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Thread: County rear disk brake conversion, pics & p/n's

  1. #1
    rijidij's Avatar
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    County rear disk brake conversion, pics & p/n's

    There's been a few County rear disk conversions on the forum. The 'easiest' way to do it is simply swap the whole rear axle for a Defender disk rear axle, but in my case the rear axle in my County has had the full Maxi-Drive treatment, so just converting the existing axle is the obvious choice. There are also some advantages using some County parts which will be detailed below.
    Apart from the rear end conversion, it is highly recommended to replace the booster/master with a more suitable unit.
    Thanks to SteveG who recently went through the process and saved me a lot of time researching what parts to use, we tried to do a conversion using parts which are fairly easy to pick up second hand and also keep the conversion as simple as possible.

    These are the main parts used in this conversion. There will most likely be other options, but this is what we came up with.

    · Twin diaphragm booster/master from Discovery 1 (300Tdi) Part #ANR2046 or ANR2416.
    · Rear callipers from D1 with mounting bolts and brake pipes.
    · County rear stub axles (if new ones are needed) Part #FRC3132.
    · County front hubs Part #FRC6139 (Wider bearing spacing than Defender).
    · Rear disks from RRC, D1, Early Defender. Part #FTC1381.
    · Laser cut calliper brackets (custom).

    First, the booster/master. The reason we went for a D1 unit was because the push rod length is the same as the County if you remove the diamond shaped spacer from the D1 unit.


    Remove this spacer from the D1 booster.





    The stud patterns on the boosters are quite different, the County has 4 studs, the D1 has 2.


    You need to drill the two holes in the County pedal box to suit the D1 unit.


    The two new holes are in line with the sides of the pedal box, so you need to cut away a section at the sides to allow room for a spanner to fit the nuts.



    Once the booster is mounted you need to fit the brake pipes to the master cylinder. The rear pipe will fit straight in, but the front port on the County master has a bigger fitting than the D1. If you get the pipes with the rear D1 callipers, one of these can be used to replace the front pipe on the master cylinder to the firewall as the fittings are the correct size. The pipe will be a bit long, but can be bent to shape. I chose to cut the new pipe to length and took it to a brake specialist to have the end of the pipe flared. He actually did this for free as it only took a minute.





    Now for the rear end. Basically the drum units are stripped right back to the axle housing.






    We used D1 rear callipers as these are easy to find, there's lots of D1 wrecks advertised compared to Defenders. Make sure you get the mounting bolts with them as they are 12.9 high tensile fine thread bolts, not that you couldn't buy some, but it will save chasing them up and they wouldn't be that cheap. Also get the brake pipes with the callipers so you can use one on the master as explained above.


    The only custom made parts are the calliper mounting brackets which I had laser cut, also the dust shield. You could get the dust shields off a wreck, but I just had some cut as a set with the brackets.


    The reason I chose to custom make these is, Defender mounting brackets did not suit the offset of the D1 callipers and disks. I had a matching face plate laser cut at the same time so I can machine the brackets to suit the offset we need.


    It might seem excessive to get parts laser cut, but the custom brackets actually cost less than half the price of new Defender brackets, and I regularly get parts laser cut for my business, so it was no big deal to draw up the parts and get them cut..

    This is the genuine Defender type calliper bracket.



    If your County is pre '88 '87 ? you should be able to use your original stub axles.
    I had to replace the rear stub axles on my '88 County as the later Countys had different stubs on the rear with a different bearing spacing in the drum type hub.
    Early County hubs and stubs are a better option than Defender hubs and stubs as the Defender hubs have a very narrow bearing spacing which puts more load on the bearings.


    This is the new stub axle, dust shield and calliper brackets fitted up. The four bolts that connect the calliper bracket are new as the original bolts from the drum setup are too short. The new ones are 50mm long.


    Fit the new disks, hubs and callipers.
    The original brake pipes from the drum brakes can carefully be bent to match up with the new callipers.


    Fit axles, drive flanges, brake pads etc. Bleed the system. All done !!!!




    The difference in braking performance is quite significant.
    Once you do a rear disk conversion on a County, it's one of those things you say, why the hell didn't I do this years ago.........all this time, I could've had good brakes.


    There's probably a few bits and pieces I haven't mentioned here, but hopefully I've covered enough.

