Disc brake setup for an 88

[ejparrott]

I'm starting to find it more difficult to get under the 88 and adjust the brakes every month, well not so much get under but get back up again afterwards. I'm almost on the point of converting her to disc so that the maintenance is much easier, and therefore more likely to be done and done properly.

I'll state now, that peoples opinions of me for converting her to disc are not welcome, and I know full well that properly setup drums will stop her just as well.

I've been going through the parts catalogues again, having previously sorted out a system for The 109, which I've not yet implemented as her brakes are working well and have not yet required adjustment as she does about 30 miles a month tops. I'm keen to avoid the mega expensive G-valve thingy, partly to keep costs down, but also because, according to the parts catalogue, there isn't a requirement for it, it being dropped on later vehicles.

So, has anyone done such a thing, retaining the 10" SLS rear drums? I've an idea in my head that there's a problem with rear wheel lockup but can't for the life of me remember all the circumstances.

I have a pair of 90 front callipers in stock that need a full rebuild which I can do ( clean, paint, new seals, stainless pistons etc.) and I do also have a pair of disco rear callipers in the same state. Rebuilding callipers doesn't worry me, nor does the assembly of the component parts and the modification of the hubs to mount the discs. If I can't have a disc/drum setup without the G-valve doobery, then I can always convert the rear axle to disc too, and I believe that this setup will work, studying the various parts cat pages. Your thoughts please?

[Nigelw]

I'd say go for it, but what parts catalogues are you looking at?

I was looking at the disc brake set up from Haystee automotive here in the Netherlands, granted, it's pricey, but top notch gear designed and built for series axles.

[Team Idris]

There are second-hand LDV/Ford transit load compensating valves on ebay if it works out too feisty on the back end.

[Jon White]

Yes, I ran disks up front, and stock (late) rear drums for a while with no valve without any problems.

Jon

[ejparrott]

Thanks Jon. I might just try it. She's a 1983 registered 1982 model, so late brakes. I don't use the brakes much, my driving style is to slow down much sooner and drop down the gears in any case, the rears never seem to wear or need adjustment, they just get a going over every other year or so.

Nige I've got the early 110 cat, the general 90/110/130/defender cat, and the disco cat. Cross referenced most of the parts, which are interchangable across some models.

Thanks Idris, will keep an eye on such items just in case!

[robertspark]

It depends upon the calipers as to whether you need a g-valve (or proportional brake valve).

Basically if you put the same size calipers all round, and when you hit the brakes at speed, what would happen is the weight of the vehicle would be pushed onto the front axle, and the rear axle would be under light load, so the rear would have a tendancy to lock up (not sure if you know what the g-valve does, but it basically has a ball / pin in it and its mounted at a specific angle so that when you hit the brakes hard, the ball is flung forward and blocks the port off to the rear brake lines, hence reducing the braking force to the rear calipers or discs.

Think of it as a surface area issue, hence large brake pads have great stopping power, but they can have the tendancy to lock up the discs (or drums) if they are larger than required. The calipers are therefore normally 'tuned' to the specific vehicle, more so on the rear than the front.

If you compare a 90 and a 110, you'll find that the front calipers / pads are similar (or the same ... sorry no catalogue to hand), but the 90 rears are smaller than the 110 rears, because of the 90 having less load on the rear under heavy braking (hence they would lock up / have the chance to lock up under heave braking if you had 110 calipers on the rear of a 90)

Couple of discussions here (second link may be better with manual pages):

http://forums.lr4x4.com/index.php?showtopic=57708

http://forum.lro.com/viewtopic.php?f=18&t=74595

The clever braking way to go is ABS, hence the electronics reduce the rear brake pressure under heavy braking automatically [there is a bit of an article here, from the litigation capital of the world] http://www.hotrod.com/techarticles/hrdp_1108_abs_for_hot_rods/

usual disclaimers apply regarding brakes, insurance, competence etc (i advocate nothing, only provide information [don't shoot messenger please]

[ejparrott]

(not sure if you know what the g-valve does, but it basically has a ball / pin in it and its mounted at a specific angle so that when you hit the brakes hard, the ball is flung forward and blocks the port off to the rear brake lines, hence reducing the braking force to the rear calipers or discs.

