Drum Brakes and Disc Brakes, A Historical Question

phaeton wrote:


Gawd(s) help you if you try to stop that 1957 Buick Roadmaster after driving through a deep puddle.

Was there a question or a confused statement?

Wait a minute...the steering wheel is big because of differences in braking forces? Huh??? Steering wheels are usually big because the car is heavy and weighs down on large tires.

Who is the they that should have arrived at rack and pinion steering and when should they have done it.

More area than what. The surface area of a disc is pretty generous if you think about it.
But comparing braking or contact area is pointless - drum and disc systems are two fundamentally different designs. One uses a larger braking surface but lower pressure while the other uses a smaller contact surface and higher pressures to accomplish the same end.

Just what exactly is comparative (braking) area anyway. Never heard of that term.

Sure...extreme speed changes on cars with fat high adhesion tires requires a lot of force to be exerted on the wheels.

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John S. wrote:

In this context, a poorly worded statement, sorry. Feel free to disregard it.

This is also related to the previous citation. It's not apparent, but I was comparing non-power-assisted older cars with newer power-assisted cars. However, my whole spiel into steering is admittedly disjointed and makes little sense, so once again, feel free to disregard this statement. ;-)

"They" being auto manufacturers, and 'when' being before the (formerly) traditional steering box-based front suspension/steering systems became the norm. Once again, this is a poorly worded question and statement on my part, and it's actually probably its own topic. I will elaborate if you want me to though.

In this context, i was meaning "drum brake contact area compared to disc brake contact area". Sorry.

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phaeton wrote:

Any comparison of a non-assisted braking system to an ASSISTED braking system with the booster non-functional or disabled is specious. It is FAR harder to stop a car with a dead power brake booster than it is to stop the same car with MANUAL brakes.
As an example- my daily driver is a 1966 Dodge Polara. It originally had power drum brakes that would throw you through the windshield with a feather touch on the pedal. It was fine once you were used to it, but a real shocker if you'd been used to driving another car. It was also a single-cylinder master cylinder, which I consider unacceptable to drive daily- a single blown hose would take out the whole system.
When I gave the car a makeover last year, part of the upgrade was to put on front disk brakes (bolt-on using a '73 New Yorker as a donor car for the spindles, calipers, rotors, and brake lines). At the same time, I got rid of the whole power assist assembly and replaced it with a manual brake pedal linkage from a '65 Dodge 880, hooked to a modern aluminum master cylinder from an 89 Diplomat, with the proportioning valve, safety valve from the Diplomat. So the car now has a fully split braking system, with safety valve to isolate the halves of the system from each other in the event of a blown hose or wheel cylinder, and warning light that comes on when the safety valve has to do its thing. AND it has manual front disk/rear drum brakes. I *love* the brake feel- its more tactile than power boosted brakes and does have a somewhat higher pedal effort, but much lower pedal effort than just disconnecting a power booster. I can bring that big C-body to a stop faster than the ABS and 4-wheel power disks on my wife's 93 Vision TSi can stop that car. About the only gripe I have is that manual brakes demand that the resting height of the brake pedal be a bit higher than power brakes, because there has to be more total pedal travel. Its back to the feel of my '68 Ford and '49 Plymouth from years gone by- you have to slightly LIFT your foot to move it to the brake pedal, rather than just slide it left. No problem once you're used to it, but I am considering putting power brakes back in (using a modern booster) for just that reason. After all, my wife does like to drive that car, too. She doesn't mind the pedal feel at all, but the height does bug her because she had literally never driven a manual-brake car before in her whole life. I learned on manual brakes, so its second nature to me.
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phaeton wrote:

"Total Contact" drum brakes (trade name of either Bendix or Lockheed, I forget who came up with it) are just that. The way both the front and rear shoes pivot allow for both shoes to be in total contact with the drum. Earlier brakes (such as the ones on my '49 Plymouth) had separate wheel cylinders for each shoe, and had more contact at the end that the cylinder activated versus the "heel" end of the shoe. The other problem with this type as opposed to the Total Contact design is that the brake is far less effective when the car is going backwards than forward. Backing up really briskly and slamming on the brakes was always "interesting" in my ol '49.

