brake circuit. Two new rear cylinders are ordered and only 5 years old.
 
The first thing to do is isolate which wheels lock up first and under what circumstances.
The take off the drums in question and look for evidence.
Chances are good something is grabbing.
A shoe that's not square, linings that aren't arced to the drum (tips grab), wrong shoe, etc etc.
Between the FSM and the 1969 Tech on Drum Brakes, there's pretty good factory info on diagnosing.

if the fronts are locking up - then a good chance the pistons are not moving evenly.

My only thought is proportioning valve???
If the rears lock up after the weight has transfered to the front, then yes that's possible.
If you need a review of what proportioning valves do, again Chrysler Tech is a good place to turn.
1967 Chrysler Imperial Disc Brake System From the Master Technicians Service Conference Session 233
 
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