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This is the season for heater valves not exercised from cold to hot a few times over the alleged summer, to disintegrate on first use. But that's not what this is about.

Whilst contemplating the brakes prior to replacing all flex-hoses with new and braided type, not knowing how old the ones on the car are, and six or seven years, being, cautiously the life of such parts. And with an aftermarket dual-circuit master-cylinder conversion not just desirable on the HB, but considered essential and inevitable, I dwelled, not for the first time, on the inefficiency of the rear Girling 8x1-1/4 drum brakes, finding them below ideal or possible potential, either by foot-brake or handbrake operation. Compensated for, just, by respectable discs and trouble-free so-far Lockheed calipers on the front.

The rear wheel-cylinder and/or pistons stick contrarily - sometimes in, sometimes out - even a short time after renewal of them. Worn drums, shoes or under-adjusted brakes make this more likely as the piston extends further out than it ought. Uneven and accelerated bore or piston wear is likely if the brake shoes do not contact dead-centre of the piston. If far off to the inside edge as pictured (or the other, outer edge), the piston is unhappily rocked sideways in the bore.

Wear to the backplates presumably has caused the round extensions the outer-edges of the shoes rest and slide upon, to recede. The friction surfaces of the shoes aren't just too far in towards the backplate, but have a sloping attitude due partly to the action of the return springs, they're almost conical in outline, that the innermost end of the shoes is nowhere near the drum when the outermost is touching. The shoes are not parallel to the drum along the width of the contact area, at rest or in brake operation.



Up with this I cannot put!

After giving the wire-brushed backplates a several hour long phosphoric acid gel scrub and rinses with old thinners, followed by Kurust, time to cure and dry, then a coat from an aerosol of red primer, they looked a fright!


Some washers 1.7 mm thick were stuck on with copaslip purely for photographic purposes to illustrate the plan in mind.


A more permanent and robust means of attachment was needed: welding. The welds and splatter then being ground back with a flap disc till almost flush with the added washers.


With the backplate scrubbed up again with a wire-brush front back and sides, more vivid red paint was sprayed in the general direction of the things, all-around. On a warm day with a light breeze, some hours later -the longer the better - this paint dried enough for reassembly. A more durable top-coating followed.


On attempting to fit the drum, at either side of the car, the previously carefully set adjusters had to be retracted five or six clicks, all other things being the same, simply to get the drums on and free running.

A result perhaps. I'd estimate there's a 15-20% improvement in rear brake performance, and the dubious handbrake too is much improved and now a stalwart anchor.

The washers were about 1.7mm thick, the still raised area of the welds left are maybe proud about 0.8mm, so 2.5mm in total of outward shoe edge movement away from the backplate has transformed the rear brakes and the shoes are not so far off-centre in contacting the piston (but still not perfect, I should have used 2mm washers). I'll review them after some miles and bedding in, but the pistons I hope will be less prone to sticking.

I see you have fitted the shoes differently from the first image, (opposite side) fitting both the leading edges at the same point, is this the corrected way? generally the leading edge is at opposite ends and points in the direction of rotation, but i have come across vehicles fitted as your last pic.
I would also add that the cylinder looks like the sliding type which is best fitted lightly greased and free to move for and aft if not it would also contribute to pistons getting stuck.

You're right one of the shoes is not as per the photographs in the manual. I swapped the shoes over in each drum before this most recent overhaul, as the slot the handbrake lever goes into was showing signs of wear, the source along with the lever itself wearing, of the dusting of iron-filings shown in the earlier pictures, and the lever itself was wearing in ridges against the shoe slot too, so I filed this level again a while back. The opposite slot was unused and unworn, it seemed like a good idea at the time. This puts both linings at the top, it doesn't invalidate the improvement as they've been in that way since early this year. I'll probably go back in and correct that by swapping them with the other side of the car or put another set in there, but these have lots of life left.

The cylinders slide easy in the backplate, the pistons themselves however were sticking in short order even on newish wheel cylinders. I'm hoping that centering the shoes on the pistons will help, it just sticks out as wrong, instinct alone tells me. It could also have been gunk breaking off the insides of the flex-hoses contributing to this frequent sticking too: the system has been drained out completely several times in recent years, but the most recent fluid removed, that has only been in there six months or so was contaminated heavily with fine black material in suspension, when I expected it to be fairly clean. Most of the hard pipes I've not long ago replaced. With the hoses replaced that is another possibility and likely source of this material and a general concern eliminated. Hence the recommendation to ruthlessly discard aged flexi-hoses as a matter of routine. Slight radial eccentricity of one of the drums is suspected too, not detectable throbbing in the pedal like say a warped disc would be, but on garage rolling road equipment is shown graphically. The drums really need replacing with new to get everything back to original or better than original specification and performance. Some second-hand drums I'd acquired were worse than those I already had!

Appeciate the correction and your, and others input. It's a dangerous world out there and now is the time to get stuff done before the winter. Continuing the winterisation theme, I've also been using rain-x products one for exterior and another type for interior glass, as the single-speed and no intermittent wiper continues to bug hell out of me, and I've developed a condition called wiper-switch thumb. Another project on the boil will see a second column stalk added and better control, more functionality from the the wipers, but it's no more at the moment still than an assortment of junk parts and an idea.

Been having a think about this, it's a subtle point what difference it could make, but worth adhering to the original design without good reason not to. Drew the little sketch below. Seems the idea for this offset in the linings might be to maximise the use of self-energising forces, and minimise the, counter to those, de-energising forces, and perhaps to equalise the wear across each shoe of the pair as much as possible, even if overall braking performance was reduced -and too much rear braking is quite as bad as too little, other than for the handbrake. It helps maybe to think of these forces at play as wedges, being pulled in and pushed out by the rotation of the drum.


This is not the time to ponder this and I'm more than usually wooly-headed this morning, but it's interesting all the same ... later.

thomas wrote:Continuing the winterisation theme, I've also been using rain-x products one for exterior and another type for interior glass

I used to use Rain-X on the outside of the windscreen on my daily driver, it was very good indeed as on a motorway trip, once above around 60mph, there was no need to use wipers as the rain would just bead up and slide over the roof. I didn't get on with the "anti-mist" product available at the time, and the "anti-icing" product isn't (or wasn't) one that can be applied and left, it's just a foam product that sits on the window overnight and prevents moisture and therefore there's nothing to freeze. Problem is that while it works, you do have to apply it before you think it's going to freeze, and then get rid of it the next morning if it doesn't, so it's no less work than having a plastic cover on the screen. The proper Rain-X outer glass product is quite old, I've got some copies of "Car Mechanics" from the sixties advertising it.

Unearthed some old Girling catalogues and found this diagram of 'our' rear brakes. Two features stand out: the little nicks on the edges of the shoes, absent from even genuine AC-Delco shoes; and that the shoes are lined pretty much along their full length. I expect with wider and stickier tyres than original specs, some cars could handle more rear braking, but the cardinal rule is that the front brakes should lock up long before the back ever could.

These are links to larger versions of the same images.





Dumped pic here of the Girling Supervac too, in the hope of identifying a replacement master cylinder which could bolt on to this - dual-circuit, aftermarket - and for which supply of replacement seals etc. would make it a good long-term fix for single-circuit inadequacies.



This is a link to a pdf document (4.3MB) of a few pages of information on servicing the Girling Supervac fitted to HB Vivas:

I'm sure the chap who exported my old Sportshatch to Australia has fitted a Subaru master cylinder, but I don't know what model it was from. I have an idea that he also had to block off one outlet to match the HC brake layout. Obviously being in Australia he has more trouble than we do in getting service parts.