Manual Rear Drum Brake Adjuster and Adjustment Notes              
Feb 2023 R. Kwas, changes on-going [Comments Added]

 

Brake Adjuster Rebuilding
Brake Adjuster Tool Tip

Reference Information
    Manual Adjustment of Rear Drum Brakes
    Cathode/Anode Ratio
    MGS

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Only the very last Amazons had automatic adjusting Rear Drum Brakes.  Most Amazons and pre ~'69 1800s have rear Brakes requiring periodic manual adjustment.  These notes are applicable to those chassis equipped with the Manual Brake Adjuster.

Manual Brake Adjuster Notes:

Adjusters were supplied by brake manufacturer Girling...they consist of a cast alu housing with steel moving parts.  They function well, but in the long run, this is once again a materials combination which is a recipe for galvanic corrosion...and indeed these parts are typically frozen solid after such a long time, aided by their only periodic need for movement when adjusting.  Warning:  If frozen solid, the diminutive 1/4" square adjustment peg can easily be overwhelmed and broken off, if one doesn't know when to quit applying torque...use judgment!...know when to give up trying to persuade a frozen Adjuster to move, BEFORE you distort, or even twist it off! 

As a temporary measure also to help a "long brake pedal" as rear Shoes wear, and until the Adjuster can be removed for some attention, the Handbrake can be pulled up one click at a time to take up a bit of the free play.  See also: Temporary Rear Brake Adjustment Trick

Thankfully, access is good during a Brake Service when Drum is off, so they can be removed, freed up, and rebuilt with generous amounts of graphite/nickel filled Anti-Seize  on the threads and sliding surfaces which will keep them free to allow movement, and prevent them from turning into a "Monolithic Galvanic Structure"...and this only has to be done once...after that, they will remain free to allow manual adjustment of Shoes, even if the adjustment is necessary only periodically!

 


Girling Manual Rear Brake Adjuster. 

 

From Thread:  Brakes here:  https://www.swedespeed.com/threads/brakes.662862/#post-8041639

"...[if] first application the pedal goes down to some level (and is firm), then at the second, and possibly even third pump, it's up higher (and still nice and firm)...this is caused by the volume of fluid displaced by with each pump moving the Rear Wheel Cylinder Pistons out further...this could, and should be done by adjusting the manual adjuster to close the gap and minimize the lost motion. Adjustment is the 1/4" peg on the back side of the Drum Backing plate at the 6 O'Clock position. See: SW-EM Service Notes  If Adjusters are frozen, which they often are due to galvanic corrosion of the alu and steel parts they're made of, the Drums need to be removed to gain access. For this, use ONLY an approved Puller and techniques, see: SW-EM Brake Drum Removal, Inspection, Reassembly Notes..."

[Temporary Rear Brake Adjustment Trick]:   "...need for adjustment can be quickly verified by simply pulling the Handbrake up a click or a few (but before it results in Shoe to Drum contact and makes friction)...this prebiases the Shoes closer in a similar way the Adjuster would so that the first Pedal push brings them into contact. If prebiasing with the Handbrake raises the Pedal...an adjustment is called for...you can even drive around like that before you have a chance to do the adjustment to give better Pedal-feel...no harm done...!"

 


Normal action of Pistons of the hydraulic Wheel cylinders pushes Brake Shoes apart at the top
Lever action of the Emergency Brake Cable pulling on the Emerg Brk Lever also causes Shoes to be pushed apart mechanically at the top
Manual Adjustor, located at the 6 O'clock position, separates the Shoes mechanically at the bottom...but only when free to move!      

 

Brake Adjuster Rebuilding: 

It's not a big deal, until you attempt a simple rear brake adjustment and they are locked solid, but I recommend this treatment of Adjusters as a bit of Preventative Maintenance when performing a Brake Service and access is good while the Rear Drums are removed!  

Frozen Adjuster is removed from Soaking Container with Liquid Wrench,  since removed from vehicle. 


Brake Adjuster removed from Soaking Container since it was placed in there...more than a year ago! 

 

 
Not so pretty when it first comes out of the Soaking Container...1/4" square Adjustment Peg is still undamaged,
that's good(!), and manufacturer Girling is clearly apparent, in the casting. 

Note:  One can try to turn the 1/4" Adjustment Peg when the Adjuster is off the car and being held in a vice, but when they are locked, they are truly locked, and the Peg can easily be distorted or damaged, just as easily as on the car!...it's better to free the Actuating Cam Followers first, then the AC itself, and that's how I proceeded here...

Adjuster is held securely in a vice while some turning force is applied to one of two Actuating Cam Followers (the biggest flatblade screwdriver in the arsenal is well suited for the task, and this driver even has a hex just below the handle, for applying serious torque!).  

 
Even though it has been soaking for more than a year, pistons are well and truly still(!) stuck as good as welded in the alu oxides!  It takes excessive and irresistible force, accompanied by some "Colorful Shop-Language" to finally free the first Follower...and even more irresistible force (drift and 3lb hammer!) to free the second one!  Note that even with effectively a continuous soaking in penetrant, the Follower was bone-dry, exhibiting only rust and-or alu oxides...I guess the Alu oxides are difficult for penetrant to get through...! 

 


Freeing Follower No 2 calls for a drift and 3lb hammer and further use of CSL!

 


When Follower 2 is finally persuaded to move, ineffectiveness of penetrant is apparent!

Why the steel follower, the less anodic of the couple has corroded, can be explained by the fact that it is the smaller mass of the couple and Cathode/Anode Ratio.

