Bubble flares are different from double flares, and if you try to put a bubble-flared male fitting into a female fitting that wants a double flare, well, that’s on you.
Such are the things one learns when plumbing a 550 Spyder.
After bending up some fuel lines earlier this week I turned my attention to the clutch and brake lines, steel tubes expected to endure high-pressure without leaking. Helpfully, the car came with a big box of lines and fittings . . .
…which meant all I had to do was sort through them and figure out which ones went where.
There was another box with flexible brake hoses, plus the clutch slave cylinder and an array of proportioning valves and other sundries. 
I started with the clutch because it seemed easier.
After drilling out small holes in the bulkheads and firewalls, I ran the longest hard line I had clear to the back of the car and into the engine compartment. 
It wouldn’t reach the slave cylinder, so I found a male-male connector in the kit that seemed right to link a shorter piece.
But then I ran into trouble: The flared fittings on my medium-length tubes would not screw into the fitting on the clutch slave.
Consulting the build manual I learned this important fact: It’s not supposed to fit.
There is supposed to be an adaptor fitting. TWO, actually: one for the master, one for the slave. Turns out the CNC parts want double-flared (USA style) fittings, not bubble-flared German ones, like VWs like.
There were no adaptor fittings with the pile of car parts I’d bought.
So I searched around the shop for other stuff and found:
A coffee can full of brass junk! Part of the cache of trash I liberated from the great Dr. Clock’s First Going Out of Business Sale last year. I figured something in there ought to fit, and I was right.
There was one piece. One adaptor.
Reading the build manual I learned that many parts shipped with the kit were technically incompatible. The proportioning valve, for example, requires double flares. The 2-pound residual valves, of which I was supplied four, apparently don’t. But I also probably don’t need them, as they were meant to give a little pressure to the front disc brakes, to keep them coming on first. With rear drums and front discs, according to the manual, the back brakes will lock up first unless the fronts get the residuals. Since this car has four-wheel discs, it seems unlikely. So either all four brakes should get them or none. So I chose, for now at least, none.
But anyway. What I had was an array of hard lines and stainless braided and rubber coated brake lines that all featured metric threads and bubble flares at both ends, and only a couple with 3/16-inch double flares. So I needed to cut some line, lose some fittings and make some flares.
- Left: bubble flare, metric threads. Right: double flare, USA threads.
After finding a tube that fit my slave cylinder I took it, and the longer metric line I wanted to use, over to the bench for some surgery.
This seems to fit perfectly. I’m still going to keep my fingers crossed when I fill the reservoirs and test it later. Wish me luck!
I did not want to pull out the long line after I’d already bent it to the master cylinder, so I fit my adaptor piece on that end. They say to fix the adaptor to the component with red threadlock, so.
Having cracked the flaring code, the more-complicated braking system went together a little quicker and easier. One pretty long line from the rear of the MC into the tub, ending near the firewall with a double flare for the proportioning valve. Then a shorter piece with a double flare from the proportioning valve, to the T junction, which wants the bubble flare. Then all bubble flares to each caliper.
On the originals, the brake lines route along the frame rails and then jump to the middle of each axle tube with a flex line, where they join hard lines to the brake drums. After consulting with a friend who owns a Vintage Spyder, I decided to route the lines along the torsion arms instead. This is mainly because the brackets on the frame and axles would put the brake lines very close to the exhaust. Brake fluid doesn’t like heat.
Even with all those hard lines, I had to break into a kit of VW Bug lines I’d bought years earlier for Bridget.
Roughed-in fairly neat. I’ll bolt down the T fitting later and fab-up some loops for the far ends of the braided lines. Or just cut the ones off the axles and weld them to the torsion arms…
The lines from the MCs look fairly neat too.
So now it’s down to tightening everything up, plumbing the reservoirs and bleeding the system to see where my mistakes are. Not a bad five hours’, all-in-all.
Along Came A Spyder 