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: Salo's Rear Disk Brake Conversion  ( 15424 )
Salo de Swardt

« : July 07, 2009, 03:28:09 PM »

Rear Full Floater Disk Conversion – 1975 FJ40

Thought this write-up might be of value to some guys out there that have though of going the same route.

The FJ40 I have is a 1975 model that came out with drums all round. The drums on the J4 series are well know for not being the best in the business, hence my initial plan to upgrade the front drums to disks and re-conning the rear.  After closer investigation I found that just about everything had to be replaced in the rear and a quick cost comparison showed that the difference in replacing everything compared to upgrading to disks would work out at about R2000 more. The total cost to date has been:

1)   HILUX Calipers = R1500
2)   Caliper recon Kits = R 150
3)   60/75 series front Hubs = Free from N1
4)   Hub Skim = R200
5)   New Disks   = R900
6)   Bracket Manufacture = R300
7)   New Pads = R 350
8)   New Brake lines = R 250
9)   Rear Brake plates = R 300
10)   Dust covers = R 160
11)   Wheel Bearings = R 720
12)   Rear bearing seals = R 160
13)    Inner shaft seals = R80
14)    Heat Resistant Paint = R150
15)    New extended studs = R276
16)    SS Washers = R42

Total = R5 538 – Way over budget. R1140 of which was the cost of the hub recon.

I obtained two 60/75 series front hubs from N1 4X4.  Had them cut by an engineering shop to create a disk with cutout section and caliper mounting points. The right hub front would go to the right rear and the same for the left front to the left rear.

The brackets would be bolted onto the back support of the rear axle.  The holes in the hub disk proved to be a perfect match with the axle back plate mount. 

A problem was experienced in this perfect marriage that a small ridge had to be cut off the edge of the bracket so it could fit over the ridge of the axle.

This provided me with a mounting point for the rear calipers. Picture taken to test alignment of holes. 

The build was done in 2 phases a measure and fit phase were the older pasts were used but the final build would be all new parts to ensure I had a base line for future modifications.

The one hub I received with the 40 turned out to have oval stud holes.  The previous owner addressed this problem by welding the studs onto the back plate of the hub.  When removing the studs to fit the disk to the rear of the hub the old welding points did not create a smooth surface.  I decided to skim the rear of the hub.  This turned out to be my 1st mistake.  I had 2mm skimmed of the back of the hub.  This is not advised.  If you have to skim remove as little as possible.  To rectify the oval stud hole problem I had an engineering shop drill new holes in the hub.  See picture further down.

The hubs were wire-wheeled and painted 3 layers of Hammerrite paint.  New bearings were installed into the hubs with new rear grease seals.

What I found too was that the OEM J4 rear studs were shorter that the OEM 60 front studs.  This is because the longer stud needs to take the disk into account.  12 new 60/75 series studs were purchased.  This turned out to be too long. Necessitating a spacer to pull the stub back slightly.  The reason being that the cone of the wheel nuts were touching the shaft of the stud. The picture shows a single 2mm washer, a 2nd one was added later.

The next step was the assemble everything.  First was the back plate and permanent fixture of the bracket.  I used 6x #7. OEM front hub back plate bolts to secure the bracket. A number of items are secured by these bolts. 

The order was as follows:
1)   Bracket
2)   Axle
3)   Paper gasket
4)   60/75 series front disk backing plate
5)   Paper gasket
6)   Dust cover.

I found with trial and error that the 60/75 series brake calipers were smaller than the HILUX calipers.  This necessitated a small modification to the back plate by removing the “ears” at the top and bottom of the caliper bracket.

The hub came on next! The following pictures were taken during my assembly trial runs to ensure the disk would center on the caliper.  This proved to be more difficult than thought. The hub was secured and measurements made. A feeler gauge was used to determine the exact amount of movement required. Measurements were made on both sides of the disk and the difference and direction of movement required calculated.  The disk was 1.8mm to far to the outside!  Almost the exact amount I had skimmed off the back of the hub :(

This could be rectified by one of two ways. Option A was to remove 1.8mm of the mounting side of the bracket. Or by skimming the calipers with 1.8mm.  I opted for 1.8mm off the calipers. 

The end result was a perfect fit.

I have not tested the braking capabilities yet but with 4x oversized HILUX calipers, new master cylinder and booster it can only be much better that 2 drums on a 33 year old master cylinder :)

The calipers were re-conditioned before assembly too.   New sleeve kits and rubbers installed.  Spayed with HIGH heat resistant paint used for manufolds and exhausts.

Keith Richardson
All Bezels
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40's Rule

« #1 : July 07, 2009, 04:16:37 PM »

As it is my 40 locks up the back wheels far too easily - I would hate to see what it would be like with rear disks - Eish

But - nice job and WAY over budget  :-\ :-\

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Salo de Swardt

« #2 : July 09, 2009, 10:46:03 AM »

I thought of installing a LPS between the front and the back wheels but decided to have a look at the real world 1st.

All my cylinders were shot and had to be replaced. Drums at max and needed skimming, had to use front.

Estamated cost with new shoes was about R2000 cheaper but desided for 2k its worth it.  ;D

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