Brake Notes
01/03 R. Kwas

General:  PLACEHOLDER for a terrifically insightful paragraph about vintage Volvo it comes:   Volvo Brakes have always been very good, considering for example, that the Calipers fitted were the same Girling units fitted on 6 cylinder Jaguars of the time.  Before "Upgrading" brakes because one is not satisfied with their effectiveness, it's recommended to return braking function back to how they performed when might just find you wont think so much about upgrading after that!


Special Tools for Tubing
Swollen Brakelines
Unacceptable Replacement Lines
Front Shoe, Rear Shoe
Brake Drum Removal, Inspection, Reassembly Notes
Girling Brake Vacuum Servo

Reference Information:

Red Rubber Grease
ATE Bremszylinder-Paste

ABS explanation by analogy.


Brake Plumbing and Fittings:  When replacing brake system plumbing components, always triple-check to make absolutely certain flare connections are playing with their correct mates, both in flare type and threads!  Mismatching Braking System connections causes leaks or failures which can be disastrous!

  Type 1 is also known as a "Bubble Fare" and Type 2 is the more typical "Double Flare".  
Excerpt from Volvo factory P120 P1800 manual.


Reference Information:

Types of Flares:

Simple Flare - Suitable for low pressure hydraulic systems, like fuel, ONLY!   Not used, or ever to be used on Brake Systems!!

Double Flare - Suitable for high pressure hydraulic systems, like Brakes! Typically used on US, and British vehicles. Used on vintage Volvos.

Bubble Flare - Suitable for high pressure hydraulic systems. Typically used on modern European vehicles, but can also be found on vintage Volvos!


Flare Detail:  From:


Bleeding Hydraulic Brakes:    (When Bleeding, the Rule is:  Furthest from Master Cylinder first, to Nearest to Master Cylinder last!)

Overheard in the Garage:

Mechanic:  Ready...Puuuush!
Assistant:  Bottom!
Mechanic:  Hold!
Assistant:  Holding!
Mechanic:  Release!  ...Puuuush!
Assistant:  Bottom!
Mechanic:  Hold!
Assistant:  Holding!
Mechanic:  Release!  ...Puuuush!
Assistant:  Bottom!
Mechanic:  Hold!
Assistant:  Holding!
Mechanic:  Release!  ...How does the Pedal feel now?
Assistant:  OK!...Daddy, are we done yet?  Can I go to play with Billy? 


Keeping Brake Fittings and Bleeders usable and from becoming one with components they are screwed into...

When encountering a Brake Fitting or Bleeding Nipple which needs loosening for the first time.  Its always a good idea to spray on a bit of penetrating oil, such as PB Blaster, Croil, WD-40 (yes, although I dislike this product in general, and certainly as a long-term lube - which it definitely is NOT, it will work OK for this immediate penetration and lubing need) or even homemade penetrant cocktail of 1:1 ATF and Acetone,  before attempting loosening it....then, break open the fitting with a wrench which acts on as many surfaces of the hex as possible, not simply an open-end wrench which only acts on two (See also:  Special Tools for Tubing). 

Located where they are, Brake hydraulic fittings tend to corrode in place, and that may be exacerbated by having been over-tightened by the last mechanic...and who knows...maybe the only person who ever tightened it was Inge back in 1967. 

Volvo factory in 1967.  Excuse me Inge ...are those steel toed flip-flops? 
Volvo stock photo. 

...of course if the last mechanic to touch the fitting was me, this is not an issue, as I always coat both threads of fitting and tube to fitting interface with graphite bearing anti-seize, and that is my recommendation for all owners. 


Graphite on threads greatly helps with removal, but this is of little help if fitting has become one with tube and the tube twists as one is loosening the fitting.  Graphite between fitting and tube also, prevents these from unifying! 

I have seen concerns mentioned about contaminating the Brake System with grease or graphite, but don't see this as an the first place, I apply it precisely and only onto the Threads, and Fitting-to-Tube-Interface (not from 10 feet away, with a shovel) and not to the conical seal.  In the second place, IF a tiny bit were to find its way into the hydraulic system, it would surely be flushed out upon the subsequent bleeding...I'm not concerned in the least!  


Special Tools for Tubing:  When working on Brake (or even Clutch) tubing, where fittings may be corroded and require maximum loosening torque, using ordinary open end wrenches increases the possibility of rounding off the hex, since the wrench only contacts two flats (and can/might even splay open slightly increasing the risk).  Rounding off the hex can tremendously increase the scope of the job (and amount and volume of "colorful language" in the garage)... 

This is where using special wrenches can really help.  "Flare Nut Wrenches" shown below, have an advantage over the simple open end wrench.  They greatly reduce the likelihood of rounding the hex flats.  The simple style shown on the left works by contacting five flats,  a great improvement, but still being open, there is still some risk of the wrench and operator not having success, so rounding the overnut remains...the wrench on the right is optimal as it opens to allow installing on tubing, then locks closed to prevent splaying open, and acts on all six flats of a fitting.  It also ratchets in the off-direction, helping in tight spaces...the major advantage is being able to be placed onto a tubing fitting, and still acting on all six hex faces!  

Tubing wrench variations.  A simple version on left (the first one of these was probably made when a creative mechanic sawed a tubing clearance slot into a "Box-End" wrench), and on right, a more advanced version which opens, locks closed and even ratchets in the off direction!  Still more variations exist! 


