Rear Disc Brake conversion for a Ford Escort live axle rear end
I've finally got around to fitting the rear calipers and
updating this site.
Doing a rear disc conversion on a live axle Escort diff is a bit tricky, but certainly not impossible. Some careful browsing of various disc brake manufacturers websites (such as www.dba.com.au and www.brembo.com ) reveal certain parts off other cars that suit nicely.
Firstly I choose rear calipers off a 1987 Nissan Skyline R31. A Nissan Pintara from the same vintage will also suit. These are a single piston caliper with an integrated handbrake, which is necessary when doing a rear disc conversion. Some cars with rear discs use a small drum brake for the handbrake, however that just adds complexity to the conversion for this purpose. The R31 rear calipers are also used by Westfield on their independant rear suspension models, so they obviously suit the car.
Disc rotors are the next part to choose. The important thing here is to pick one that has the same bolt pattern as the Escort rear end, namely 4 stud on a 108mm Pitch Circle Diameter. Another issue in this particular application to find a rotor with a very large hub face so it can fit over the standard Escort flange on the axle. There seemed to be only one choice and that was from the rear of a Audi 90. They are also only around 9mm thick which is perfect for the R31 calipers. They can't take a vented rotor as the channel is not wide enough.
The Audi rotors need a little bit of work to fit. You need to mill around 0.5mm from the inside of the rotor hub face to clear the Escort flange. Alternatively you can remove the axle from the differential housing and trim around the same amount from the flange itself in a lathe. The other custom modification is the creation of a set of hubcentric rings. These are necessary as the hub bore on the Audi rotors is around 67.5mm and the Escort is 64mm. Their job is to sit between the hub and the rotor to ensure the rotor is perfectly centred. Failure to do this will lead to some nasty vibration and probably brake failure, so take note.
Due to the width of the hub face on my alloy wheels, I also took the caution of buying and fitting a set of extended length wheel studs, as I was only getting around 5-6 threads of stud in my wheel nut. Now there is no doubt, with the stud extending past the nut!
Once the rotors are bolted on, its time for the boring part. Measuring. Tape measures and rulers will not cut it, you really need precision measuring equipment such as dial gauges and vernier calipers. My measurements were:
* 96.5mm between caliper mounting holes
* 70.4mm between axle flange mounting holes
* 45.1mm horizontal between sets of holes.
* 2.0mm offset towards the centre of the vehicle
Note, you should verify your measurements. This fits my Escort Mk2 rear differential/axle. It may not fit Mk1 or even some Mk2s.
After you have taken all your measurements, its time to draw up the bracket. I use AutoCAD personally, but there are plenty of free CAD packages available online ( CADStd is one), alternatively you purchase an older version of AutoCAD cheaply from Ebay.
You have a choice here, on whether to get your brackets professional milled, or you can have a shot yourself. Keep in mind that you will need to be working with 5mm steel or aluminium plate, so its hard going by hand, and perhaps somewhat inaccurately. In the pictures below, I made my prototype from thinner ally plate just to test fit. My final brackets are milled by CNC (computerised) from 5mm mild steel plate. I've choosen steel as I want to weld the bracket to the axle housing as well as bolt it for extra piece of mind. My TIG invertor welder can't do aluminium.
Anyway once the brackets are complete simply bolt it all together.
Here are the pictures of my prototype fitting. Pictures of my final, welded installation will be uploaded soon, as my digital camera is currently on loan to a family member.