Tuesday, July 24, 2012

Rear Disc Brake Fitting, Brake Lines & Coilover Mount Bushings

As the rear axle evolution progresses, I am becoming more and more happy with the results.  After a few nights of diligent work, I am to the point where I will start prepping the axle housing for final color very soon, and that will make way for the final modifications to the 4-link suspension.  However, before I get too far in that description, there are a few interesting things I need to document here first.
“Cunifer” Hard Lines
Pronounced “Cue•knee•fur” – the word cunifer is actually an acronym referring to the metallic composition of the brake line tubing most people have never heard of.  Specifically, cunifer tubing is an alloy of copper (Cu), nickel (Ni) and iron (Fe) and has been around for over 70 years.  The material is extremely corrosion resistant, bends and flares very easily, and is very durable.  And while the material is a copper-based alloy it is NOT conventional copper plumbing tubing in any way, shape or form.
In hot rod circles, stainless tubing gets big play because it’s shiny, durable, and obviously corrosion resistant.  The good news is that many pre-bent brake line kits are available in stainless for restoration ease as well.  But what if you are doing something from scratch or want to clean-up the appearance of the installation over what the factory installed?  In most cases, you are on your own, and generally speaking, stainless steel brake tubing is harder to work with and expensive, especially for the do-it-yourself restoration enthusiast.  In fact, other than “off-the-roll” appearance, there really isn’t any advantage to stainless steel brake line material compared to cunifer. 
When was the last time you saw stainless steel brake lines on a production car?  Even an exotic, high-end sports car for that matter?  Fact is, in 99% of brake applications, they don’t use stainless brake tubing.  In fact, more high-market car manufacturers use cunifer tubing than any other.  Rolls-Royce, Porsche, Audi, Aston Martin, and Volvo all use cunifer brake line tubing exclusively.  Japanese and US car manufacturers are the remaining hold-outs that continue to use conventional coated steel (not stainless) tubing due to the pervasive “low-bidder” mentality that dominates these markets.
Luckily, cunifer tubing is easy to get in the aftermarket and is priced between plain coated steel and stainless steel tubing.  It can be easily polished to a copper-silver shine (if that’s what you like) and will accept all standard brake hardware.  Due to cunifer tubing’s slightly softer surface than steel, an additional measure that should be taken is that the outer surface of the cunifer tubing should be protected with a stainless steel spring shield to avoid damage from rocks and road debris.  Plus it looks kinda cool as well!  I have chosen cunifer tubing as the preferred material for all of my fluid hard lines in the Boss and formed the rear axle hard line using this material.  I will be using much more of this material as I move forward in routing new brake hard lines around the rest of the car and will likely use it for the fuel hard lines as well.  In any case, it’s worth a look.

Cunifer brake tubing is wonderfully easy to form with simple tools.  Note the protective stainless steel spring around the tubing to prevent damage from road debris.
Here is the rear brake distribution block with the newly formed cunifer hard line in place.
The hard line is routed around the periphery of the 3rd member for a clean look.

Here is a look at the passenger side of the hard line.  Bends are smooth with no hint of kinks.

Rear Disc Brake Trial Fit
As the modifications to the axle housing approach completion, the time had finally come to trial fit all of the Street or Track, LLC rear disc brake conversion parts I had collected for the car to ensure everything fit as intended and clearance issues could be addressed before applying final finishes to the rest of the parts.  This would also mark the first time I could test fit the axles and complete set of brake lines to the housing as well.
I am happy to say that the brake kits installed quite nicely and the installation instructions were quite easy to follow.  I played with caliper position a bit but quickly discovered there was only one position that would allow adequate clearance to all components, so that’s what I stayed with.
Once I was satisfied with the caliper installation, I fit all of the rear brake lines (hard and soft) to ensure proper fit.  Here again, the Street or Track parts worked superbly and I could now move forward with final prep of the housing before sand blasting and coating.
This is the Street or Track rear disk brake kit mocked up on the left rear of the axle housing.  This is the "busiest" corner of the car and I discovered the fit to be perfect for my 4-link suspension.

here is the left rear brake kit installed (without brake pads).

The right rear brake kit is equally nice an installation and a considerably less crowded corner than the left.

Left rear disc brake conversion mock up is complete!

Coilover Lower Mount Bushings
In the process of engineering the upgrades to the 4-link rear suspension I am installing, I moved to a custom made Bilstein damper.  In doing so, the mounting fastener diameter went from 5/8” to ½”, which necessitated bushing the mounting holes in the axle brackets down to the proper size.  As luck would have it, I found commercially available bushings at a local hardware store that fit the bill perfectly.  With a quick pass of a 5/8” drill through each hole, the bushings slipped right in and I was able to weld them in with little trouble.  Another quick pass with a ½” drill and the lower mounts were ready for action.  Check!

Using a commercially available bushing, I was able to weld it into the original 5/8" mounting holes.  This was necessary to mount the new Bilstein coilover dampers as they use 1/2" fasteners instead.

Going Forward
Now that the mechanics of the axle housing are basically complete, my next area of concentration will be to finish modifying the rear trailing arms and fabricating the spacers required to properly locate the spherical rod ends that will replace the rubber bushings they were originally configured with (yuck!).  Following that, and a few more trial fits, the axle housing should be ready for color and the brakes can be finally fit.  By this time, Fall should be approaching and the focus will shift back to the rear bodywork area and then the fitting of the front coilover suspension.  Busy winter ahead!  …….and still a few surprises to come!


  1. The whole rear diff is looking good. Did the brake line come with the SS cover or did you get that separately and slip it over the lines before you bent them? I like the looks of that a lot. As usual, your quality work is outstanding.

  2. Howdy Dennis!

    The stainless protection spring is slid over the tubing after bending and during final finish before the last tube nut and flare is completed. I too like the look of it and it adds a bit of peace-of-mind to boot. I think all of the hard lines in the car will get this treatment by the time I'm done. Can't wait to get the housing in final color!