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The Grand Guide to Realistic American Cars


Concerning 1960s Suspension and Carburetor Tuning:

So it was brought to my attention that I am fallible person and said something erroneous on these two fronts which I was aware from the start of this was probably going to happen. Thus, I had do some investigation.

And that investigation led me down a bit of a rabbit hole that needs more than just a few quick sentences to do justice.

Susepension Tuning:

The big scruple here is progressive versus standard rate springs and its not exactly a simple question that has straightforward answers, if for no other reason than most discussion around this subject has to do with modern hot rodding and off-roading. But these things themselves are a discussion worth having and shed light on the true history of these design choices.

First off. What are progressive and standard rate springs?

  • Standard rate springs can be most succinctly described as springs which are described perfectly by Hooke’s Law - F = kx. The non-technical version of that is that the spring rate is fixed and the displacement of the spring is directly proportional to force applied. If you apply say 1 N of force to a standard rate spring and it compresses 1 cm, then if you apply 1 more N of force it will compress 1 more centimeter. So with this same spring if you applied 50 N of force, it would compress 50 cm. Simple.

  • Progressive rate springs are springs which are NOT described perfectly by Hooke’s Law. Their spring rate varies throughout their travel, getting stiffer as they are compressed more. This means that if you apply 1 N of force and the spring compresses 1 cm, it will NOT compress exactly 1 cm more if you apply 1 more N of force; it will compress somewhat less.

    • Most springs used in automotive are not truly progressive, meaning their spring rate does not vary continuously. Reason being, true progressive rate springs are hard to manufacture. Instead, most “progressive” springs have two or more set spring rates built into one spring and these engage at set points in the travel.

But anyways. Why would you use one versus the other?

  • Progressive springs are very suitable to off-roading, commercial trucks, and heavily comfort-oriented vehicles. The reason is that spring rate changes with the mass of the vehicle. With standard springs, the locked spring rate must be made hard to cope with heavy loads or soft to give comfort but these two are mutually exclusive. Comfortable suspension can’t take loads and heavy duty suspension can’t be comfortable. But with more than one spring rate, this allows for an unloaded vehicle to maintain similar ride quality to a fully loaded one. The variable rate also allows a vehicle to take small bumps with and irregularities on the driving surface with a nice soft spring rate and switch over to harder rate when pushed for handling or into more adverse conditions.

  • Standard springs are cheap and easy to manufacture. And they also tend to give more consistent handling since the multiple rates of progressive springs makes them hard to correctly dampen. Also, with a switch between softer and harder rate, progressive springs often upset weight transfer and make for a more vague road feel.

And finally the question to be answered. Which to use?

In general: standard rate springs

Progressive springs would be seen as an option on trucks and heavily offroad-oriented vehicles. Sometimes also on luxury cars. But standard rate springs were – from what I can tell – by far the most common spring type in suspension design until the 1980s, when they started to become standard equipment on premium and luxury cars. In fact even on cars today, standard rate springs are still very common.

Its also worth noting here that leaf springs lend themselves to easy manufacture of a progressive rate, which is I suspect is part of why Chrysler held onto their leaf spring designs into the 1970s.

Just a few other fun tidbits here:

  • Part of the actual theory of suspension design in the early to mid 20th century was the theory of so-called “natural frequencies”. It was assumed that by approximating the oscillation frequency created by walking, people would feel very secure. Most humans walk at between 70 and 90 paces per minute creating a side-to-side oscillation frequency of about 1.1 to 1.5 hz, hence the very soft tuning of many old suspension designs.

  • It turns out that humans are actually quite a bit more tolerant and can find up to and including 2.0 hz full body oscillations perfectly comfortable which is part of why newer designs don’t go to the same extremes of softness.

  • Motion sickness on the other hand is induced by oscillations between about 30 and 50 cycles per minute or about 0.5 - 0.9 hz. So make sure not to go below 1.0 Hz on suspension tuning or the ride will be somewhat… vomit inducing.

Carburetor Tuning:

Like springs, this also gets into the whole theory of operation on this system and there are never straightforward answers. There is one thing that I want you to remember though before we even get started:

Carburetors virtually always run rich.

How rich? The simple answer is VERY! The long answer is well… this is where the theory comes in to play.

So for performance tune 4 barrel carburetors, its not actually out of the question for AFR to reach as high as 12.5:1 at wide open throttle. Dead serious. Some tunes will go all the way to 12 and above, which depending on your engine and application could be perfectly acceptable.

