Brake Hang up

[carfreak6970]

So this is dealing with a B-Body. The car is a 70 charger with 10" drums on all corners. It is running the disk brake booster and a drum master cylinder. The car has only 2,700 miles since it was restored. The car has been on the road since 2017.

The issue I have been having is after driving for 20-30 minutes the car would develop a vibration up front that would scare the hell out of me. I would pull over and check everything and nothing seemed to be amiss. Get back on the road and everything would be back to normal. The other issue is braking would be okay, but have touchy brakes (I chalked that up to being over boosted with the disc brake booster), but there would be a hell of a vibration when braking from 60mph-20mph in highway traffic (got driven in pittsburgh highway rush hour traffic).

I took it to a retired mopar technician that also has a 70 charger and challenger and he took it for a drive. He witnessed what I was feeling and said it had something to do with the brakes. We put it up on his lift and noticed that it was missing the adjustment springs that go below the spindle but above the adjuster. We also notice the left brake was significantly warmer than the passenger. He suggested the brakes are either not retracting due to the springs and/or I didnt adjust the push rod properly when I installed the disk brake booster.

I did find the springs at my folks garage and installed them. With one drum off, I took note of the brake shoes moving out as the pedal was applied and then retracting once pressure was released. however, it appeared the passenger side did not move as much as the drivers side. I put everything back together and took it for a short drive. it still did pull to the left but the brakes didnt appear as touchy. Now I did not drive it long enough to see if that vibration would have came back, but the drivers drum was still warmer than the passengers when I put it back in the garage.

Now I get the push rod being adjusted improperly causing the system to not relieve the pressure, but why would the drivers side be applying more than the passengers side? and what tests could I run to determine why the drivers side is applying more than the passengers side?

 

[Dana67Dart]

IMHO...

1. Check that both cylinders are the same id side to side.
2. Check that the backing plates are not heavily gouged where the shoes ride.( This can cause the shoes to not move freely.)
3. Be sure the adjusters are on the correct side. one has left had threads one right. There was a change to the adjuster function in 69 and if you have a spring IN the adjuster cable they are 69 and newer. No spring and they are 68 and older.
4. 69 and newer lifts up on the adjuster wheel to make it bigger. 68 and older pushes down to make it bigger (I might have that backwards)
5. Are the wheel bearings adjusted correctly
6. Flex hoses new
7. Drums the same ID, one turned way too far and one new could have issues. The arc of the shoe will only touch part of an over or very turned drum, a new shoe and a new drum will have more contact area.
8. Vibration while braking could easily be a out of round drum.

Good luck

 

[Inertia]

Now I get the push rod being adjusted improperly causing the system to not relieve the pressure, but why would the drivers side be applying more than the passengers side? and what tests could I run to determine why the drivers side is applying more than the passengers side?

Don't overlook that the pass side may not be working as well as the drivers side.
Large shoes to the rear, oil contaminated shoes - - what Dana said, lol

Good luck.
Pix of each side might be helpful.

 

[Dana67Dart]

Don't overlook that the pass side may not be working as well as the drivers side

That is a mouth full right there. Most people (myself included) jump to the conclusion that one side is dragging

 

[RedFish]

The lower return springs broke often. The adjust paw was just too thin. Little scar in tempered steel and that hook end snapped right off. I could go out right now and snap a pic of a broken one from left front of my 67 fish.
As for your come and go crazy brakes, my example is red 89 V6 t-bird. Lady brought it back complaining. I drove it a good 14 miles I guess with no problem. "You drive, I ride. Show me."
Sure enough, shaking, then draging brakes. It was a bad booster. Funny though, give it short rest and it drives fine again for a while.
Salesman talked his mother into this used red chicken to meet his monthly target just in time for Christmas. Good luck with yours

 

[Bewy]

[1] A brake sticking on one side could be a sticking wheel cyl.
[2] Occasionally, you get a brake material that is not compatible with the drum metal & you might get a vibration. Change drums or shoes.
[3] When the shoes rub on the drums, they heat up & get touchy. This can happen from out of round drums or [1] or poor adjustment.
[4] Disk brakes require about 50% more line pressure than drums. Hence the 'touchy' feel. If it is too touchy, get a m/cyl with a 1/16-1/8" bigger bore. Bolt on deal. You will also have less pedal travel.

 

[Kendog 170]

I agree with Dana but you could back off the left brake adjustment a little on the warm drum just to see if it helps. IDK

 

[carfreak6970]

IMHO...