I have no preference as to how the valves get actuated, and I own both types. OHC has advantages.... if you want to turn the engine over 7000 RPM it has BIG advantages. What chafes me is when magazine writers even CARE how the valves work so long as they work. The abuse the old Jeep 4.0L inline 6 got from magazine writers was unforgivable. It was superior in every way compared to most of the Japanese engines they compared it to, but they always ragged on it because it was an "antiquated pushrod engine," despite the fact that it typically returned better acceleration, better mileage, and had more bottom-end torque for offroad rock-crawling than the competition OR its replacement- the OHC 3.7L v6.
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phaeton wrote:

Not so much the design of the steering mechanism or the difference between SLA and struts - a good recirculating ball steering box is just as good as a good rack and pinion setup, from the driver's perspective; likewise a SLA suspension arguably provides better wheel control than a strut type suspension. Heck, BMW kept using their excellent recirc ball boxes long after everyone else went to R&P and BMW's are renowned for their incredible steering feel and precision. However, back in the day, power steering was always an extra cost option, and cars were designed as such. What this meant was a) the suspension was set up with less caster, to reduce steering effort, and b) the steering *ratio* - i.e. how many degrees the front wheels turned for a given rotation of the steering wheel - was generally set up to provide the driver with more leverage. The first thing that people notice when driving a 50's vintage car is that the steering tends to be a little "numb" (due to the lack of caster) and "slow" (due to the slow ratio) which is just the nature of the beast. And, yes, the steering wheels tended to be large - 17" or even larger, to also give the driver more leverage in slow speed situations. As automakers realized that more and more people were ordering cars with power steering anyway, caster specs were changed and ratios quickened to provide a better experience for the driver, but that made vehicles without power steering almost undriveable unless you had decent upper body strength, so eventually the manual steering option was pretty much dropped across the board except for small, light cars that didn't really need it to begin with.

Based on looking at the wear patterns on the shoes of drum brakes; I would say that it doesn't appear that the front shoe has appreciably less contact area than the rear as a percentage of total lining area, assuming that the brakes are kept in proper adjustment. That said, from a pure physics standpoint, it really doesn't matter how much lining area there is at all; the greater area is only useful when it comes to resisting fade (as is the ability of the drum or rotor to quickly shed heat buildup.) What is important in terms of brake torque, for either system, is the *diameter* of the drum or disc, as the same frictional force will provide a greater torque on a larger diameter drum or disc.
nate
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I think it may have had more to do with design and tooling commitments. Retooling for a totally new system takes time and money. When discs were an option, they were more expensive than drums. Back in the day, if you bought a new car on a budget, you went with the cheaper drums.
I know the AMC Marlin was available with discs in 1967, so you can bet they'd been working on discs at least a couple of years prior.

Front drums were used by all world manufacturers well into the mid'70s, along with single-circuit master cylinders where local laws permitted.
The Japanese, for instance, did not ship us their front drums primarily because they were concerned with up-contenting their vehicles to distinguish them on the American market. This was the same thinking that led them to install reclining seats, radios and resistance-type rear window defoggers as standard at a time when those were options or unavailable at all on North American cars.
--
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The Rambler Marlin came standard with front power disc brakes for the 1965 model year, these were made optional in '66. (Classic and Ambassador models offered discs as an option starting in '65.) This was a four-piston, fixed-caliper Bendix system with solid rotors. A bizarre "non-servo" drum brake setup was used in the rear. (Was supposed to match the discs without use of a proportioning valve. Virtually impossible to get parts for today!)
As I recall, Studebaker offered disc brakes as an option starting in '62 or '63.