The bold bits about four barrel carbs and wide open throttle are especially important here because the actual truth about carburetors is that they are NOT fixed AFR machines in multi-barrel configurations. See, the reason you add barrels onto the carb is to make them work better at a range of throttle positions and engine speeds. To understand why, lets talk about single barrel carbs for a second.

Single barrel carburetors are as basic as carbs get. They are a single venturi with a single jet system and because of this they pretty much do have one AFR. This is because the size of fuel jet in the venturi of a carburetor is what determines the AFR, so if you only have one jet, you have one AFR. The problem with this is that during hard acceleration, you want a rich fuel mixture for more power, and for cruising you want a lean fuel mixture for economy. Well, there is only one set of jets so you just sorta have to compromise with a single barrel carb and go for the middle ground between stoichiometric optimal of 14.7:1 and acceleration optimal of around 12.5:1, probably somewhere around 13.4:1.

Now, how do you overcome this limitation? What if we had a separate set of jets for acceleration and a seperate set of jets for cruising? This is the wisdom of the 2 and 4 barrel carburetor. At idle and at cruise, half of the barrels of the carburetor are not open. The primary openings have a set of jets optimized for crusing, producing an AFR usually somewhere between 14.0:1 and 13.0:1 – and yes its still a little rich; I will get to that in a second. Meanwhile the secondary openings will open when the engine is pulling a lot of air into it like when you smash the accelerator and they have a different set of jets which will push the AFR up the desired 12.5:1 range for acceleration. So you get the best of both worlds: economy and power.

But carburetors have one important thing they still need to overcome - intake manifolds. See, fuel delivery is to cylinders as a hose is to a bucket. If you want to fill the bucket accurately and precisely, bring your hose close to it. Carburetors are not close to the cylinders though; its like trying to fill a bucket with a hose from 5 meters away. A lot of fuel just condesates on the manifold. Furthermore, some cylinders are further from the carburetor than others meaning they receive a leaner mixture. So in order to keep every cylinder happy about its AFR and keep it from detonating, you have to run your mixture rich. This right here is why carburetors almost always run rich.

Stoichimetric carburetor tuning is strictly speaking possible but its impractical especially in road car applications where the a perfect AFR would lead to bad acceleration and stalling due to one other critical hurtle for carburetors. When the throttle blades first open, fuel doesn’t just instantly move. Suction from the air has to overcome the inertia of the fuel which leads to an instantaneous lean-out of the mixture. This lean-out condition will cause a drop in power or even an engine stall. Accelerator pump circuits, which add fuel in a quick burst during initial acceleration, do alleviate this problem but not entirely and the ultimate solution is just to keep running a little rich.

So given all of these things, what does that mean for realistic carburetor tuning? You should generally be sitting close to the 13.0:1. Guidelines:

  • 4 barrel performance tuned carbs will be pushing DEEP into 12:1 AFR territory. 12.5:1 is a sorta hot rodder optimal.
  • 2 barrel and 4-barrel economy carburetors will probably see AFRs somewhere between about 13.5 and 12.5 to one. Generally a 2 barrel should use a less aggressive AFR than a 4-barrel since it sacrifices more by having a rich fuel mixture than a 4 barrel does
  • Single barrel carburetors will somewhere around 13.5:1 but probably never go into the 14s.


A point regarding carburetors is the design of the intake manifold. The air passages to the cylinders often aren’t direct but rather follow a criss cross pattern. The idea being to keep the same distance between each cylinder and the carburetor. This isn’t a perfect solution but it does alleviate it somewhat. The design of the manifold is also to allow the air and fuel to atomize before reaching the cylinder. One drawback is that said design isn’t optimal for maximum air flow. It wasn’t until the development of multi-point injection that intakes were designed solely for optimal air flow.


Since I was having to come back to this thread every time I’ve decided to tweak with my 60’s line’s car, I’ve put a “quick” guide together, with the informations from this thread. Thanks kmBlaine for the info!

Panel Material: Steel (Aluminium on cargo vans and sports cars)
Chassis type: Ladder (Unibody on small/pony cars)
Chassis Material: Steel
Engine Placement: Front Longitudinal (Mid Longitudinal on race cars)
Front Suspension: Double Wishbone (Solid axle leaf on trucks/vans, coil on jeeps)
Rear Suspension: Solid Axle (Double Wishbone for sports cars)

Engine Block: Straight 6 or 90º V8
Block Material: Cast Iron
Displacement: 3 to 4.5l for I6, 4 to 8l for V8, 5 to 15 mm larger bore than stroke
Head and Valves: Pushrod, 2 valves
Head Material: Cast Iron (Maybe Aluminium on race cars)

Crank: Cast Iron Crossplane

Valvetrain quality may be raised.

