Tech article by TOFIC

Some of you have asked about the rear disc brakes for your Bronco's. Below is a summation of about 5 years worth of research and experimentation with 2 totally different rear disc brake systems, both of the original FORD equipment on their respective vehicles. This is no way comprehensive and is my opinion and experiences and should be treated as such. Most, if not all, the facts can be checked if you wish to follow up on this.

I have used two different rear disc systems on my 2 Broncos.

One system came from a 1973 Ford Thunderbird car. This was the “Big Bird”. As I recall the car was a sick green and had four doors and was a real boat. My shock came when I found rear discs on this car. Digging discovered that the brakes were available on this car at this time. The option only lasted for about 5 years so if you find one with it on it. GRAB IT!! If you don't want it let me know I will buy it. For obvious reasons, I call this the Bird conversion or something similar. It was on a 9” rear end with the small bearings and the small bolt pattern. Keep this in mind when you are hunting for rear discs as it is critical.

The other system came from a 78 Lincoln Mark Car. Again, a real boat, white in color and had all the options, (except hydroboost which was strange). Big four door SOB and just about bent my Jackall getting the thing up into the air. Some Lincolns had rear discs, and if you get a chance to get this setup go for it. You will NOT find this in a U-Pull yard. These are long gone from these cars before the wreck even hits the yard. The hot rodders have this market sewn up and the yard guys are in their pockets. You will find this setup on cars out in the boonies; behind the barn type discoveries so to speak. I found mine this way. Bought the car for 100 bucks and made money by the bucket load on the car. That is another story. This is the desirable system as it has big calipers and rotors. This is also a 9” rear-end with the big bearings and large bolt pattern. I call this system the Mark conversion or something similar.

Now to the basics. On both systems, when you are stripping the brake systems out, take everything. All the little clips, hoses, brackets, clamps, brake fittings, E-brake cables and lines that is attached to the system. Get the Master Cylinder and Proportioning valve or H-block depending what is on the car. If you forget or don't get one little item and go to buy it at the local parts store, you will learn what sticker shock is real quick. If it is attached connected or remotely part of the brake systems take it.

There are two different types of rear discs, one is called floating caliper and the other is called sliding caliper. Most of you are familiar with sliding as that is what most front discs are. Obviously it is because of the way the calipers function that the systems work. I have had both. The bird conversion was floating, the Mark conversion is sliding. If you want to see the two different systems get the Hayes manual for the Big Mercury cars in the 80 to 90 years and it is illustrated there. I have 2 of these manuals and they are very thoroughly explained in these manuals. If you are going to do rear discs get one of these manuals, the reference is worth the price.

The Bird conversion is usually floating, do not be afraid of this, it works very well. The discs are about 11” in diameter and are unidirectional. Grab the discs for a Bird conversion. If you have time and the energy get the front disc system, all of it. Even though the caliper mount may not work you will be glad you did get the rest if you get a brake imbalance condition in your Bronco. Simple exchange of the fronts fixes this very quickly. This system is easy to install and magnifies the rear braking power by many factors. It really shines on rock crawlers, mudders and people who like to swim with their Broncos. If it gets wet, the rear discs will save your ass more times than not. Decent size discs, easy to maintain and not expensive to buy.

The Mark conversion, this one is the big one. If you get monster meats on your rig or love to get into the deep and dirty stuff this is the one you want. The Mark conversion is always sliding caliper. I have never seen a floating caliper on a Lincoln. Not saying there isn't one, just I have not seen it. Again, as above, grab all the parts off the brake system. If you have time and energy get the front discs calipers and mounting hardware. If you have problems with your system you will be glad you did this. One exception with this one, unless the rotors are new or near new, don't bother with them. They are unidirectional and very expensive. This is to say that each rotor is labeled, one left one right. There are better replacements for this system. I have seen the Mark Conversion with 13” rotors!! This is serious stopping power. This system usually has hydroboost attached to it. If you get anything, get the hydroboost unit then get the discs. Most Mark conversions are on 9” rears big bearing big bolt pattern. Check the rear end, some Lincolns came with Detroits in them. Don't leave this behind!! Again, bolts on to a big bearing rear-end. The replacement rotor that usually works is a Jeep rotor off a CJ7 or something like that. I have a parts guy running down the details now but we both seem to agree the front discs off a 78 ½ ton 4x4 pickup should fit into the rear as the calipers are the same size. The pistons in the calipers are even the same size. More on this later as this is assumptions on our part and we are still looking into this.

I have run the Bird conversion on a 1968 Bronco and it worked well. 6 cylinder with manual brakes and the system had no problems locking up the 31 inch rubber on the truck. Bear in mind this is with the Birds MC and H-block not the Bronco's. great system worked well and gave me no grief.

I am presently putting the Mark conversion on my 73. This one has a 355 going into it and has 33” M&T's on it. I will keep you informed on this one. Have a major problem with mine, it was born with the small bearing rear-end and I have to decide whether to alter this rear to accept the brakes or get a new big bearing rear-end. As my present rear has a Detroit in it and works great I am leaning to altering it accept the discs. I have altered another Bronco to the Marks brakes, it was a 77. Worked great with the jeep rotors. Was a bolt on and he has had no problems with the setup. He loves taking it to Midas for a checkup and watching the 'technicians' go nuts trying to figure out where to get the new pads for the rear discs. After the pad episode they are really stuck when they cannot figure out the rotors. (The mark rotors are really different appearance wise than the Jeep rotors) He lets them run around for a while and then tells them to “forget it, I will change them tomorrow”

Why the Bird or Mark Conversion?? It is all FORD. No welding, No adapting, no screwing around. It either fits like a glove or it will not fit, no way. The rear disc e brake system works. Most conversions do not allow for this. These conversions the emergency brakes work period. I am lazy; I will not reinvent the wheel when someone else already has done it. If it is bolt on, it's for me. Get my drift?? It works all the way not just part way. These are the only way to get fully functional rear discs for your horse. Not that other kits are bad, just a lot of work, or incomplete, or both. Also parts are readily available and relatively inexpensive. Worst case is a FORD dealer but he is still cheaper than some of the aftermarket kits.

Get the FORD version and get it stopped quickly. These conversions are out there and cheap if you look right. GO FOR IT!!

Tech article by TOFIC (The Old Fart in Canada.)