1. Check that both cylinders are the same id side to side.
2. Check that the backing plates are not heavily gouged where the shoes ride.( This can cause the shoes to not move freely.)
3. Be sure the adjusters are on the correct side. one has left had threads one right. There was a change to the adjuster function in 69 and if you have a spring IN the adjuster cable they are 69 and newer. No spring and they are 68 and older.
4. 69 and newer lifts up on the adjuster wheel to make it bigger. 68 and older pushes down to make it bigger (I might have that backwards)
5. Are the wheel bearings adjusted correctly
6. Flex hoses new
7. Drums the same ID, one turned way too far and one new could have issues. The arc of the shoe will only touch part of an over or very turned drum, a new shoe and a new drum will have more contact area.
8. Vibration while braking could easily be a out of round drum.

Good luck

They should be the same ordered at the same time from summit racing P/ns DHB-W73609 & DHB-W73609

Interesting about the backing plates, did not think of that. I can check that.

The adjusters are on the correct side. They hit their levers properly and when manipulated with the brake spoon pushing up lengthens both sides.

Interesting to hear about the different styles, didnt know the reason of the change. But both are correct with the spring in the cable

Wheel bearings were set to what the FSM states. Torque nut to 90 in-lbs while spinning the wheel, place star washer with opening over copper pin hole, back off nut until next opening in star washer.

Flex hoses have been replaced at the earliest 2022, with the front wheel cylinders being replaced in 2024.

I am not sure on the diameter of the drums. Never measured them. Wouldnt have thought that would have made THIS big of a difference. But I have the tool to measure them.

I believe one if not all four are out of round. If one or both front wheels were hanging up and heating the drums up, its almost a guarantee that one is.

[1] A brake sticking on one side could be a sticking wheel cyl.
[2] Occasionally, you get a brake material that is not compatible with the drum metal & you might get a vibration. Change drums or shoes.
[3] When the shoes rub on the drums, they heat up & get touchy. This can happen from out of round drums or [1] or poor adjustment.
[4] Disk brakes require about 50% more line pressure than drums. Hence the 'touchy' feel. If it is too touchy, get a m/cyl with a 1/16-1/8" bigger bore. Bolt on deal. You will also have less pedal travel.

My main plan was to convert to disc brakes (the ones I want to do require a 15" wheel size, currently running 14"), but was going to wait until the car needs new tires (about a year or two out now). Which is why I installed the disc brake booster.


I will try the suggestions mentioned here. As well as checking the push rod length. Given that my hoses and cylinders are newish, could there still be a problem with them? anyway to check that? Also no one mentioned the metering block. That was new from inline tube (I am running DOT-5 fluid) when we put the car together initially. Is there anything internal to the meter block that would allow more fluid to flow to the drivers side over the passengers side? The brake lines were also new when the car went together, but I dont think there could be an issue with them(?)

 

[Dana67Dart]

Looks like you covered all my points

They should be the same ordered at the same time from summit racing P/ns DHB-W73609 & DHB-W73609

Agreed BUT you never know. I bought 10x1.75 drums from summit and the drum inside was a 9" or the like and it had a Duralast sticker on the plastics bag they were in. Summit took care of it they have great cust service

Given that my hoses and cylinders are newish, could there still be a problem with them? anyway to check that?

Not really.

Also no one mentioned the metering block. That was new from inline tube (I am running DOT-5 fluid) when we put the car together initially. Is there anything internal to the meter block that would allow more fluid to flow to the drivers side over the passengers side?

metering block (for disk / drum) or distribution block with or without proportioning valve? TYPICALLY drum / drum do not use a proportioning valve, I don't see it having any effect on braking performance other than the rears would not apply as much pressure to the drums as the fronts. And unless they are plumbed wrong, no side to side effect.

Drum/Drum (Distro Block only)

Disk / Drum Distro / prop Valve) before 70?

Disk / Drum (Combo valve) 70? and newer

(I am running DOT-5 fluid)

I don't see DOT 5 causing an issue unless there was DOT 3 in the lines and has chemically gummed up the system. I have heard that its a wives tail about the need to get EVERY drop of Dot 3 out of the system before adding DOT 5. BUT no first hand experiance

 

[Dave999]

dot 3 absorbs water dot 5 doesn't
so if mixed the water in the dot 3 can migrate and puddle...turn to steam and cause brake problem

so in theory if you had dot 3 flushed out with new dot 3 and then flushed through with dot 5 and filled with dot 5 the chances of there being any considerable amount of water in there would be low and you would not have any problems

if you end up with a 20:80 mix of 5-10 year old dot 3 and dot 5 then you might have a water induced problem.

dave

 

[Dana67Dart]

if you end up with a 20:80 mix of 5-10 year old dot 3 and dot 5 then you might have a water induced problem

IMHO...

If you flush a pint or 2 of dot 5 through the system, the amount of Dot 3 remaining would be negligible.

But I do like your cheaper idea of flushing the system with fresh dot 3 before flushing with Dot 5.

 

[carfreak6970]

That shouldnt be an issue. Since day one of getting this on the road (meaning everything in the braking system being new), we ran DOT 5