Brakes #1: Rear brake adjusters

To keep myself from getting bored I tend to work on whatever looks interesting at any given time. I didn’t have a lot of time yesterday (5/10/08) because I had to install an old Blaupunkt ‘Frankfurt’ in my wife’s 1972 Fiat 124 Sedan Special and I’m not the best at this sort of thing to begin with. It turned out the dial on the tuner was broken so I had to open up the deck and find stations using a tiny screwdriver to move the guts around then set the mechanical presets with it energized, scary. Now she has 5 choices to listen to and a DIN plug to run an Ipod into. Point of all this: I expected to have at least 2 hours to work on the SS, I ended up with 45 minutes.

When rummaging around looking for stuff to help with the stereo installation I came across the rear brake adjusters in a big zip-lock bag. I poured them out on the bench and squirted them with some WD40 I had on hand. These Girling units are the same as those found on the first few years of Austin Healey 100/3000 roadsters and probably a lot of other stuff that I don’t know about. I wipe down my work bench, get the couple of tools I will need to take them apart and clean them together and get to work.  I need two for my SS but the bag has 4 in it and I might as well do all four at once, preserving the last two for the next project.

The center shaft with the square drive is the adjuster, turn it clockwise to adjust the brake shoes out, anti-clockwise to adjust them in. The damaged threads can be seen about 6 turns down on the nearer stud.

To disassemble these you pull out the two plungers at either end then turn the adjuster all the way in.  I hold the base in a vise and turn out the two plungers with a big screwdriver.  They are not threaded or anything, but the ramp on the plunger acting against the adjuster will push it out as it turns.  They are usually just stuck from grime and grit and come out pretty easily.  Next I unscrew the center adjuster.  All these parts get cleaned in parts cleaning solvent and set aside. There is usually some stubborn staining on the aluminum body so I usually give them a quick brush with a brass bristle brush and maybe a polish if I am in the mood.  The bores that the plungers live in tend to build up a little grime that is hard to get at so I use a brake cylinder hone and some light oil to dress the bores.

One of the cylinders has a damaged thread, seen in the first pictures.  The threads are fine thread M8’s which are an odd size and a die to chase these would be expensive.  I used a little knife-edged file to cut out the bent part of the thread and test the repair with an oiled nut.  When it goes past it smoothly I know it will be OK.

Three of the four adjusters come apart without incident but the plungers in the fourth were really stuck.  I thought for a moment of just throwing it in a box and dealing with it later or never since I only need two but since I had everything in place to deal with it once it was apart I carried on with the dis-assembly.  I chucked it tight in a vise and soaked it with Kroil and went back to cleaning up the others to give it a few minutes to soak.  Next I drove the adjuster out with the plungers in place.  Finally I used a drift and drove both plungers through the holes in one side.  Examining the plungers I notice the edge where the cone of the adjuster presses on the plungers was deformed causing a little hill of metal to stick up into the bore and in forcing them out the hills left corresponding scrapes in the bore.   I use a file to take off the proud edge of the plungers then give the bores a more aggressive cut with the brake cylinder hone.  Once the assembly all moved freely I cleaned it up.

The polished looking part on the ramp face is where the adjuster rubbed against the plunger.  The shiny edge of the cylindrical part is where I filed the proud edge away.

Here is the brake cylinder hone cleaning the plunger bores up.  The fit is not critical, it just has to move easily yet not be loose.

Here are all the parts displayed in an exploded view.  You can imagine the cone of the adjuster acting on the angled faces of the plungers, which move out the at rest position of the shoes so the hydraulic cylinder doesn’t have to move as far for the shoes to grab.

The final step is putting some oil on all the parts, putting the plungers in place and using a rubber band or some wire to keep it all together.  There is a split lock washer on each stud and then a nut.  When I assemble the brakes I will probably add a flat washer to keep the spring washer from chewing the back of the backing plate up.

I think you can buy these adjusters in reproduction through Moss motors or Alfastop but they are expensive.  If you are missing these on your project they can be had on eBay usually for about $25 each for used units needing a good cleaning, or you can drop me a line and I’ll sell you my extra pair if your need is great.  Up next I’ll look at the adjusters that make the shoe faces parallel to the surface of the drum and compare backing plates between Veloce and standard rear brakes.
Click here to go to the next post in this series.

Advertisements

6 thoughts on “Brakes #1: Rear brake adjusters

  1. M8x1.0 dies aren’t exotic and should be available at a shop with a good selection of fasteners (not home depot). I recently bought a couple, and I am certain that I paid $3.99 each for them.

    Now finding stainless nuts in M8x1.0….not easy at all.

    • Jon,

      This post is getting close to 2 years old -I was in Hawaii and wanted to give you guys something to read. I have since found a source for the M8 x 1.0 die. I’ve been using original nuts, replated in zinc where possible.

      Matt

  2. Matt
    Try using paraffin (wax) or a dry lubricant on those plunger bores rather than oil – it doesn’t attract the brake dust and grime.

    • That’s a good idea. My primary concern was what if 10 years goes by and I don’t use them -good to have them not rusty when the time eventually does come.

      Matt

  3. Yhea, but so many extra points from Ms. Giuliettas I bet- WHO ELSE has a vintage Blaupunkt that plays ipod?
    That is love Matt, good fors ya! And more Alfa as well!

    • Thanks Laurence. Have never gotten around to buying the required stuff to make the Ipod work and the presets in the radio broke so it’s stuck on our local rap/hip-hop station which is good for a different perspective and occasional laugh.

      Maybe I’ll see you Saturday.

      Matt

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s