Rear disc conversion
(using Mark VII calipers and Ranger axles)
1987-1993 |
Want to run rear discs, convert to 5-lug, and NOT have to run special offset wheels? Here is your answer! With
the information below, you will be able to run Mark VII rear brakes using stock length 5-lug axles from Rangers or a Motorsport axle/drum kit. If you still have questions about this after reading it, feel
free to send me an E-mail at derek@wcfords.com. |
Little background information: So far, the most popular method of converting to rear brakes is using SN95 parts. There is a
problem with this. Since SN95 axles are approximately 0.75" longer than Fox4 axles, special offset wheels are needed to match the front tires and/or so they dont rub the fenders. Other than being able
to run the same offset rims front and back, this procedure has a few other benefits:
- Larger brake pad surface area
- Vented rotors (Cobra brakes are vented; GT brakes are solid)
- And larger rotors (10.5" GT rotors Vs. 11.25" Mark VII rotors. However, smaller than 11.65" Cobra rear rotors.)
- Cheaper to convert and replace (Mark VII Vs. Cobra)
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The catch? Mark VII's use 1.25" longer axles than Fox4's. So why am I recommending using Mark VII parts?
Cause with a couple modifications to the stock Mark VII brackets, the calipers can be set inboard more to use stock length 5-lug axles. No other special parts or difficult fabrications required. This is done
by "flipping" the brackets and mounting the intermediate bracket on the opposite side of the caliper bracket. Here is a picture showing the thickness of the intermediate bracket. By mounting it on
the other side, an inboard movement of its thickness and the thickness of the caliper bracket is achieved (approximately the nesessary 1.25"). |
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Also, these are not the only steps needed to run a rear disc setup. This article assumes that you have already
done the necessary modifications to the proportioning valve and replacement of the master cylinder. If you want more information on these procedures, they are available in the tech section. |
**WARNING**
Due to the design of the parts, Fox4 Mustang rear housing, and my lack of a need for an E-brake, this DOES NOT
cover necessary steps to include a functioning E-brake. Though it is possible to set up the car with a functioning E-brake, I have only speculation. No hard evidence and/or experience. |
Parts that you will need (any year, '82-'90, Mark VII without ABS unless otherwise noted):
- Caliper bracket
- Intermediate bracket
(not sure if this is the technical term; its the bracket between the caliper bracket and the caliper)
- Calipers
- Brake lines
- Axles
(late 80's/early 90's DRIVER'S SIDE Ranger axles with 9" drum brakes or axles from a Motorsport M-1126-A
axle/drum kit)
- Brake fluid
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Special tools that you will need (other than a good assortment of sockets, screwdrivers, etc):
- Drill
- Drill bits
- Tube cutter
- Tube flaring tool
- Grinder
- Welder* (recommended, not necessary)
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Now that you have an idea of what is needed, here are the steps for the procedure. (Note: I did this conversion about 2
years ago with no intention on doing an article. All the information below is based on memory. Pictures of a step-by-step process are not available either. If/when I do the conversion on another person's
car, I hope to update this article.) |
This section covers the removal of the old brake drums and axles. There are no tricks here. If you have a hard time
following my instructions, a repair manual for removal instructions might be able to help. |
Parts removal:
- Secure the vehicle's front tires.
(Dont want the car to roll now.)
- Raise the back end.
- Set jack stands on the chassis.
(Not the axle housing since you need to get into the pumpkin.)
- Remove the rear tires
- Remove the drums
- Remove the diff cover.
- Remove the bolt that secures the carrier rod.
(The rod keeps the axles from moving inboard.)
- Remove the carrier rod.
- Push in the axles.
- Remove the "C" clips.
(these secure the axles so they dont fall off as your driving.)
- Remove the axles
- Remove the E-brake cables
- Undo the brake line
- Unbolt the backing plate.
(Its secured by 4 bolts/nuts onto the housing.)
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Thats it. At this point, you will have all the old parts removed from the car. The following steps first include
modifications necessary to the caliper bracket and intermediate bracket for proper caliper placement. After that, the instructions will be to reassemble the car. |
Bracket modifications: |
figure 2: 
figure 3: 
figure 4: 
figure 5:  |
- Use the right caliper bracket on the left side, and vice versa, without changing their relative position in relation to the car.
(this means, to use the bracket on the other side but dont flip or rotate them in any way. In a Mark VII, the caliper bracket has the bent edge towards the
center of the car. In our application, the bent edge will face away from the center. See figure 2)
- Cut the dust shield and the dust shield mounting "ears" off.
- Bolt the intermediate bracket on the inside part of the bracket.
(See figure 2)
- Grind the bracket edge and bolt head till it clears the rotor.
(Figure 3 shows why you need to grind the bracket and bolt.)
(You'll have to install the bracket, axle, and rotor to know exactly where/how much to cut. **RECOMMENDATION** Since the head of the caliper bracket to intermediate bracket bolts need to
be ground off, I suggest welding them to the bracket. If for some reason the bolts come loose, you wont be able to retighten them. Do not worry about permenently fixing these parts. You will still be
able to change brake pads. Figure 4 and 5 shows the bolt heads ground and welded.)
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Now that the necessary modifications have been done to the brackets, here are the installation instructions. (Assuming the
axles and caliper brackets were removed after a trial fit for grinding and welding.) |
Installation of the parts: |
figure 6: 
figure 7: 
figure 8: 
figure 9:  |
- Bolt the brake line bracket to the axle housing.
(See figures 6 and 7. Notice the bolt in the center? There is no hole
associated for this part and therefore must be drilled.)
- Cut and flare the brake line.
(See figures 6 and 7. Notice the brake hard line. It was cut shorter to reach the brake hose
rather than having to go all the way to the wheel cylinder.)
- Bolt the modified caliper bracket assembly to the axle housing.
- Install the new 5-lug axles.
- Install the axle "C" clips.
- Install the carrier rod.
- Bolt the carrier rod bolt.
- Bolt the diff cover.
- Fill the pumpkin with gear oil.
- Install the inner brake pad.
- Install the anti-squeak pins
(I think thats what they are for. You can see the pins figure 8.)
- Install the rotor.
- Install the outer brake pad.
- Install the caliper.
- Attach the brake line to the caliper.
- Bleed the brake system.
(Do I need to say add brake fluid?)
- Install the tires.
- Lower the car.
- Enjoy.
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There you have it. If anything went well, you now have something that looks like this. |
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Like I said in the beginning of this article, there are no steps to keep the E-brake functional. If you attempted
to add the E-brake cable caliper brackets, you would have found out that the bracket hit the axle housing where the lower control arms attach. This does not allow the floating caliper design to use the outer
pad (only the inner pad will touch the rotor when the brakes are applied. Yes, I found this out the hard way.) If you want to retain the E-brakes, you might be able to bend the E-brake cable caliper brackets
so they dont his the axle housing. However, I have not done this and Im not 100% sure it will work. As far as which brake cables to use, '84-'86 SVO cables should work. SVOs use the same calipers are Mark
VIIs and the same E-brake handle assembly as Mustangs. Again, Im not 100% sure on this. If you have any questions and/or comments, please E-mail them to derek@wcfords.com. |
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