Fuel System: Carburetor
Configuration: 1 BBL - base I6, 2 BBL - common I6 and V8, 4 BBL - high trim, 2x4 or 3x2 BBL - high performance
Fuel: Super Leaded - 98 RON
Fuel Mixture: Racing 4 BBL - 11.8:1, Performance 4 BBL - 12:1, 2 and 4 BBL economy - 13.5:1 to 12.5:1, 1BBL - 13.5:1
RPM Limit: 4000 to 5000 RPM for common engines, 6000 rpm for sport motors

Drive Type: Longitudinal RWD (Optional 4X4 to off-roaders and upper trim trucks)
Gearbox: 3 speed manual: Base for most cars
4 speed manual: Optional for high performance luxury cars, base for high-end sports, optional for others.
5 speed manual: Race cars only
2 speed automatic: Optional on small and mid-size, and entry level large cars.
3 speed automatic: Base for luxury cars, optional on others.

Top speed: Final drive gears between 2,5:1 to 4.0:1, shorter for trucks/off-roaders
Spacing: Tight, below 70
Differentials: Open as default, lockers for tow packages

Tyre Type: By target market
Tyre Choice: Usually Hard Long Life
Tire Width: 165 - 185 mm for compact cars
185 - 205 mm for mid size cars
205 - 225 mm for full size cars
215+ mm for limousines
Parameters: 13" for compact cars
14" for mid/full size cars
15" for limousines
15",16",18" for trucks and off-roaders
1"+ optional for all classes
80-90 sidewalls
Rim Material: Steel, Mag/Alloy optional on high performance cars

Brakes: 2SL front, SLS rear, front discs optional on late 60s
Sizes: 250-275 mm

Interior: Bench seats rear, Bench or bucket front
Entretaintment: Entry: Radios not standard until the late 60s. Optional mid/large cars in early 1960s,small in the mid 60s.
Stick the Basic or Standard radio options
Premium: Radios not standard until the mid 1960s. Generally optional in the early years.
Stick to Standard or Premium radio options
Luxury: Radios standard even in the early years. 8-track started becoming optional in the late 1960s.
Stick to Luxury options

Steering: Manual as standart on small cars, hidraulic as optional, standart on mid/large cars circa 1963

Springs: Standart, progressive optional on trucks, off-roaders and commercial vehicles.
Dampers: Twin-Tube, Gas Monotube optional on sports cars
Sway Bars Tuned to 0% at rear(non existent),maybe existent on front to induce understeer
Springs: Around 1.0 Hz spring frequency. NEVER BELOW 1.0 Hz
Dampers: 0.2 - 0.3 dampening coeficients



The Fighting '40s

The 1940s is an interesting era for cars of all nationalities. It was an era of a lot of experiments, some successful like the Traction Avant and some failures like Crosley. This is the era where cars began emerging from their extremely primitive roots and started to look like and be designed like the machines we know today.

Unfortunately, because this decade is a major changeover point and because the first half was consumed by a massive World War II, some ancient technologies that would have probably been ditched in the early years stayed around well into the 1950s. This was because all car manufacture ceased in 1943, 1944, and 1945 in the United States as the automakers’ were conscripted into making tanks, airplanes, and trucks for the war effort. No production, no new designs, no progress. Until late 1948, US automakers were still selling cars that were essentially mid to late 1930s designs.

What does this mean for automation? You are actually going to have a hard time making truly realistic cars from this era, but you can still come close.

Also, because of how many technologies and design practices arose or went dodo in this era, this is going to be a VERY trivia heavy post.

Platform and Chassis

Even despite cars really coming of age in the 1930s and 1940s, they were still primitive. This is likely would you would see of a typical, if slightly outdated, American car in the 1940s.

Panel Materials:

Steel. Nuff said.

I am not aware of any American car that uses aluminium for its body work in the 1940s. However here is something you WOULD see an car body made out of – wood.

Nope not joking. 100% serious. Have you ever heard the term “woodie” used for a station wagon / estate car? This is where it comes from. Old station wagon designs before about 1950 often used wood paneling so they got dubbed “woodies”. Incidentally, this is why the Chevrolet Suburban (and yes that nameplate has been around since the 1930s believe it or not) was a big deal. The Suburban was the first popular, mass produced station wagon design to use steel paneling, meaning it was exceedingly durable and could take a lot more abuse than the classic woodies. And of course trucks would have often have wooden beds as well.

Now wood is lighter than steel, obviously, so if you are trying to simulate wooden body work, aluminium paneling might be an appropriate choice.

