Disc brake conversion

[rdarnell]

Got a little work done on the mock up of the rear disc conversion. Used a piece of 1/4 inch plywood to make template. Drilled out the axle opening using a hole saw and then transferred the bolt pattern to the template using the bearing housing as a guide.


Used a nut to extend the bolts which kept the template locked into place. Then I used a couple transfer punches to mark caliper bolts.



Then I cut out the center with a 4-1/8 hole saw and trimmed and radiused on the belt sander. Next step is to build a pair out of 3/8 plate.

[rdarnell]

Got the rear brake caliper brackets cut out on a plasma CNC using 3/8 mild steel plate.




To get the caliper to be centered over the rotor and allow the pads to clear I needed to remove 1/8 inch where the bracket contacted the rear axle. I am using Land Cruiser wheels instead of the split rims that came with my Patrol.

[rdarnell]

I am using a 7" dual diaphragm brake booster that I purchased on Ebay for $65. It uses a 1969-80's corvette style master cylinder with a 1-1/8 inch bore. I have basically the same disc brake setup on My FJ55 using the stock Asian master cylinder with a 7/8 bore. Most people change over to the later FJ80 that came with 4 wheel disc brakes, that master cylinder is a 1 inch bore. My FJ55 could benefit from it but I prefer the look of the twin reservoir of the early correct Asian MC. For the Patrol I will be using an aluminum with plastic reservoir from a 2007 Impala with a 1 inch bore. I save the weight and of the cast iron MC since I have to space the booster and MC away from the firewall. This past weekend I got some metal cut up and test fitted and then welded them up. The end of the booster was too big to allow the use of one piece of metal and as the steering column rises it interferes with the booster so I had to find about the right spacing to not have to modify anything on the Patrol. I finished the weekend with it drying so I do not pics of it installed yet, also the MC should be in today so I should be able to get all my lines finished next weekend.

[Esteban]

Looks great. I was curious at the beginning with the combinaton of the power booster and the 1-1/8” MC. Yours is a double diaphragm booster so it probably makes sense.

I run a single diaphragm booster with a 1” MC, and a proportioning valve to the rear and the drum brakes.

Would love to test drive your setup once finished.

Congratulations!


Esteban

[rdarnell]

not really sure if I needed the dual diaphragm booster but since the diameter is smaller than my Land Cruiser booster I figured it would be similar. Looking at some of Faux40 numbers and thoughts on his post I figured I would start there as well. His chart showed my single diaphragm Land Cruiser booster being about equal to the 7 inch dual diaphragm booster. I still want to add a brace to support the extended weight of the booster and master cylinder. I have a Wilwood adjustable proportioning valve that will be installed on the rear circuit. Hopefully I will make time this weekend to finish making the steel lines now that I have the master cylinder.

[rdarnell]

my FJ55 may actually have a dual diaphragm booster on it, if so using a dual on the Patrol would definitely be better.

[rdarnell]

Finished up the brake booster a couple weeks ago but forgot to post final pics.

I made a bracket to support the extra weight and length of the master cylinder and booster. Basically it just bolts on after the master cylinder and drops down to the fuel bowl bracket.






I also mounted the Wilwood adjustable brake bias proportioning valve on this same bracket. I had to redo some lines after I noticed that the fittings were bubble flare and not inverted flare... guess they do not make a 10M inverted flare valve yet. I also found out shortly after that the front bowl is for the front brakes on GM master cylinders... my Land Cruiser is opposite. Reflaring that line while in the truck was a bit of a handful since I did not have a vice in there and this flaring tool really likes a vice! Fortunately the Nickel Copper line is easier to work with.






With all the line in the right order and proper fittings installed this is my finished product.





Up next I needed to address the linkage connecting the pedal to the booster. The booster has 3/8 fine thread rod coming out. I purchased a universal kit to get the long threaded hex bar. I made some measurements, some cuts, and some welds and then I was ready to install and make adjustments. Since the rod is now adjustable but fixed to the booster I had to install and remove several times to get the length just right. I also had some rubber stops in my drawer of miscellaneous rubber things that worked out perfectly for the pedal stops. I still need to make a bracket and add a brake light switch since there is no longer a pressure switch on the end of the master cylinder. I could probably install a T on the rears somewhere and use a pressure switch but I think I will just go with a modern style switch.

[Esteban]

Beautiful work! Very nice and detailed pictures.