Buying Into Nanny-State Safety Diktats: Dual-Circuit Brakes For the A100

Murilee Martin
by Murilee Martin
buying into nanny state safety diktats dual circuit brakes for the a100

Ralph Nader’s Unsafe at Any Speed was published in 1965. For the 1967 model year, cars and light trucks sold in the United States were required to have a dual-circuit brake system, so that a single hydraulic leak anywhere in the system would not result in total brake failure. Real drivers knew that they could come to a complete, safe stop using the emergency brake— that’s right, for emergencies— but that wasn’t enough for the feds. They rammed dual-circuit brakes down the throats of the American public, adding at least several dozen dollars to the cost of a new car. My Dodge van is a ’66 model, which means it was the last year for the single-circuit brakes that gave our forefathers their moral strength (though not as much strength as their forefathers, who relied on mechanical brake actuation instead of hydraulics), and a lifetime steeped in Naderite propaganda has convinced me that I’m better off with some margin of hydraulic safety. Upgrade time!

Rocket Surgery Racing Renault 4CV team captain Rich gave me a coupon for brake-line assistance for my birthday, so I decided it was time to take him up on the offer.

The new 1967-grade dual-circuit master cylinder cost well under 50 bucks, and new brake hoses plus some line and fittings didn’t add much more to the cost of the project. This would be an all-sweat deal.

More sweat than we expected, because the A100’s forward-control setup necessitates a funky linkage-and-backward-mounted-master system. The master cylinder, which is actuated by a system of rods and pivots that appear to have been adapted from a piece of 1897 mining equipment, is located directly below the driver’s seat.

I’d assumed that Chrysler, once all their lobbyists had failed to fend off the dual-circuit brake demands of the US government— headed by arch-liberal integrationist Lyndon Johnson at the time, as if I needed to spell that out for you— would have found some cheap, bolt-in way of installing the slightly longer dual-circuit master cylinder, but it turned out that the ’66 master cylinder’s tack-welded-in-place splash shield didn’t have room for the ’67-and-up components.

So, the Sawzall had to be brought into play. This involved jarring loose 45 years of built-up crud, not to mention the opportunity to slice important stuff ranging from the wiring harness to the throttle cable.

Hacking this piece of sheet metal away means that some air destined for the radiator will slip past, so I might fabricate a replacement that fits the new master. I’ll see what happens when summer heat comes along; for now, the engine runs quite cool with this small opening next to the radiator.

With the help of a $2.99 tube bender and some coat-hanger wire as a template, Rich starts work on the replacement brake lines.

I’ve never been able to do a double flare correctly, in spite of several very frustrating afternoons spent trying to do so in the past, so here’s the part I was especially glad to have Rich take on.

Modifying the plumbing was pretty straightforward; plug one port on the original four-way tee that once split the line from the master cylinder into one line to each front corner and one to the rears, using it for the front circuit only. Add another tee to send pressure to the rear brakes and signal pressure to the hydraulically-actuated brake light switch.

Bench-bleeding the new master cylinder.

To add fluid to the master cylinder in an A100, you must remove an access panel located on the floor just in front of the driver’s seat. Naturally, the access panel doesn’t quite fit the larger dual-circuit master cylinder, so a funnel must be used to get fluid to the rear reservoir. This process got brake fluid all over everything beneath, which made finding leaks a real challenge.

I didn’t trust the parked-for-12-years brake hoses, so I sprang for new ones all the way around.

After some bleeding, the new setup works fine. I’ll probably convert to front discs at some point, but for now I’m satisfied with drums that are less likely to fail. Anybody want to buy a genuine single-circuit A100 master cylinder?

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3 of 48 comments
  • MrFixit1599 MrFixit1599 on Mar 24, 2011

    On my 1981 Subaru GL, the Emergency Brake was actually connected to the front brakes. Sadly, if the brake pads decide to remove themselves from the front drivers side caliper (due to damage from a previous offroad excursion), not only will the regular brakes not work worth a damn, neither will the Emergency Brake. Needless to say this caused an airborn offroad excursion. Still drove the damn thing about a mile home with a nice trail of oil and antifreeze behind me.

    • MarcKyle64 MarcKyle64 on Mar 24, 2011

      Ah yes, the Subaru HillHolder emergency brake. It would activate a little valve in the master cylinder that held the brake pressure until the clutch pedal was released. It was quite handy on hills where you wanted a hand on the wheel and the other on the shifter.

  • Kevin Kevin on Feb 21, 2023

    I just saw this article 12 years after the fact when looking online to confirm that dual-circuit master cylinders were required starting in 1967. Please tell me that that first paragraph is a sick joke. These cars don't have "emergency" brakes. They have parking brakes, and if you've ever tried to stop by smashing the little pedal on the far left, you know that it does basically nothing. Yeah, if you're on an open road with several hundred feet of clear space ahead of you, you can stop safely, but if you're in traffic, you better jam into into first gear and pray.

  • Inside Looking Out Enforcing laws? It is so yesterday! Welcome to California!
  • Lou_BC You'd think cops would have an understanding of the laws they are supposed to enforce.
  • Merlyn I’m on my second Spark and love it! I can pass any car I’ve never had a problem going up a hill it does just fine. As for cargo I can fit three suitcases, two book bags and still have the front seat for a passenger. Not sure what point this guy is trying to make. I have hand free phone service and Sirius radio plug in my phone and have navigation. I would buy another spark in a heartbeat.
  • Buickman I won't own one and I'll be happy!
  • Jeanbaptiste Ever since y’all started sending your damn geese down here we’re just been waiting for one of you to show up.