Rear disc conversion

[twodoorgaz]

Hi folks.

This forum has always been an amazing source of knowledge for disc conversions with some fantastic home-engineered solutions (I have used the search function) and thought I'd check-in having finally bit the bullet and ordered a Heystee front disc brake kit... (I blame gin and credit cards) and I'm starting to plan the brake system on my (rather custom) SWB SIIA (of relevance here is that the axle internals are late SIII SWB Spec - 24 spline outers/two small wheel bearings).

I'm starting from a bare chassis so I have a nice clean canvas to work with. I'm hoping for some assistance in choosing parts for two different options: 1) front discs only 2) front and rear discs. In both cases I would like to keep the SIII Servo-assisted pedal box I have, rather than moving to a modern-looking Defender pedal box.

 

Front discs only

I suppose the basic approach would be to use an earlier Ninety master cylinder bolted onto the standard Series servo-pedal box and to retain the 10-inch rear drums.

Q1: Would there be an benefit in fitting the rear drums and backplates from the 'same' Ninety from which the chosen front discs/calipers and master cylinder are intended? And if so, I assume they would be a straight swap onto the series flanges. Here I suppose the nicety would be that the wheel cylinders would exactly match the front callipers and the master cylinder.

Q2: As the disc/drum LR Nineties (with the early Type-50 servo) used an 8" diameter servo, but the Series only used a 6" servo what would be the impact of using the smaller servo with the disc/drum master cylinder. Is it simply a case of the pedal action being firmer/more difficult with the smaller servo or would it actually impact brake performance. I would stump for one of Heystee's 8" Series-type servos if it makes for a better engineered solution, but they are quite expensive if it is just a luxury.

 

Front and Rear Discs

Q3: My understanding is that the Master-Cylinder needed to run rear discs needs to be the type fitted to the 300TDI-onwards Defenders with a different design of servo (11") and pedal box. Which would mean moving away from the Series pedal box using a modern pedal. I did buy one of these, but it won't look right in the vehicle - plus the servo's size means a tweak to the wings/bodywork which I don't want to do. Unless I'm wrong? This is the reason I am currently planning to use front discs only as I would like the install to be a bit stealth and would like to keep the Series pedal box/pedals.

Q4: If I did go for rear discs, is it necessary to pay Heystee another £500 for one of their rear kits (which consist of a calliper bracket and a hub) or could I simply use the remarkably-similar looking genuine calliper carrier and hub from a 300TDI defender (or even a disco)? I'm sure that Jon White wrote a post on this in the past (110 calliper brackets and I think RR hubs, but I'm struggling to find it).

 

Really appreciate any help here.

 

Edited May 5, 2018 by twodoorgaz

[secondjeremy]

What on earth are you going to use it for to warrant this braking performance?  What engine are you fitting?

[Bigj66]

I asked Heystee what master cylinder I should use with their front disc brakes and 8” servo and their reply was:

“You can use either the NRC9529 (Defender 90) or the NRC8690 (Defender 110). It is wise to mount an proportional valve between the master cylinder and the rear drums to balance the pressure between front and rear brakes.”

I suppose it depends on the performance of the engine you have - as already stated. I’ll go with front discs and rear drums with my 130hp engine. I know there are drum brake upgrades but the simplicity of disc brake maintenance sells it for me.

[twodoorgaz]

Thanks very much BigJ, thats really very helpful.

 

Re: the engine... its part of quite a big project

• I already have the parts needed to build an 050A-ratio stumpy R380 - including the ashcroft stumpy kit, 050A layshaft and the Ashcroft adaptors that I can retain the series transfer box. I just need the core donor TDR R380 to complete.
• I also have all the parts I need to build one of two engines (I haven't decided yet):
• Option 1: a 17H 2.5 block, dressed up as a series unit. Stage 2.1 head, balanced and Megasquirt. This is the current preference as, other than the TB it will look stock.
• Option 2: A red graded 38A V8 block (built-up as either 4.0 or 4.6) running carbs and megajolt (yes, I know... carbs are ridiculous). Plus a Milner adaptor kit.
• Suspension: Parabolics plus the front ARB from a Marshall ambulance.
• Steering: P38A steering conversion.
• Axle internals currently at 1981-spec, but rear to get 4-pin centre from Ashcroft and a pair of HD 24-spline shafts.

 

Again, I already have all the parts above, except the MS/MJ, the R380 core and the rear axle upgrade bits.

 

It isn't actually about braking performance. Its more a deep loathing of the set-up and maintenance of drum brakes. When they're good, they're very good (driven some SIIIs with incredible stopping power). When they're bad, they're rebuilt with the best quality parts we can find in the 21st century which tend to be clown-shoes - its a personal gripe, tainted by my last LR build in which I bought the best quality parts I could find, built-up a 1981- TLS system and still ended up with dodgy adjustors, oval drums and months of chasing adjustments. Discs work - consistently and with minimal fettling.

 

There is absolutely no need in the world to use rear discs on either of my setups - but for a few hundred quid, if its doable, I may as well include them while its in bits.

Edited May 6, 2018 by twodoorgaz

[xychix]

I'll likely be in the market for a defender 90 / 110 master cilinder as well (see my topic on binding rear breakes).

keep me/us posted on what you encounter of if the master is a straight fit (will the same copperpipes and their threading fit? can the old paddle be fitted without any issues? etc etc.) 

 

[Cornish Rattler]

On ‎5‎/‎5‎/‎2018 at 9:23 PM, twodoorgaz said:

Hi folks.

This forum has always been an amazing source of knowledge for disc conversions with some fantastic home-engineered solutions (I have used the search function) and thought I'd check-in having finally bit the bullet and ordered a Heystee front disc brake kit... (I blame gin and credit cards) and I'm starting to plan the brake system on my (rather custom) SWB SIIA (of relevance here is that the axle internals are late SIII SWB Spec - 24 spline outers/two small wheel bearings).