Rambler made dual-circuit master cylinders standard on all their models (except Metropolitan, which was on its way out) starting in the 1962 model year. I think Studebaker also did so around this time, and Cadillac as well.

Some Japanese vehicles shipped to the U.S. did indeed come with drum brakes. This was the case with the Subaru 360 and Star/1100 (the latter had inboard front drums), the early Toyota Coronas, as well as early Datsun pickups.
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Roger Blake
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Roger Blake wrote:

Studebaker did the same thing; the rear brakes used were actually based on an old pickup truck brake design. I personally like this arrangement; the lack of a prop valve is just one less item to fail. Studebaker however used dual piston calipers, not the later 4-piston type. I'm guessing that the 4-pots hadn't been introduced yet, but I'm willing to be corrected. Is it possible that the Marlin's rear drums shared parts/design with the Avanti? If so, I might be able to help track down parts sources, if this is of personal concern to you.

late '62, for the '63 model year. Parts were shared with contemporary Jag E-Type. Avantis and "Super" package cars got discs as standard, but since the spindles etc. were shared across all model lines you could order any Studebaker you wanted with disc brakes.

Studebaker introduced them for the '63 model year. Not sure about Cadillac. Oddly enough, Studebaker did *not* use the dual circuit master cylinder on cars equipped with disc brakes; I can understand this on the Hawk series which still used the underfloor master cylinder (dating back to prewar cars) and therefore didn't have a dual circuit master cylinder option at all, but on the Larks and Avantis which used the more modern suspended pedal setup I'm not sure what the reasoning behind this decision was. At some point a dual circuit master cylinder was mandated by a FMVSS, I think about 1967?

So did very early VW Rabbits, for that matter.
nate
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Good point. The real problem with the Bendix non-servo drums used in conjuction with the early Rambler disc brakes is lack of parts. At this point most parts catalogs don't even list them properly, unless you can get to the old printed books. Even so the parts have all been discontinued, can't even get replacement shoes any more let alone the bizarre ratcheting adjuster, etc. (At least shoes can be relined.)

It seems to me that at some point I looked into this and found that they were no interchangeable parts. The standard "fix" at this point for those old Rambler disc systems is to retrofit the brakes from a "modern" 1980s-vintage AMC car (like a Concord). Parts for those are still readily available, probably because they were shared with the Jeep line.

Yes, as I recall 1967 was the first year for federally-mandated dual circuit brakes.
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N8N

I thought it was Jan 1, 1968.
A bunch of new safety regs came in for the 1968 model year. Headrests, 3-point seat belts, side marker lights, door beams, among other things. AFAIK, 1968 models built in 1967 didn't need them, but some makers installed them early anyway.
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I thought it was 1967, but I could be wrong, it was a long time ago and I'm going by my own memory. As I recall that same year the collapsible steering columns came into play, though Ford went with a big cushion in the center of the steering wheel at first. (AMC and Checker purchased the GM collapsible columns.)
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TeGGeR wrote:

Safety regulations came in dribs and drabs at first. The first may have been headlight height restrictions, and the requirement of sealed beams in 1940. I'm not sure when safety glass was first required.
Lap belts were first required in 1965.
The 1968 model year saw a whole whack of regulations all at once, sparked by the furor surrounding Ralph Nader's book from a few years earlier.
--
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Roger Blake wrote:

If it has a ratcheting adjuster, the brakes are NOT the same as a Studebaker. The Studes with front discs used eccentric adjusters behind the shoes. I thought I might be able to help you out, but I guess not.
nate
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Roger Blake wrote:

Imperial had a 4-wheel disk system ( with an odd full-disk caliper) briefly in the 50s. I'm not sure exactly when they started, but I know that in 1966 Budd 4-piston disk brakes were optional on all the full-size Chrysler products (Polara, Monaco, Fury, Newport, 300, New Yorker, Imperial). The midsizes (Belvedere/Satellite, Coronet, Charger) had them optionally no later than '67. Both of those systems are now very hard to get parts for- I considered tring to scare up an original Budd system for my Polara but gave up quickly. Most owners of those cars now retrofit the single-piston Kelsey-Hayes calipers that were standard (and darn near universal) in the 70s and 80s. Cheap, available, work 99% as well as 4-piston brakes anyway. The only real advantage of the 4-piston setup is more even inboard vs. outboard pad wear and more tolerance to warped rotors (not necessarily a good thing- I'd rather feel a warped rotor and FIX it, personally).
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TeGGeR wrote:

Those were the Lambert discs. Not at all like Jaguar's system of 1957. Very odd, and a very interesting concept.
The big problem with the Lamberts was that they used the same hydraulic wheel cylinders used by drum brakes, but operated them at 4 times the usual hydraulic pressure. Apparently fluid ruptures were too common for comfort, so the Lamberts were discontinued.
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That's right, I had forgotten about that. I never really did 'grok' how that system worked. As far as I know the earliest post-war use of disc brakes in the U.S. was in the 1949 Crosley -- however those were basically unmodified aircraft brakes. These would lock up solid due to corrosion when used on salted winter roads.

That's also SOP for the early AMC/Rambler disc brake systems. Retrofitting the single-piston Bendix calipers from 1980s-vintage AMC cars is pretty much a bolt-in operation.
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TeGGeR wrote:

Didn't pretty much every NA manufacturer move to single-piston floating calipers by 1968?

Well there you go. Far from being behind the curve, it now appears American manufacturers had been working on discs pretty much as long as the Europeans had.

...and wasn't even made by AMC, but by the British Motor Corporation of England on BMC's A30 chassis. It was sold as the Austin Metropolitan in the UK.
<snip>

So there were some exceptions to the rule.
The Toyota Corolla was available with front drums as late as 1975, but those were not installed in Canada or the US.
--
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I think AMC used the 4-piston Bendix jobs through 1970, moving to Kelsey-Hayes single-piston floating calipers in 1971, and Bendix single-piston in 1975. (Though my '75 Hornet was built early in the model year and still has the KH brakes.)

The Metropolitan was designed by Nash in the U.S. (actually an outside designer named Bill Flajole). It was determined early on in the Met's design that it would be built overseas to take advantage of lower labor costs and to get around steel shortages in the U.S., Fiat was initially considered, Austin ultimately chosen. There was a book called "The Metropolitan Story" that came out a few years back that goes into the car's history in great detail, and of course much may be found on "thuh web," such as:
http://home.insightbb.com/~hoosiermets/page11.html
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Speaking of Metros..
A friend of mine in HS had about 5 of those. His last name was "Hudson", and he claimed it was one and the same with the Hudson Automobile company that got absorbed into Chrysler. Says his dad was part of the Hudson RnD team and stayed on in Chrysler up into the 70s.
I always thought they were neat little cars, but I don't remember if any of them ran or drove. They were all in a field behind his house, along with some other stuff I have never seen before or since- most notably a set of fuel injection heads for a 440, and a '56 New Yorker with a 392 Hemi prototype in it, a pushbutton transmission, power everything (windows, seats, steering wheel adj, mirror adj, etc) and (of all things) a phonograph that could play 45s.
Btw, this has been an interesting thread to read, with all the historical bits. Thanks to everyone who has chimed in!
-phaeton
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TeGGeR wrote:>

I had a look at that page. And this one: http://en.wikipedia.org/wiki/Nash_Metropolitan
They say nothing about what Nash ended up using as the basis for the Metropolitan. The Wiki page does say the car was built using "existing mechanical components". The Met was built using the Austin A30 chassis and (originally, apparently) the Austin A-series engine. I suspect Bill Flajole ended up contributing little outside of the body styling.
The identical chassis and engine family was used for the original Austin-Healey Sprite, although the original Sprite never received a B-series engine.
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