A Different Kind of Disc Brake: 1949 Chrysler (2023)

The start of America's automotive golden age was ripe with innovation. You could buy a car in 1964 with methanol injection! They had turbos 20 years before Saab!

Unfortunately for America, Europe's scarcity cars were not fit for her market, so Detroit had very little competition. They also had no resource constraints. Once certain dimensions of consumer preference settled, Detroit coasted.

Europe and Japan were poor, so they had to work to make good cars. They were also culturally open to each other.

Then, one day in the 90s, Detroit woke up dead.

The hassle is a bunch of things:

1. The knowledge of how to deal with hydraulics across the industry is slowly accumulating. We've been fixing bikes with bowden cables for a hundred years give or take a bit. We've been dealing with hydraulics for 25 years give or take a few, and it's a really recent development that they've trickled down to the low end of the market and penetrated the road market at all. The knowledge of how to fix them is not as widespread as you'd think.

2. Compounding the above, we have two competing systems (naturally). SRAM runs DOT fluid and Shimano runs mineral oil. The bleeding procedures are different (naturally). Surprisingly, the hygroscopic nature of DOT fluid is a non-issue. Both systems run hard for a year are basically due for a fluid change.

2.5. Some of the bleed procedures are consistent within a manufacturer's line over time. Often times they are not. Step one of a bleed is usually RTFM because the brakes you're looking at are probably different from the last three sets you've done.

3. Everything is small. The entire master cylinder assembly has to fit inside the brake lever. On a road bike, your hand wraps around all of that, plus the shift mechanism. Access to the reservoir cap, which is also the bleed port is about as good as they can make it, but it's still one more damn thing to peel back the rubber hood.

4. The calipers are similarly small, leaving less room for sealing, etc.

5. There's little room for manufacturing variation in the mounts as well. In theory this would affect mechanical disc brakes as well. In practice, they hold up better when the caliper is mounted cockeyed. Park Tool makes an extremely elaborate facing kit to rectify problems with mounts. The shop I work at part-time has one, and I've had to use it. The fact that the rotor is non-rigid does buy you some tolerance back, but sometimes it isn't enough.

All of the above adds up to a lot more hassle than mechanical disc brakes not because it's insurmountably hard to do the work. The major factor is that a good set of mechanicals is so damn simple and reliable. The set on my mountain bike has 7000 miles of touring, plus mountain biking, and I doubt I've spent cumulatively 3 hours working on them.

I go to pains to not mention torque, because I'm not talking about that. I'm talking about the physical pressure exerted by the pads on to the surrounding structure. The forces involved even when the vehicle is not moving.

The american car industry took a deep nose dive because the cars they were building in the 70s and 80s struggled to crack 100,000 miles without a major issue, and the interiors literally fell apart in your hands. I'll never buy a GM or Ford because I grew up in them and the door handles were falling off and stuffing was shooting out of the splits in the seats. The paint not even 10 years old was so oxidized it would rub off on your clothes if you rubbed against it. If GM and Ford are better now, I wouldn't know because I haven't been in one in literal decades. The only reason they're still around today is the chicken tax (it's a real thing, look it up) and the fact that you can't buy a full size car anymore outside of marques like the Mercedes S class and BMW 7 series and a handful of others, largely top end halo cars.

From the diagrams alone, it looks like a giant maintenance nightmare, compared to a dead simple rotor, with a simple caliper sitting on it.

It looks as if it may have had some weird dynamics also, that would be confusing to a driver used to regular brakes.

Was there a post-war complication trend in engineering?