I'm starting from a bare chassis so I have a nice clean canvas to work with. I'm hoping for some assistance in choosing parts for two different options: 1) front discs only 2) front and rear discs. In both cases I would like to keep the SIII Servo-assisted pedal box I have, rather than moving to a modern-looking Defender pedal box.

 

Front discs only

I suppose the basic approach would be to use an earlier Ninety master cylinder bolted onto the standard Series servo-pedal box and to retain the 10-inch rear drums.

Q1: Would there be an benefit in fitting the rear drums and backplates from the 'same' Ninety from which the chosen front discs/calipers and master cylinder are intended? And if so, I assume they would be a straight swap onto the series flanges. Here I suppose the nicety would be that the wheel cylinders would exactly match the front callipers and the master cylinder.

Q2: As the disc/drum LR Nineties (with the early Type-50 servo) used an 8" diameter servo, but the Series only used a 6" servo what would be the impact of using the smaller servo with the disc/drum master cylinder. Is it simply a case of the pedal action being firmer/more difficult with the smaller servo or would it actually impact brake performance. I would stump for one of Heystee's 8" Series-type servos if it makes for a better engineered solution, but they are quite expensive if it is just a luxury.

 

Front and Rear Discs

Q3: My understanding is that the Master-Cylinder needed to run rear discs needs to be the type fitted to the 300TDI-onwards Defenders with a different design of servo (11") and pedal box. Which would mean moving away from the Series pedal box using a modern pedal. I did buy one of these, but it won't look right in the vehicle - plus the servo's size means a tweak to the wings/bodywork which I don't want to do. Unless I'm wrong? This is the reason I am currently planning to use front discs only as I would like the install to be a bit stealth and would like to keep the Series pedal box/pedals.

Q4: If I did go for rear discs, is it necessary to pay Heystee another £500 for one of their rear kits (which consist of a calliper bracket and a hub) or could I simply use the remarkably-similar looking genuine calliper carrier and hub from a 300TDI defender (or even a disco)? I'm sure that Jon White wrote a post on this in the past (110 calliper brackets and I think RR hubs, but I'm struggling to find it).

 

Really appreciate any help here.

 

I'm doing the same thing once the restoration is finished 1970 2a swb 200tdi, atm I've done a ground up rebuild with re-built axles inc std 10" brakes, don't wan't to go the 11" front brake upgrade as I've used them before on another project and was never happy with them so on this one I will run it on the std brakes and as soon as I get everything in from Heystee and paddocks I will do the brake conversion in the winter months as I have a log burner in my garage to keep me warm 

[Jon White]

You’ll find that the series 3 servo will work to a degree, but I found it didn’t offer enough servo assistance, so updated to an early 110 unit which is much improved. The series 3 and defender master cylinder is interchangeable the only difference is the brake bias. The series has a 50:50 split where the defender on puts more bias up front. I’m still running the series master.

i did indeed post how to bolt on rears using landrover parts many moons ago.

im using, early 90 drum braked rear stubs, with Range Rover disks hubs and Calipers. I used the Caliper brackets from a disk braked Salisbury rear from a 110 which bolt on after thinning them down by a couple of mm to get the disks correctly aligned (can’t remember the measurement sorry, but it’s easy enough to fly cut a bit off of them on a milling machine). Use 24spline shafts, early “thick” defender drive flanges and it all bolts up.

there is little difference in braking performance compared to well adjusted and maintained drums, however for me it’s the need for minimal maintenance that sold me. We have very sandy soil in my area, and I got fed up of the need to pump the brakes three times before they worked after a play day, when I had drums.

hth

jon 

Edited May 7, 2018 by Jon White

[Cornish Rattler]

Yeah its the easy maintenance that does it for me too

[Snagger]

I did the rear disc conversion to a 110 Salisbury axle, and then installed that with a Discovery front axle to my 109.  The entire brake system was lifted from the front axle donor, save for the pipes, hoses, and critically for you, the pedal box.  

I used the smaller diameter Discovery servo, which has similar dimensions to the SIII, but I needed to make an adaptor plate to allow for the extra length of the later unit's operating rod to the pedal.  That, in turn, required a small amount of fettling of the wing top for clearance, but if I recall correctly, that was just folding the edge return to be bent to an acute angle at that spot, no cutting.  I used the donor's biasing valve in the rear brake line, though 110s don't have this, as from an insurance perspective it was easier to say the entire brake system had been transplanted with no changes to balancing or efficiencies.  To be honest, the disc brakes are dead simple to maintain and do give beater feel, so are easier to use heavily without locking up, but maximum braking is limited by tyre grip on a Series vehicle, not by the brakes themselves (if correctly maintained), so it is quite a lot of work and expense for little benefit unless you're already fitting coiler axles (which has other benefits too, like far greater steering lock which will reduce your turning circle by about 30%, I estimate).  

I also did the P38 steering conversion, which is simply fantastic, especially with the increased lock from the Discovery axle.

As for the engine, I'd consider a highly tuned 2.25 with all the ACR bits if you're getting close to IVA territory just to have historic status to save on road tax and some city charges, but if you have enough points elsewhere that it doesn't matter, then I'd go for their 2.5 with all the bells and whistles that I could afford, as it'll be an easy fit and won't have the cooling issues or hydrophobia that V8s suffer.  Sure, it's not as smooth or musical, but it'd have plenty of poke for little installation effort.

The brake and steering work are on my blog if you want some ideas how I did it.  Clicky sig below.

[Gremlin]

Rear discs via lr parts on a series salisbury for reference................

 

Been away too long from here...................

 

Grem