70 Road runner, stock 11" drums. Front left continually adjusts looser over time, and fairly quickly. I set it so there is enough drag to get about a turn when I spin the tire, and w/in 20-30 miles it's loose again. More than about 100 miles and it's dangerous, that side is so loose that when I hit the brakes it pulls sharply to the right. Adjust it out and everything is ok.

I just had it apart, and confirmed it is a left hand adjuster. I double checked that everything is connected correctly, and took a pry bar and moved the rear shoe back at the top, and it did click the adjustor. I double checked that it is going in the right direction, i.e. when the adjuster is turned, it is expanding and not contracting.

Had a mopar friend take a look, and he saw nothing wrong either.

What could be causing this?

Is the spring laying against the star so the star doesn't turn from vibration?

Can you post a picture of the star wheel and self adjuster lever?

1970 B-body has self adjusting 11" brakes. First time for this. Mick states self adjuster.

Best picture I have of the layout from the FSM

A picture of the actual brake on the car would be nice.

that is what I would confirm & compare the tang/teeth etc on the adjuster assy on both sides to see if they are identical (other than the mirror images/different twist on the threads). The tang somehow has to be improperly allowing the star wheel teeth to vibrate/move for it to be loosening.

My Dart is doing that, because the spring has rusted, and lost all of its tension allowing the star wheel adjuster to be loose and not in gauge the star wheel allowing it to back off.

Also make sure the adjuster is inserted in place in the proper orientation. If swapped end for end the adjuster cable and plate will turn the adjuster the wrong way, and make the shoes move AWAY from the drums instead of TOWARDS the drums.

Sounds like the adjuster is backakwards

I won't be able to get pictures until this weekend, but I

1) made sure this was a left side adjustor,
2) matched the position of all the components with the diagram in the FSM,
3) turned the adjuster by hand to make sure it was going in the right direction, and
4) then pried the rear shoe away from the perch, and it did move the adjustor, which I once again verified was the correct direction.

doesn't mean I didn't miss something, but I think all of that is good.

Or swapped side for side.....

You are aware that the self-adjusters only work when the brakes are firmly applied when backing up?

Lots of folks shift to Drive after backing up and seldom/never use the brakes.

Yes, that's why I pried the rear shoe away from the top mount. And as mentioned, it worked as expected.

does the spring set down tight against the star wheel?

if nothing appears bent/out of place/not working/wrong parts you might pull the drum & have a helper work the pedal BARELY so the shoes expand a slight bit then let off & repeat & see if the star wheel starts expanding the shoes. work with him so he goes just far enough for the tang to catch the next tooth. Holler what it ends up being.

Keyword here is BARELY, unless you want brake cylinder pistons all over your shop...

Did some stupid things when I was young.... LOL

Many problems on the suggestions so far:

1) the drum needs to be on to rotate the shoes to move the lever. Actuating the brakes with no drum will not show you anything.

You can pry the front shoe forward to see the action of the lever moving the star wheel.

2) There is no spring that touches the star wheel on self adjusting brakes.

3) if the star wheel is in backwards the lever will not touch it, it won't move the wheel backwards.

I blame the star/ cable combo, if the treads are definitely turning in then something is manually spinning the star, is it the correct cable length? for that size shoe?

The adjuster lever is the only thing touching the star wheel. It should be touching 100% of the time. It should be parallel to the star wheel.

If not then the length of the cable could be wrong, or the routing of the cable.

There is a spring that returns the adjusting lever all the way down and tightens the cable when brakes are released. It there a spring present to return the lever down?

Do you have the lever that mounts on a pivot pin through the shoe? Or do you have the lever that just clips in a hole in the shoe?

Mick, look at the FSM picture posted and compare. Show us a picture when you can.

Take out the adjusters and manually adjust them once a year.

Yeah, but is the driver actually using the brakes to stop when backing up?

Might be hunting up the wrong tree.
If the right brake seems to grab hard, then maybe the left brake isn't grabbing at all. Why? Initial adjustment plays a role, but not to extent described.

20-30 miles is not normally far enough to have made a difference in the shoe lining thickness. Normally - if you're coming down Mt Washington at a clip, wear will be higher. :lol:

If the shoes aren't grabbing, then the self-adjusters won't move.
On the '69 up adjusters, adjusters are actuated in reverse as the secondary shoes grab .

Based on what's posted so far, I'd see if the left wheel cylinder can be bled and if the wheel cyl pistons both move free.