Chassis Type:

Virtually all American cars of the 1940s were of the body-on-frame construction using ladder chassis. Spaceframe could be justified if you are going for something small / limited production.

Interestingly enough, the first American unibody car is actually produced in this era: the Nash 600. The car’s unique construction (for this era at least) made it lighter than other cars and so it got better fuel economy. How much better? Well Nash claimed 30 MPG which combined with its 20 gallon tank would mean a 600 mile range, hence the name “600”. I would be skeptical of these figures though. Just saying.

Chassis Material:

Steel. Again, nuff said.

Galvanized steel might be seen on some trucks.


Dependent front suspension designs weren’t dead yet. Early 1940s designs still sometimes had solid axles in the front. Coil versus leaf spring depends on manufacturer preference – both were used – so that’s up to you. However leaf springs were the more common choice because of their simplicity.

Independent front suspensions had become commonplace on premium and luxury vehicles and were making their way in to many standard designs as well. Double wishbone is all that automation has to offer which is fine considering it was a commonly used design. But in the early 1940s at least, another common design is one which we DON’T have access to, which is the Dubonnet suspension, also called the “knee-action” suspension by GM. Essentially its a trailing link design that uses a coil spring.

Anyways, independent front suspensions were common on luxury cars and had alreayd made good headway into standard cars at the start of this era.

Rear suspensions on the other hand were exclusively solid axle. If someone can point me to an American design with an independent rear, I would be very surprised.

The Engines

Engines are by far one of the most interesting things about 1940s American cars because unlike the 1950s, 1960s, and 1970s, engine design wasn’t considered a solved problem yet. Any of the following were seen in American designs, commonly even:

  • Straight-4
  • Straight-6
  • 90 degree V8
  • V12
  • And yes even V16s :crazy_face:

And here is an exceedingly common 1940s American engine that you can’t build in Automation :frowning_face:

  • The glorious Straight-8

Ahhh! Tell me that doesn’t just have a nice ring to it… “straight eight.”

As far as exceptions go, well, none really. 1940s American cars had a broad gamut of engines as we have seen above. Pretty much the only thing you wouldn’t see – to my knowledge anyways – would be boxers.

Which to use in what kind of car:

  • Straight-4 would make an excellent entry level engine. This was most commonly used by Willys Overland, makers of the world famous Willys MB “Jeep”. Used in their entry-level trucks and passenger cars. Also the only engine used by one very odd American manufacturer, Crosley, which was making cars one might confuse for a Renault, Citroen, or Volkswagen because they were tiny and that is not even by American standards.

  • Straight-6 should be your go-to design for a typical 1940s American car. This was the base engine on virtually everything, cars and trucks alike, made by the Big Three (Ford, GM, Chrysler) and most of the small independents like Nash and Studebaker as well.

  • Straight-8 If you could make it WHICH YOU CANNOT, this would be typically seen on premium and luxury vehicles, stuff like a Pontiac, Hudson, Kaiser, or Packard. Pretty much the only US automaker to never use a straight-8 design was perhaps surprisingly Ford.

  • V8 was sometimes seen as an optional engine on standard makes and some trucks, usually Fords. Generally, V8s are luxury car engines though which is why the Ford Flathead V8 was such a big deal. You could get a luxury car engine in your cheapo Ford. A V8 in the 40s was de facto for luxury cars.

  • V12 top-of-the-line luxury cars in the 1940s, such as Lincolns did use V12s. These were reserved to their halo models, however.

  • V16 1940 did mark the last year of the famous Cadillac V-16 but if you are going for all-out absurd luxury, there is a historical justification for it and it wouldn’t be far fetched.

And with American V8s you ALWAYS use a crossplane crankshaft! Cadillac were the ones who pioneered this afterall.

Fun fact about V16s: Chrysler was developing a V16 design during World War II for the US military and intended for next-generation ultra-high performance piston engine fighter aircraft. Jets came of age during World War II meaning the design never saw the light of day. Much of the research that went into it however found its way into Chrysler’s post-War V8 designs, one element of which is to this day a marketing gimmick for them – the hemispherical combustion chamber.


Valvetrain tech in the 1940s was still quite primitive. First of all, many if not most of the engines made during this era used sidevalve designs which we cannot build in Automation. We are limited to strictly variations of overhead valves whether its pushrod, overhead cam, or dual overhead cam.

That being said, the pushrod overhead valve design was common, particularly in straight-6 designs. V designs more typically used sidelvalves because it was simpler and many manufacturers stuck to sidevalve designs in general.

