Brakethrough
THERE are a few jobs on old Land Rovers which take far longer than they have any right to do, and one of these is overhauling the drum brakes fitted to a huge number of Solihull’s finest between 1948 and 1993 when the Defender finally went over to disc brakes on the rear axle. Excluding the (now almost extinct) rear brakes fitted to long wheelbase Series Is and very early Series IIS there are three basic designs: 10 inch single leading shoe (SLS), 11 inch SLS and 11 inch twin leading shoe (TLS), the latter available in two widths. All have design quirks which can make working on them a frustrating experience, even if you are familiar with them. For the DIY novice there are very many ways to assemble Land Rover drum brakes incorrectly and I think I have seen most of them over the years.
The least problematic of the three types is the 11 inch SLS, found on the rear axle of most long wheelbase Series, Ninety/one Ten and Defender vehicles from 1959 to 1993. It is an utterly straightforward design with the shoes located in slots to allow vertical movement, one snail cam adjuster per shoe, and return springs top and bottom which, when fitted correctly (between the shoes and the backplate) pull the shoes against the backplate and keep them square to the drum. Like all these brakes they need a dab of copper grease on the moving surfaces to allow them to seat and adjust correctly, but the most common problem is people mixing up the leading and trailing shoes. They look identical but are not – the distance between the top spring hole and adjuster post is greater on the leading shoes than the trailing ones. Fit them the wrong way round and you will find that the adjusters on the trailing shoes just spin freely without contacting the posts on the shoes.
Eleven inch TLS brakes (front axle of all 107 and 109 inch Series vehicles, and 88 inch from 1980 onwards) present a couple more challenges. Again we have shoes that sit in slots with one adjuster per shoe: a single strong return spring runs from each shoe to a post on the backplate. The shoes do not bear directly on the backplate, but rest against threaded adjustable steady posts. That is the first problem. The steady posts have hard plastic heads which fall off, with the result that the shoes do not meet the drums squarely, giving inconsistent braking from side to side. The posts can be replaced with UNF threaded set screws and locking nuts, but are usually rusted solidly in place and take some shifting. Adjusting the posts is usually done by backing them right off, then getting an assistant to apply the brakes slowly while you rotate the drum to centralise the shoes. With the brakes hard on, the posts are screwed in until they contact the shoes and then locked with the nuts.
That may sound complicated, but it is nothing compared to the pain and grief which awaits you if you disturb the hydraulics and have to bleed air out of the system. To start with the bleed nipple is on the bottom cylinder, tucked away behind the swivel pin and hard to reach. If I am carrying out a major overhaul on this type of brake I normally replumb it so that the bleed nipple is on the top cylinder which makes access easier but does not solve the main problem, which is that the design of the wheel cylinders tends to trap air behind the pistons. There really is only one way to bleed these brakes, which is to remove the shoes and wind the pistons right back into the cylinders with G clamps so that there is no space for air bubbles to hide. Otherwise you can bleed these brakes all day with pressure bleeders, vacuum bleeders, £1000 professional garage bleeders, even turn the vehicle on its roof and bleed the brakes upside down, and the pedal will still go to the floor. The good news is that once the brakes have been bled and adjusted they work very well. So we come to my personal nemesis, the 10 inch SLS brake, found on the front axle of all short wheelbase Series vehicles 1948-80, and the rear axle of all short wheelbase Series vehicles, Nineties and all bar the last few 200Tdi-engined Defender 90s. That is quite a remarkable history and I cannot think of any other brake which remained in production unchanged for so long. The design is elegantly simple, robust and (when properly set up) highly effective. It does however have a few peculiarities resulting from its deeply ancient origins. You have to remember that in 1948, when the first Series I rolled out of Solihull with 10 inch SLS brakes all around, wheel-mounted hydraulic brakes were still a fairly new technology. Many new cars still had rod or cable operated mechanical brakes, or the hydro mechanical type with a single hydraulic cylinder in the middle of each axle operating the brakes on the wheels via rods and cranks. It took a little while before the optimal brake design emerged, and in developing the braking system for the new Land Rover, Girling completely failed to make provision for any vertical movement on