    Cheers, Murray
    '88 County Isuzu 4Bd1 Turbo Intercooled, '96 Defender 130 CC VNT
    '85 Isuzu 120 Trayback, '72 SIIA SWB Diesel Soft Top
    '56 SI Ute Cab


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    Good write up. Thanks.
    Perhaps you might think of selling bracket kits. I have been thinking of converting the 110. Then I have two drum axles on the rear of the 6x6 as well.
    Was the tubed axle a part of the maxidrive kit?

    Didiman

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    Quote Originally Posted by 123rover50 View Post
    Good write up. Thanks.
    Perhaps you might think of selling bracket kits.
    +1!!
    Hercules: 1986 110 Isuzu 3.9 (4BD1-T)
    Brutus: 1969 109 ExMil 2a FFT (loved and lost)

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    Another vote for a run of brackets! I'll even pay up front.

  5. #5
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    Hi
    ill buy three sets

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    Quote Originally Posted by 123rover50 View Post
    Good write up. Thanks.
    Perhaps you might think of selling bracket kits. I have been thinking of converting the 110. Then I have two drum axles on the rear of the 6x6 as well.
    Was the tubed axle a part of the maxidrive kit?

    Didiman
    You must have a good eye for detail Didiman. I wondered WTH you were talking about "tubed axle" until I had a decent look at the photos.

    For anyone who is sourcing D1 calipers to do a similar conversion, be aware that the early ones had a coarser thread on the bolts that mount the caliper to the bracket. Not the end of the world - just something to be aware of when sourcing parts or making brackets.
    I'm not sure exactly when the changeover happened, but the ones I got from a '92 model were coarse thread, and the '97 model were fine thread.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

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    Just some questions,

    About your comment that the closer bearing spacing puts more load on the bearings. I'm a bit confused, if the mass of the vehicle is unchanged where does the additional load come from?
    And.
    Could it be an artifact of the change in offset of the wheels, the wheels became more positive (inwards) in offset and therefore the bearings needed to be closer to the centre of the load?

    The disk brake Defender has a different part number for the halfshafts, I understood there was a difference in length. Did you have to change your halfshafts (even the Maxi ones).

    Is the track unchanged front to rear?

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    Quote Originally Posted by Lotz-A-Landies View Post
    Just some questions,

    About your comment that the closer bearing spacing puts more load on the bearings. I'm a bit confused, if the mass of the vehicle is unchanged where does the additional load come from?
    And.
    Could it be an artifact of the change in offset of the wheels, the wheels became more positive (inwards) in offset and therefore the bearings needed to be closer to the centre of the load?

    The disk brake Defender has a different part number for the halfshafts, I understood there was a difference in length. Did you have to change your halfshafts (even the Maxi ones).

    Is the track unchanged front to rear?
    The bearing load thing I liken to two people of equal strength fighting over a stick. If one person has their hands widely spaced on either end of the stick and the other (second person) has them close together - then the second person can't control rotation of the stick as they don't have the leverage.
    If both people are simply pulling the stick in opposite directions the hand spacing doesn't matter (like your static load comment).
    That probably doesn't make sense to anyone but me

    No change in halfshafts. The defender hubs are both narrower in the bearings spacing, and narrower from inner bearing to the drive flange face (hence the shorter shaft). The Defender drive flange may even be slightly thinner on the bolt flange which would also contribute to the shorter shafts.
    The wheel mounting face remains the same dimension from the inner bearing on both hubs so track is the same between both.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  9. #9
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    Thanks for that, and yes I understand the stick analogy.

    So what you're saying about halfshafts, is that on my early Defender I can't use the same procedure unless I want to also change my halfshafts?

    Diana

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    Quote Originally Posted by Lotz-A-Landies View Post
    Thanks for that, and yes I understand the stick analogy.

    So what you're saying about halfshafts, is that on my early Defender I can't use the same procedure unless I want to also change my halfshafts?

    Diana
    Would need to confirm 100%, but it should be easier for early Defender.

    Pretty sure D1 hubs are the same F&R AFAIR, and same as Defender disc hubs - so you could use either.
    Should just need to get Defender disc rear stubs, D1/Defender hubs and some discs (early defender rear and D1 might be the same but would need to check). Could possibly be some slight disc offset differences from what Murray posted above but that would be all.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

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