Also, review Chrysler's drum brake advice to techs
http://www.imperialclub.org/Repair/Lit/Master/204/Page01.htm

and '69
http://www.imperialclub.org/Repair/Lit/Master/260/Cover.htm

Are the primary and secondary shoes in the correct positions? Not sure if it would cause the issue but I thought I would ask.

So if anyone has noticed, I kind of got sidetracked from the brake issue because I broke the perch that the motor mount sits on clean off of the k frame.

So as I'm taking the whole front end apart to drop the k frame, I did get a chance to take a picture of the brakes. All look good to me, but the first picture is the drivers side, the one that keeps un adjusting.

is the drivers side adjuster left hand thread?,if not thats your problem

Yes it's left hand thread, you can see that in the picture. And yes I checked when I saw the picture.

Why are the backing plate bolts loose in your first picture?

because he just said in reply number #2412931 at 8:44pm;

No need to remove those bolts though

Yep- that threw me - I read his post but no reason to take the backing plates loose -

Ive done it that way several times over the years.
Much easier to do it this way than break the ball joint loose. ( aka no pitchfork tool or BFH required to break the ball joint loose. )

This way the lower ball joint and associated suspension components come out the with the K frame / lower control arms / tie rod ends intact.

And he doesn't have to break lose the brake lines and have to bleed the brakes. Different ways to get the job done.

First pic looks like you have the shoes mixed up.. Isnt the longer shoe supposed to go on the back??

I'll double check, but I think the shoes are on correctly.

Yes, that was the plan...

Is there enough slack in the brake hose to slide the drum backing plate off the spindle?

Might be. If he lifts the arms and spindle up all the way, then it's very possible.

Leave the upper control arm, spindle, and backing plate in the car, no need to remove it.

Take the k frame with lower control arms, lower ball joints and all the steering linkage with it, great plan.

You don't need to bleed brakes, align the front end, bust ball joints and rip the boots.

So this thread seems to have gone a little off track with the k frame removal. what about the brakes? anyone see anything in the pictures, or have any other ideas?

Yes, back the brake problem...



It is super frustrating for such a simple set up to go wrong, isn't it? You are sure the driver's shoes aren't wearing down prematurely, right? Does the car pull left when shoes are adjusted manually?

Otherwise the car pulling to the side when the shoes wear down for lack of adjustment, could be hydraulic pressure isn't split equally... but you'd have pulling to the left after adjustment..

.. so, OK my gut agrees the problem is in the adjuster system.

(to explain - I had a persistent "unequal braking" problem at my rear brakes a few years ago - the adjuster setup looked dead perfect, so I kept thinking it was hydraulic pressure sending unequal brake force to the rears. End of story was I found a very small discrepancy in the actuator arm's position that didn't let it engage the star wheel properly - it was the cable's eye loop at the TOP of the brake drum resulted in a shorter cable length. Problem solved).

Going back to something very basic: I'd remove the rear brake drums which are working FINE (are they wearing equally?) and compare the fronts to the rears.... compare orientation of brake shoes, star wheel, cables, springs, everything.. my gut tells me something very minor isn't right and you have to find it by careful observation of something that DOES WORK right..

Do you have any Mopar buddies with '70 B-body? My '67 and '65 are just a bit different than yours.

Cheers,
- Art

Ages ago I removed all the self adjusters on my Barracuda. The brakes seldom needed adjusting and when they did it was minute and consistent across all of them. This would have been 1994ish and at the time I think wagner had a kit to get rid of the adjusters, came with some springs and maybe an adjuster?

I have since moved to disc brakes on the front and soon the rear.

the setup looks good to me, that star wheel teeth and the plate combo looks worn out, and somethings not right with the primary shoes, it seems like you have 4 secondary shoes

I'd toss the self adjuster stuff & elim the problem (most self adjuster setups dont work good anyhow). You pretty much just need a horizontle spring from shoe web to web to go over the star wheel & bears down on it. adj em till you hear a slight "tick" at one point in the tires' revolution. Up on stands spin the fronts forward by hand & the rears idling in drive (have a helper hit the pedal to stop em & you spoon em up a bit then he lets off & repeat till you hear that slight "tick").

Only diagnostic thing I can think of is to remove the adjuster cable on both sides and see what happens.
If all is good, reinstall the cable, but interchange sides to see if it happens on opposite side. I have no explanation how the adjuster can just back off or shorten. Only designed to go one way and that is to make the shoes tighter to the drum.
Did you pull on the cable to actuate the adjuster? Does it go the right way?
Post a pic of the top half of the offending side or even the entire side.

check brake drum max diameters

Is it really in adjusting or are the shoes just seating in. I'd like to see the wear pattern on the shoes themselves.