I didn't, now I do, thanks for that! Whilest I do understand the major points, like matched callipers side to side and important of quality parts, maintanence scheldules, the finer points such as the workings of a G valve or the PDWA, I have only a sketchy knowledge of.

Will have a read of the links you provided.

[robertspark]

For a comprehensive response, I should also mention that you could use a brake bias adjuster valve :https://www.google.co.uk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=brake+bias+adjuster&tbm=shop

It is basically a needle valve that you can manually adjust to set the bias (limit the pressure to the rear calipers / discs). It can be set by high speed braking and adjusting the valve to the point where the rears do not lock up under a number of braking runs.

Although I advocate nothing but education to make an informed decision, personal opinion is that it's not a very clever arrangement, given the following:

As it's a manual set valve, if also affects the braking to the rear under light braking too (in my opinion), because the needle valve restricts the flow in all braking applications.

Again in my opinion (not a braking expert, just a backyard mechanic), what you want is a braking system that operates at the near point of lockup and can self adjust to maximise that braking efficiency, hence it makes no difference what the caliper (pad) size is, what discs are installed or pad material, or surface if you are in an emergency braking situation you want something that operates at near lockup to stop as quick as possible --> hence ABS. Yes there are expert drivers who can reportedly out brake an abs system (not sure if that would the same on all surfaces though), and ABS can perform worse on snow, but little will work well on ice.

In order of personal preference for effective systems to prevent rear lockup I would have said:

ABS

g valve

brake bias valve (manual)

.... no valve .... (edit: or reducing the size of the rear pads / shoes to the point where they don't lock up!)

The g valve is a good device as it will provide the maximum braking possible up to the point when the rears will lock up, at which point the ball / pin is flung forward and limits the pressure to the rear calipers or discs (my 90 has calipers and a g-valve), the only negative is that (I think) its set up for a specific surface (g force to fling the ball forward) and vehicle weight i.e if you had weight in the rear the rear the rear axle would be less likely to lock up.... but I guess the valve is inclined too so if t doesn't reach it's tipping point, it probably won't be enabled regardless of the g-force under braking. (note the ball / pin also has a specific load (light weight) spring on it to "preload" the pin).

However trying to set one up on a vehicle it may not have been designed for (an 88) that may weigh less than a vehicle that had one (a 90) not sure how much margin there may be on the angle or what the weight difference is.... maybe looking towards a 90 for ideas on calipers, pad sizes, and g-valves would be a good starting point to make an informed decision should anyone want to change to discs given they are "similar" / close in many ways.

Maybe someone will come along and explain if there is a science to the valve angle or whether its tested in application specific (always learning).

[ejparrott]

Hi Robert, that's a very detailed and well thought out response, thank you. I'm familiar with needle valves, and I agree totally with your thought's on its effect on light braking as well as heavy. Further, I concur with your opinion of wanting braking force just before lock-up. This is the exact same I'm usually looking for...which is maximum adhesion from a steam engine, which happens to be just on the point of wheel slip, so exactly the same senario!

I think I'll try it without and with rear drums to start with as Jon did, see what happens. It's the starting point I think. As much as I think ABS would be great, I feel there's a lot of things to be added to it, like the sensors, the ECBM...and that can't even be programmed to suit a particular vehicle according to the hotrod article.

It all hangs on whether the insurance company will cover me anyway!

[Team Idris]

Insurance is tricky. Because even if it is okay now, time changes it toward standard. Our Fiesta went to France and failed the MOT on rear tyres. Although they were okay in the UK as a tyre 'type' fitted to the Fiesta's, they weren't the one for that model.

I've got a 4x4 S1 in the garage built as a 4x2. But landrover didn't record this fact. The generic heritage sheet says 4x4. So if I changed it back to standard I would need to log it as a mod It's definitely moving away from a time when you can change stuff

Maybe what you really need is a way of fitting auto adjusters in the brakes? That would be a neat mod that a few of us would copy It's only a 'thing' that ratchets up if there is more than a set amount of slack?