Once both followers have been persuaded to turn and are removed, the Actuating Cam is the next subject of irresistible force and CSL...but this must be applied carefully!  It is very possible to distort or even twist the 1/4" end of a stubborn Screw, off, especially when applying torque to only two flats with only an open-end wrench.  Much preferred is applying torque to all four flats! 

The Actuating Cam does not budge and is well and truly corroded into place...but I SHALL PREVAIL!!! 


This is a job for hellfire courtesy of Bernzomatic and MAPP gas...

 

After a couple of minutes of warming, some Kroil penetrant does make its way to the threads, and judicious and ever increasing back and forth with a 1/4" drive socket and matching hex key, the Actuating Cam is able to be freed fully, and without damage to the 1/4" Adjustment Peg.

 

All subcomponents are laid out and inspected.  Other than a healthy dose of corrosion, they are in decent shape and will serve well again...and likely forever, once properly refurbed and lubed! 

All sub-components are wire brushed or scraped or filed, especially the internal running surfaces of the casting, where the steel Followers run, removing all oxides, the growth of which is THE cause of the frozen AC.


Before... and after a few minutes with the wire wheel.  With the angular interface of Actuating Cam, it is clear how turning the Adj Peg IN,
spreads the Followers, which in-turn separates the Brake Shoes. 

Detail of the AC ...really a brilliantly simple and effective design for redirecting the force 90º, applying it to two Followers, and also locking the adjustment in place!  


A closer look at the shape of the conical end of the Actuating Cam.  Four flats act as detents when engaging
the flats of the Followers during Brake adjustment, locking the Adjustment position.  These interfacing surfaces must
be well lubed, and by a lube which stays put, is good in shear, and high temp qualified!  Anti-Seize fits the bill perfectly! 

 

Refurbishing is simply a matter of anointing all components and alu/steel interface surfaces generously with Anti-Seize and reassembling.  Since the A-S will forever keep the dissimilar metal from making direct electrical contact to allow mother nature to do her galvanic thing, this operation only needs to be performed once. 

Actuating Cam is installed through the Housing, and bottomed fully (which will extend Adjustment Peg fully out the other side). 

 
Followers being inserted and in their final position with A-S, fully retracted
and making contact (or as seen here, almost making contact).

 

Rear Brake Adjustor is now ready to serve faithfully for another 50 years! 

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Brake Adjuster Tool Tip:  Even when an Adjuster is well lubed, I dislike "attacking" the Adjustment Peg with a simple 1/4" open end wrench! ...the thought of rounding off the Peg is just too revolting(!), when a 1/4" square drive socket is close at hand!  A 1/4" drive 3/8hex socket with 3/8 drive ratchet drive set up with a 3/8" male hex socket (same as used for working on the M40 Gearbox Hex Bolts!)...does the trick perfectly!

 


SW-EM super Groovy custom Brake Adjustment Ratchet. 

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Links

Brake Notes

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Reference Information: 

Manual Adjustment of Rear Drum Brakes:

When simply touching up the Rear Brake Adjustment a bit, because the pedal has become a bit "longer", simply lifting the car's rear-end at the Differential and using my groovy little 1/4" square adjustor tool, screw IN (CW) the adjuster peg a couple of detents, while turning the Wheel manually.  When the Adjuster binds up the Wheel totally, its time to back off a detent or two...maybe three. Repeat until Wheel locking is just two detents from free rolling.  Notice the detents at 90º intervals, and set adjustments there!  Double check with an application of the Brake Pedal.  Repeat Adjustment as necessary.

When adjusting the rear brakes for the first time after Shoe replacement or or more major brake work, the manual adjustment should be made first, and with E-Brake adjustment backed off...and after Manual Adjusters have been set, the E-brake should then be adjusted.  Since new Shoes will wear in and seat a bit initially, repeat the adjustment sooner if pedal becomes longer as they seat-in. 

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Cathode/Anode Ratio: 

The theoretical electrochemistry of Galvanic Corrosion is well known and simple, but in practice it was found that the amount of each different metal, and their contact area:  Cathode/Anode Ratio, affects the rate and severity of the corrosion action in a complex manner...

Excerpt from: GALVANIC CORROSION  by Stephen C. Dexter, Professor of Applied Science and Marine Biology

[This article is geared towards the marine and seagoing areas, but generally applicable to a great extent.]

 https://udspace.udel.edu/bitstream/handle/19716/186/corrosion.pdf

 

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Does the reader think this Adjuster might be frozen and might benefit from a disassembly, cleaning and lube?


Picture of likely a MGS (Monolithic Galvanic Structure) Brake Adjuster!
 

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External sources attributed.  Otherwise this information is Copyright © 2023.  Ronald Kwas.   The terms Volvo, Girling, and Kroil are used for reference only.  I have no affiliation with any of these companies other than to try to keep their products working for me, help other enthusiasts do the same, and also present my highly opinionated results of the use of their products here.  The information presented comes from my own experience and carefully considered opinion, and can be used (or not!), or ridiculed and laughed at, or worshipped, at the readers discretion.  Warning:  Don't muck around with brakes if you don't know what you're doing!  As with any recipe, your results may vary, and you are, and will always be, in charge of your own knuckles, and future!

You are welcome to use the information here in good health, and for your own non-commercial purposes, but if you reprint or otherwise republish this article, you must give credit to the author or link back to the SwEm site as the source.  If you don’t, you’re just a lazy, scum sucking plagiarist, and the Boston Globe wants you!  As always, if you can supply corrections, or additional objective information or experience, I will always consider it, and consider working it into the next revision of this article...along with likely the odd metaphor, or analogy (see:  CGG!) and probably wise-a** comment. 

 

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