the shoes. They pivot on a fixed round post at the bottom of the backplate, into which they locate via semi-circular cutouts in the ends of the shoes. With no adjustment possible on the post position, the location of the cutouts is absolutely critical, and this is where the problems begin. I strongly suspect that all the major brake suppliers are working from the same set of drawings, because almost every set of shoes I have bought over the last few years has had the same dimensional problem. I have written about this before: with the brake shoes in place there can be a gap of anything up to a millimetre between the drum and the bottom end of the shoes, even when the top end is so hard up against the drum that it will not turn. By laboriously sanding and re-profiling the top end it is possible to persuade the drum to turn, but you end up with a contact patch between shoes and drum that is maybe an inch long at most. The vast majority of the shoe surface is not in contact with the drum. As the shoes wear the contact area gradually increases, but by the time the bottom end starts doing anything useful the top end is pretty much worn down to the backing metal. Some makes are better than others, but none are as good as I would like. I have pursued this problem with a couple of the major manufacturers but with no success. It is possible to cut and weld the bottom ends of the shoes to move the linings closer to the drums, but it is not something that I am at all comfortable with doing to customer vehicles for obvious reasons, and in any case it should not be necessary. When I heard that LOF Clutches, already well-known for their heavy duty Land Rover clutch kits, were planning to start making high quality 10 inch SLS shoes and drums which were claimed to fit properly I was keen to try out this new product. What I needed was a guinea pig. Enter a rather shabby but charming Series IIA hard top, last in the Norfolk Garage about four months ago for, among other things, new rear brake shoes and drums. The front shoes and drums were in good order so I had
swapped the front drums to the rear and fitted new drums to the front with less than satisfactory results. The vehicle was now back in the workshop with a brake pedal which pulsed rather like an anti-lock braking system when the brakes were applied. Clearly the new front drums were not entirely round, which is a problem I have had before. So I made a call to LOF Clutches and a big box of brake bits turned up the next day.
The drums and shoes certainly looked good, but would they work? There was only one way to find out. I fitted them to the front axle, adjusted them up and took the vehicle for a short drive. There was still a very faint vibration under light braking which felt as though it was coming from the back, but the vehicle pulled up nice and straight with acceptable pedal travel. All too often when I fit a new set of shoes the pedal will go half way to the floor due to the atrocious fit. The situation will improve as the brakes bed in, but I would much rather have them work straight out of the box. Fitting new shoes at both ends simultaneously is just asking for trouble. Back at the workshop I pulled off the front drums and saw just what I was hoping to see: evidence of shoe to drum contact along the entire length of the linings from top to bottom. Job done.
I still had one other task to carry out on the little Series IIA, which was to deal with a tendency for the rear brakes to bind when reversing. This is another of the quirks of the 10 inch SLS design. The trailing shoe is a floating design, with a very weak return spring being counterbalanced by a spring inside the wheel cylinder, and no adjuster. The idea is that the shoe bears very lightly at all times against the drum, keeping it clear of water and mud in off-road conditions. The only problem is that if the trailing shoe is incorrectly shaped, the top end of it will try to dig into the drum when reversing, causing the wheel to lock up. On removing the drum I could see the black mark on the trailing shoe where it had been rubbing against the drum, along with a rather small contact patch on the leading shoe. With some careful sanding I soon had a vehicle which would go backwards just as readily as forwards. Ideally I would have fitted new LOF shoes and drums all round, but the rear brakes on an 88 do far less work than the fronts, and the overall braking performance now is more than good enough.
I should state at this point that I have no connection whatsoever with LOF Clutches, other than as a satisfied customer. It is safe to say that I will be using their products in my workshop from now on. It is great to see a small supplier actually addressing the problem of poor quality components that plagues the world of older Land Rovers. Hopefully with vehicle values continuing to rise we will see a few more suppliers offering bits which actually fit properly and do the job they are supposed to do.