[Daan]

I reckon the heystee kit , using defender kit is the best solution; I suppose you could copy that. The 845 Euro may be hard to swallow, but looking at it from a manufacturer perspective, I don't think he is making a lot on that either. From a legal perspective, there is also some come back on it which you wont have if you start welding plates to your existing knuckle.

[robertspark]

There is also Zeus engineering too: http://www.zeus.uk.com/

Zeus Engineering

Unit J2 Dunkeswell Airfield, Honiton, Devon, EX14 4LE

Email - info@zeus.uk.com

Tel - 01297 300010

Fax - 01404 891803

[ejparrott]

I'm not sure Zeus are actually currently marketing them are they? That website's been like that for ages. I've forgotten the original maker, think it was Rocky Mountain, but the setup I'm looking at is the same as Gremlin used on his 109, a bolt on calliper bracket.

[Snagger]

Not all of this applicable as I used colier axles, making the front swivels different from what you're working with, and went to discs all round:

I have a complete Discovery 1 brake system except for the TD5 Defender master cylinder and the same front discs on the rear axle due to the depth offset from rotor to calliper (drum braked axle converted to disc, which would work as an exact copy onto a 109 rear axle as it has the same hubs and stub axles as the 110 version). The Discovery master cylinder appeared externally identical to the Defender version used except for the shape of the reservoir, being made to sit on an incline while the Defender unit is horizontal. I made an assumption that the pressures generated are similar given the matching external dimensions.

I used the bias valve in the rear brake line even though the rear callipers and pads are so much smaller than the front for two reasons - first, that it would be simpler to disarm insurers and inspectors by transferring a complete Discovery system without alteration, and second, that the max gross weight of a 109 and D1 is only 10kg different and a 109 probably has a lighter rear end (especially since I rarely tow), so would be more likely to lock up in slippery conditions.

In practice, the braking is very effective and roller tests on completion of the work and at subsequent MoTs have given excellent results. The braking is front biased, and that is evidenced by the difference in brake dust, but that is normal on most vehicles.

How much the bias valve is needed I suspect varies with wheel base as much as with weight. 90s, RRCs and D1s have them, but not 110s, even though the 110 has much bigger front brakes and a lighter (at east when empty) back end than the 100" models. I don't know enough to start guessing, but with such a similar MGVW and with the callipers and pads being D1 spec, the safest option seemed to be to retain the valve. I may be losing some braking performance, but not much, and I'd rather that than risk spinning out.

For a system using rear drums, then you need the older master cylinder. The SIII mcs produce large volumes and low pressures. The late models use high pressure and low volume. The disc/drum combination will need high pressure to the front but lower pressure to the rear. I think you need a 90/110 or 200 Tdi master to get the best results.

[ejparrott]

Thanks Nick

My friends hybrid with rangy axles has been running disc all round for many years now, he's still got the series pedal box servo and master on his, but it's a different one to mine. It might be that I need to go to disc all round as he has, or I might need to change my master. Will dig out the parts cats again!

[Snagger]

I initially used the 109's master cylinder, but while it passed a brake test at the MoT station, braking was awful. In fact, I d consider it dangerous. It was completely transformed with the Discovery servo and Defender MC.

The 109 servo and MC were transferred to the Lightweight when its MC started leaking. Both were dual line with the same servos, but the MCs were slightly different for the 10" vs 11" brakes. The threads ont he ports and the shape of the reservoir made it quite obvious they were different cylinders. With the 109 servo and cylinder (a stud sheared off the Lightweight's servo when I tried to remove the MC), the pedal became very heavy. Whether a fault occured in the 109 servo during transfer or whether it was down to incompatibility between the 109 MC and the 10" rear and 11" SLS slaves I don't know, but the braking was made much more difficult. I really do think it is folly not to use the matched MC on a brake system.

Regarding the rear brakes, a disc conversion is not difficult on a Salisbury axle, and I suspect a Rover axle would be similarly simple to alter. It's the front that gives the difficulty because of the swivel housings. Gremlin's conversion was an excellent example of low cost ingenuity.