Swollen (Rubber) Brakelines:  

Many have heard of this phenomenon...some may have even needed to deal with it, so pictures are included here.  Symptoms are wheel components (either Calipers or Wheel Cylinders), which remain activated, and making friction even after the Pedal is released, resulting in sluggish performance, the vehicle possibly pulling to one side, steaming hot Discs or Drums (if one insists on continuing to drive), that only release after the corresponding Bleeding Nipple is opened momentarily to release pressure at that corner (another good reason to carry a 7/16" wrench in the Official Vintage Volvo On-Board Tool Kit!)...which doesn't help much, because the issue might very well return next time the Brakes are applied!  ...but at least one can limp home using the Handbrake...and leaving the Footbrake only for emergency stops (this makes the point for always having a well functioning and adjusted Handbrake, and Emergency Flasher!).

Following are pictures of rubber brakelines from a system which exhibited such symptoms, and which was cured of the symptoms after replacement of the lines.  Thanks to Olli B. of the Volvoniacs Forum for the pictures.  As one can see, passage is quite small to begin with, so there doesn't need to be much internal swelling to occlude the line totally...and since the cross-sectional area is a fraction of an inch, the high pressure occurring in the line during Pedal application is enough to overcome the occlusion, but the few PSI necessary to hold the shoes/pads applied after Pedal is released are not...the occlusion acts as a one-way Valve! 

Link to Volvoniacs thread (German):  Hintere Bremse geht fest (Rear Brake holds):

Rubber brakeline with two IDs?, one normal, one internally swollen to decrease ID!

This line was on a 122 from 68/69 production, so the line was probably original to the vehicle. 
Notice "68 SAE" on the line.  Olli reports the lines are from OE brake component supplier:  ATE,
from other identifying marks on the lines.


Unacceptable Replacement Lines:

I've seen replacement lines with preinstalled fittings which have the correct thread, but also an extended unthreaded section at the end.  Where the Original Equipment lines engage the threads fully, as shown below, the replacement fittings do not.  This means that on the replacement fitting, only a very limited number engage...this is unacceptable to me and I don't use these as delivered.

Know your Replacement Brake Lines and Fittings!

Finding the replacement fittings unusable as delivered, I have cut the unthreaded section off the replacement fitting, and used it, after being so modified, when an OE fitting was not available.  When doing this, it is crucial to assure the cut is perfectly square to the fitting, and also 45ļ internally chamfered, as it must press the flare into its seat precisely!  Modifying brake fittings is not for everyone!


Answer to FB posting:  Does anyone know a way to identify the size of the brake cylinders on the rear drum brakes without pulling the drums? Is there just a universal rebuild kit available from someone?

"Rebuild kits are unique to 3/4" or 13/16" if you're not sure (and who would be after 50 years, unless you're name is Irv G), buy both and return the one you don't use...but if you see severe pitting or scratches in bore, replacing Wheel Cylinder is a good idea although they can be honed if damage is only minimal. Remember, if you need to replace Wheel Cylinder, measure length of and buy hard brakeline to have on hand, because you may very well twist off line when loosening overnut, due to corrosion. Thread sizes are NOT American, or metric(!)..ask for British! (Color coded Red by some suppliers.) Before installation, be ABSOLUTELY CERTAIN that overnut thread, length and flaretype match and are correct!!! See:  Brake Plumbing and Fittings for details.  Good Hunting! "


Front Shoe, Rear Shoe...and Brake Shoe Friction Contribution

Volvo rear Drum Brakes are a Simplex, Single Leading Shoe (SLS), modified design.  In the left diagram below, the Standard Simplex Brake arrangement is shown, along with Relative Braking Force contributed by the Leading and Trailing Shoes.  It can be seen that the Leading Shoe contributes most of the Braking Force, because of the "self-applying" characteristic.  See reference:

In the modified Volvo variation of the Simplex design on right,  Leading Edge of Leading Shoe has been cropped, in order to decrease the relative percentage of Braking force contributed by this shoe, evening the Braking Force contribution (and friction material wear) between both shoes.  

The Adjuster allows for reducing lost motion of the mechanism as friction material wears, and/but does not significantly affect relative Brake Shoe Contribution. 

Volvo's modified version of the Simplex Drum Brake design, with Leading Brake Shoe cropped and Adjuster . 


Common saying:  "The shoe is on the other foot."  Volvo saying:  "The short shoe is the leading shoe."


Rebuilding Calipers:  




Brake Drum Removal, Inspection, Reassembly Notes

Link to thread:  Not Matching Brake Shoes

4 PISTON Girling calipers for Volvo P1800/122 [120-130] [1965]

Kwik Tite Wrench video:

Good Reading on Brakes by an MG specialist:
Brake Fluid Level Monitor:


Girling Brake Vacuum Servo: 

Link to a very good presentation showing theory of operation and function, as well as rebuilding details and advice.


Reference Information:  

As it has no author or commercial parties taking responsibility for content, I can't quite figure out if the homepage is some enthusiast individual's, or the least slickest (no pun intended!) commercial homepage ever published, but it has good reference info, useful for when working on vintage Volvo brake plumbing, or even components of the hydraulic Clutch!  The page doesn't really try to sell anything, but it is a good practical collection of the uses and benefits of RRG:


German Brake component manufacturer ATE has a (transparent, not red) equivalent product, compatible with non-silicon based brake fluids:


Additional (almost important) Information: 

ABS:  I love a good metaphor or analogy (as readers of my tech notes and articles may have noticed!) when I saw this, I laughed so hard, I almost spilled my adult beverage!


External sources attributed.  Otherwise this information is Copyright © 2017.  Ronald Kwas.   The terms Volvo, Girling and ATE are used for reference only.  I have no affiliation with any of these companies 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.  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 donít, youíre 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:  ABS!) and probably wise-a** comment. 


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