MAKING A CLEAN BRAKE

Horton’s 924S’s parking brake – also designed to be an emergency brake, of course – had scraped through the MOT test, but plainly needed more than a straightforward adjustment. Yet what should have been an almost equally simple shoe change proved to be an

One of the issues that arose from the 924S’s last MOT test was the efficiency of the parking brake – or rather the marked lack of it. Some hasty adjustment achieved more or less the desired result, at least as far as the brake rollers were concerned, but it didn’t feel 100 per cent right. The lever inside the car wouldn’t seem to stay in the fully down position, with an annoying tendency to flag up the red warning light in the instrument panel, and although the wheels rotated reasonably freely by hand, out on the road I often had the distinct sensation that the shoes were occasionally dragging against the inside of the drums – with an obvious adverse effect on both the car’s performance and most likely its fuel ‘economy’.

I put off the evil day for as long as possible – I knew that I would have to disconnect the hydraulic lines to the two rear calipers in order to take them off to remove the discs – but eventually circumstances forced my hand. A trip down to Porsche-torque in Uxbridge for this month’s how-to story had seemed the ideal opportunity belatedly to show off the car to proprietor Sid Malik – he, too, has long been an enthusiastic proponent of these transaxle models – but even before the end of my own street there were some disturbingly heavy knocking sounds from under the rear, and at low speed it was clear that the brakes were dragging quite noticeably. Back to the trusty old VW Passat, then…

The following day, after an unlikely burst of enthusiasm for a dreary late-november morning, I got the rear of the 924S up in the air on my trolley jack. Wheels off, calipers off – with the flexible hoses clamped to minimise fluid loss, and the subsequent bleeding that would be required – and then the drums off. There was nothing immediately obviously wrong inside the first one, I decided, and plenty of friction material on the shoes – although unsurprisingly they did appear to have somewhat glazed surfaces; the drum, too, would need a good going-over with some emery cloth – and so it would probably be worth just dismantling, cleaning, lubricating (where appropriate) and reassembling. All it would cost me would be some time.

Yeah, right. Two hours later, still wrestling with the shoe-return springs inside the lefthand drum, and then the shoes’ arguably even more awkward anchoring springs (more on these in a moment), I was beginning to wish that I had ignored the binding brakes, and simply driven the protesting Porsche down the M40 for Sid to have a look at on his wheel-free lift in his warm and dry workshop. There is always a knack to these drums, I think, rather than a specific technique, and unfortunately (or perhaps fortunately) I now ‘do’ them so infrequently that I simply forget it from one occasion to the next. And crawling around on the floor doesn’t help.

In the end – and again you’ll see in a moment why I use that phrase – the method I evolved was to attach one shoe to the hub, with its lower end located against the actuator at the base of the light-alloy casting, and the transverse lower return spring hooked into it. This enabled me simultaneously to locate the free end of the lower spring in the opposite shoe – carefully pushing the central portion of the spring into position above the actuator with a screwdriver; it tends to want to sit below it – and then to ease that shoe into

place, securing it with its own anchoring spring. It requires some dexterity and determination to manouevre the second shoe so that it engages correctly on the actuator, as well as strong fingers, good eyesight and not least another judiciously placed screwdriver as a lever, but it’s not impossibly difficult. Just teeth-gnashingly awkward.

The next step, and with the second anchoring spring in position (yes, I’ll come back to those in a moment, I promise), is carefully to pull apart the tops of the shoes – not too much effort is required for that, fortunately; just make sure that you don’t ‘lose’ it all at the bottom – slide in the adjuster, and then fit the upper return spring. And the simplest way to do that, I have concluded, is to hook one end into one shoe, and then to pull the free end back towards you with a suitable hook; I used an angled pick. This enables you to locate the hooked end of the spring against the hole in the shoe, and then finally to push it fully into position with your screwdriver blade. Job done.

Except, of course, that it wasn’t. Starting the same procedure on the right-hand drum, I spotted immediately that one of the shoes was losing a section of its friction material; most likely it was this flapping about that had caused both the intermittent binding and clonking, and the overall lack of efficiency. As usual in these circumstances I turned to the Euro Car Parts website, where I found a set of Pagid shoes for a very reasonable £49.99 including VAT. My local branch – Aylesbury – had them in stock, too, and in the event for just £37.49, again including VAT. (Is it just me, or does anyone else find Euro’s pricing structure utterly baffling? Oh, and I note today from the invoice that the ‘list’ price of the shoes – presumably without VAT – is shown as £115.13. Say what?!)

Back at base, I had the right-hand pair of shoes installed speedily enough (I was going back to the left-hand drum once I’d sorted this side), but as soon as I tried to slide in the adjuster discovered the kind of problem that makes you question the parentage of those who produce this after-market stuff. Basically, the slot at each end of the adjuster was very slightly too thin to fit over the shoes’ backing plates – or, to put it another way, since the adjuster was obviously an original Porsche part, the backing plates were very slightly too thick. Seriously? You mean to tell me that I am going to have to file the bloody things? Did it not occur to any of you people to find a micrometer, a measuring caliper, or even just a good, old-fashioned ruler – and make sure that this hardware actually fits the application for which you claim it to be suitable?

And so filing is what I had to resort to – after understandably reluctantly taking all four of the shoes and springs off again, of course. OK, so it wasn’t the proverbial rocket science – far from it, in fact – but you would be surprised by how long, and how much effort, it seems to take to shave off the required fraction of a millimetre of cold steel. (And it is essential, I believe, that the ends of the shoes can both slide and rotate freely inside those adjuster slots. Any unnecessary friction within the mechanism, compounded by an eventual lack of lubrication, can lead to the shoes failing to release properly. Which, of course, is where we came in.)

What, then, of those shoe anchoring springs I was banging on about? I had started by trying to use long-nosed pliers simultaneously to push them into position through the shoes’ backing plates and then twist them so that the hook on the inner end engaged over the edge of the hole in the hub casting. But this means coming at the spring at a slight angle, from outside the line of the driving flange, and due to the size of the pliers is never going to work. What I needed was the no doubt special tool devised by Porsche that would allow me to attack the spring through the same hole in the driving flange via which, when everything is back together, you turn the adjuster. Fortunately, I have roughly 40 years’ worth of screwdrivers and other old and largely worn-out tools stashed away in a drawer, and it didn’t take too long to find one that would – give or take a bit – engage sufficiently tightly in the outer end of the spring to do the job. You can find a use for just about everything sooner or later.

And that – finally – was about it. I shall conclude, however, with what I hope will be a useful tip for dealing with those adjusters, such that you can quickly set the shoes at the optimum distance from the drums. On both sides of the car the adjusters are fitted with the toothed wheel toward the rearmost shoe. Since both have a conventional right-hand thread, it follows that you have to rotate them in opposite directions in order to achieve the same result. Thus the one on the right-hand side of the car (below) requires a downward movement on the end of your screwdriver blade to expand the adjuster, and so spread the shoes, and the one on the left for the end of the blade to be levered upward.

It is also a nuisance to have to keep looking in through the hole to locate the toothed wheels again, after you have checked how easily the drums rotate, so using typists’ correcting fluid (which to my surprise you can still buy), I painted on a couple of visible marks: one on the edge of the disc, the other on the water deflector. Every little helps! PW