[ejparrott]

Absolutly, and since starting to seriously read up on it, various in Auz have gone the same route as Gremlin, and there was one manufacturer working on the same basis but I forget now which it was, I think it was RM. The system I'm looking at is the same. I have a set of calliper brackets for a rear axle, and I see no reason why they won't fit a rover axle as well as a Salisbury, afterall, stub axles have the same bolt pattern do they not?

In what way was your 109's braking 'awful'?

[Snagger]

It was as if the pads had been greased - huge amounts of pedal pressure produced minimal braking effect and braking distances were huge. Just as well I was only taking it on a low speed test to the MoT station for an inspection on the work done.

I don't know if the bolt pattern for the Rover and Salisbury stubs is the same - the stubs themselves certainly aren't.

[ejparrott]

Ah, see what you mean. I've not noticed it that much on my friends hybrid, but I don't drive it very often. I'm up there next weekend, so I might borrow it for a trip out and see what it feels like, pretty sure it stops well though.

I have a spare front casing but not back, could try the bracket on that I suppose

[mad_pete]

To stop you have to turn the movment into heat. The best thing for this is the brakes the pads/disks heat up and stop you. If you lock up the wheel the brakes aren't moving instead the friction of the tyre and the road slows you which isn't as good. Abs keeps the brakes more in play by releasing and re-applying the brakes on lock up. But that's not as good as continuous braking just before lock up. Abs is largely about still being able to steer. Hence a good driver should be able to out brake abs. In snow you actually want lock up to create a pile of snow in front of the wheels. I am open open to the idea any of this May not be true.

[robertspark]

I did a rear drum conversion to calipers on my 90 using the well known sailsbury caliper brackets, but I have a 90 v8 with a HD (4-pin) diff so not sure if the axle flanges are different from any of the other rover variants. Needed to change the stubs to match the disc hubs as the inner bearing shoulder is in the wrong place with the drum stubs.

[missingsid]

I've just finnished building my series axles with RRC swivles and hubs etc. The rear disc caliper brackets will fit a series axle but you will have to play with the spacing of the caliper to disc. I used a spacer between the stub axle and axle case and front discs but others have spaced the caliiper bracket?

On the front I created a 23mm adapter for the RRC balls to series axle case.

Over the weekend I saw a Stage 1 V8 with Zeus front brakes and to be honnest wish I could have found them instead?

But then again I have disc front and rear axles with Land Rover parts for £700 so can't complain.

[ejparrott]

It is Zeus I was thinking of....

http://www.yican.com.au/DBrakes/DBrakes.html

I came up with this same idea about 5 years ago when my brother wanted disc on his 109. In the end he converted rangy axles to leaves and used standard rangy gear, but I continued to think about and reasoned that a plate bolted to the front of the hub could be made to hold the calliper...but I bottled it at that point fearing lack of insurance cover in the case of an accident. 2 years later I came across a company via a web search when I was first getting The 109 back on the road and was having no end of trouble bleeding the brakes. Then I thought if it's good enough a principle for them to market world wide then the method must be ok, so I built a frame to support a spare series swivel assembly ready to start making my own. Time rather got on a bit, and now I've found someone making them it rather makes it a waste of my time to do the design work yet again. He's offered me what I think is a nice price, and I already have a set of 90 callipers that just need a rebuild, so provided my insurers are happy I'll go for it.

[Bowie69]

Some stuff here about discs and series: http://www.expeditionlandrover.info/discBrake.htm

Just in case it hadn't been seen

[Gremlin]

Just to add my 2c worth, i run 90 calipers on my 109 with a late 200tdi 110 master, no valve thingy anywhere. Stops fine with no funny handling.

As to insurance problems i do understand your concerns, over here none of that is present. Hence i have been very reluctant to hand over any detailed stuff from my conversion, but my post is usally easy enough to see and copy.

I also was going to get a batch of brackets made to sell, but i quickly scrapped the idea due to liability issues! which is a pity but anyway...............