brakes Emergency/parking brake problems

[Mike Self]

Can't seem to get the parking brake on my '73 to function properly.  Brake shoes are properly adjusted and have reasonable wear.  I know the cables are stretched, as I've had to insert spacer sleeves on the threaded adjustment section so I don't run out of adjustment.  I've also had to cut about 15 mm off the threaded ends so they won't poke holes in the rubber boot.  

 

I've run the adjustments up until the cables are taut when the lever in the full off position, but I (1) can't seem to get full stop resistance in under six or seven clicks of the handle ratchet, even after tightening the nuts 6-8 mm, and (2) with the lever pulled tight and the cable taut, the car will still roll backward even on a slight slope.  

 

Suggestions?

 

mike

Edited June 21, 2016 by mike

[OriginalOwner]

Could be one side is not working well enough individually, I had this problem with my Chevy truck.

 

For a test, put the lever in the full "off" position.

1)  Loosen Up the left cable.

2)  Then pull the right cable as Tight as possible, and then some.  Then pull the lever Up and check to see if that brake, by itself, will lock the wheel from rotation.

3)  Then do 1) and 2) to check the left side cable.

 

On my truck:  by testing each side separately for proper function, I discovered the left side to be non-functional.  Then digging deeper into the left side I discovered a frayed cable.  When replaced, the system then worked OK.

      Turns out the frayed left cable unbalanced the load on the other cable, such that the right-side cable didn't pull as much as expected, even though everything was correctly adjusted in the static position.

 

Cheers,

 

Carl

 

Edited June 21, 2016 by OriginalOwner

[avoirdupois]

7 hours ago, mike said:

Can't seem to get the parking brake on my '73 to function properly.  Brake shoes are properly adjusted and have reasonable wear.  I know the cables are stretched, as I've had to insert spacer sleeves on the threaded adjustment section so I don't run out of adjustment.  I've also had to cut about 15 mm off the threaded ends so they won't poke holes in the rubber boot.  

 

I've run the adjustments up until the cables are taut when the lever in the full off position, but I (1) can't seem to get full stop resistance in under six or seven clicks of the handle ratchet, even after tightening the nuts 6-8 mm, and (2) with the lever pulled tight and the cable taut, the car will still roll backward even on a slight slope.  

 

Suggestions?

 

mike

 

Uh Oh - details.

 

All things being equal - respecting cable lengths - there are four things that jump to mind as an explanation for your parking brake woes.

 

First, the inside diameter of your drums may have exceeded their working limits with other worn parts (<230mm?).  Miles, wear, brake lathe turning . . . over time it is bound to happen.

 

Second, if there is moderate wear on the drum contact area  - this may exacerbate a weak situation if your shoes are also short on friction material.  Remember,  just because the shoes are thick in one area - don't overlook wear or thin portions elsewhere.  I have some drums that have taken on an even, albeit beveled wear pattern.  New shoes would clearly not make full contact with those drums unless they were cut to conform or they develop a similar wear pattern.  Because the drums and conformed shoes work well on an infrequently driven vehicle - that's where they will remain for the time being.

 

Third, some of your shoe retention hardware may have become dislodged.  It doesn't happen often but given the right harmonic convergence, the "W" retention spring or other brake hardware can loose tension or merely pop out of their own accord resulting in abnormal (unsatisfactory) brake action.    

 

Fourth, there is a rear brake component that helps keeps the shoes equidistant - and close to the drum surface.  Realoem uses a generic description ("thrust rod, left and rt."), but whatever you care to call them, they are the objects closest and furthest to the viewer sitting on the dark background of the "dialed up" image below.  Over the years, those stamped steel parts can develop wear where they contact each shoe.  After years of use such, wear can allow the shoes to sit too far from the drum contact surfaces. Aside from replacing these commonly overlooked parts - a few enterprising 02'ers strategically add a little metal with their welders - and this makes marginal drums, shoes and even stretched cables - workable.

 

Along the same lines it is worth noting that brake shoes often appear to be rebuilt using a cleaned up original metal skeleton with newly bonded or riveted linings.  This is not always the case, but over the years the quality control may be lacking so that the metal portions of the shoes, and in particular where they connect with the so-called thrust rods and the oblong holes into which the brake adjuster cams ride - can be less-than-uniform, also resulting in more-than-usual adjustments.  Although there is a logic to the oblong shaped holes that permit the rear adjusters to control shoe position, this too can be altered with a quick use of a mig welder.  Again, this is not necessarily advisable, but where there is a need some will find a way. 

 

 

 

 

 

   

For illustration purposes only.

Edited June 21, 2016 by avoirdupois

[roadhog0]

11 minutes ago, avoirdupois said:

 

 

Third, there is a rear brake component that helps keeps the shoes equidistant and close to the drum surface.  Realoem seems to use generic descriptions (thrust rod, left and rt.), but whatever you care to call them, they are the objects closest and furthest to the viewer sitting on the dark background of the "dialed up" image below.  Over the years, those stamped steel parts can develop wear where they contact each shoe.  After years of use such wear can allow the shoes to sit too far from the drum contact surfaces. Aside from replacing these parts - a few enterprising 02'ers strategically add a little metal with their welders - and this makes marginal drums, shoes and even stretched cables - workable.

   

 

 

I am going to second this right here. I worked on a nice guy's 320i one day who happened to of bought it new many years earlier, but his parking brake was no longer functioning like yours. I checked adjustment first, all the way out, then pulled the drums off to find a 1/4" or so groove worn in where the parking brake lever pushes on the large part in avoirdupois's picture. They are inexpensive to purchase and easy to replace, so I would check those out.