If you really want the true 1940s American car engine (the fact that you can’t notwithstanding), one of the ways you can simulate sidevalve designs is by negative quality spam on either pushrod OHV or direct-acting overhead cam. There is an argument to be had either way.

Our good old friend Crosley was the only exception this. They were the first American manufacturer to use an overhead cam, specifically a direct-acting overhead cam, on their engines in 1946.


Displacements of American engines in the 1940s were somewhat more modest compared to the 50s and 60s, capping at about 5.5L in passenger cars and light trucks:

  • Straight-4s had finally gotten away from the absurd displacements of the early years and were usually around 2.0L. The Crosley straight-4 was odd for an American design however at just 750cc.

  • Straight-6s and Straight-8s were typically seen between 3.0L and 5.0L though some examples like the Chrysler Straight-8 did go slightly above to about 5.5L.

  • V8 and V12s were usually between 3.5L and 5.5L. Cadillac V8s did go has high as 5.7L

The Cadillac V16 was somewhat absurd at 7.1L but it was a holdout from the 1930s when such displacements were common.

An important note on bore and stroke: most 1940s American designs were significantly undersquare i.e. having a larger stroke than bore. How significant? Normally at least 10mm and as much as 35 mm larger stroke than bore.

Late 1940s post-War designs are when we start to see the transition to square or oversquare designs.

EDIT: Another note on V8s here. 1948 and 1949 mark the birth of the first generation of the muscle car era V8s. So for a late 1940s V8, it would be acceptable for it to be designed with up to about 7.0L of displacement in mind but still only being about 5.5L in its initial configuration.


Cast iron. Nuff said. The only except that I know of is the Crosley engine which was made of… copper? Yeah Crosley is frickin weird.

Fuel Systems:

All I can say is Ooof.

Most engines were running just one single-barrel carburetor. Some luxury and performance engines would see dual or triple carburetors, particularly if they were long engines like straight-8s or V12s.

AFR? Give up and cry: 13.5ish to 1 or richer.

See my post on carburetor tuning for the full explanation.

But that being said, it doesn’t really matter. 1940s engines were low revving torque monsters. Most of them didn’t go above 4000 RPM and often topped out at about 3500.

Speaking of which lets talk about


Or Kilowatts. Whatever… same thing.

The power that 1940s engines make can be summarized as whatever the engine makes is enough!

Actual power figures from this era are hard to come by and if you do, they are likely obtained by a whole bunch of non-standardized practices. The power figures we do have though are nonetheless not impressive.

This means that its hard to say for certain what kind of power you should expect to make except that whatever you’re modern brain thinks is appropriate probably needs to be knocked down a couple notches. Most engines were only making up to or slightly exceeding 100 hp. For large displacement luxury engines, maybe upwards of 150 hp. Don’t spend your time trying to make big numbers though or even really doing much tuning at all.

That actually feeds nicely into my next point:


Tubular headers were pretty much only seen on race cars!

Everything production used cast logs, or maybe short cast. I would further argue that 1940s engines were so strangled that if you are trying to simulate a sidevalve design say, a cast log exhaust header goes a long way towards doing that.


Virtually all American cars and trucks of the 1940s were RWD. The only real exceptions are some trucks and offroaders like the famous Willys MB “Jeep” and the post-War Jeep truck which were 4x4s.

Also, virtually all American cars used 3-speed manuals. Some trucks and offroaders had 4-speed manuals as an option. The only exceptions that I know of are irrelevant because Automation won’t let you build what they had. I am referring of course to the GM Hydramatic transmission found in Cadillacs and Oldsmobiles.

Yes. GM was making an automatic transmission in 1939. And it had four forward gears! How about that?

Wheels and Tires

Like carburetors, all I can say here is Ooof.

American cars of the 1940s typically used 5 to 7 inch, or 125 to 185 mm, wide tires with between a 90 and 110 profile sidewall. Ouch!


  • Entry level cars
    • 125 - 145 mm tires
    • 14 or 15 inch wheels
  • Standard / large / entry level luxury cars
    • 145 - 165 mm tires
    • 15 or 16 inch wheels
  • Halo luxury / limousine
    • 165 - 185 mm tires
    • 16 inch wheels

Trucks would follow similar guidelines but larger trucks and some offroaders would use as large as 18 inch wheels and stick to the 100-110 profile range because load capacity and such. That oh so famous Willys MB “Jeep” uses a 17 inch wheel for instance.


Oh god WHY?

1940s brake tech was bad, bad, bad, bad, BAD. Of course cars were lighter and much easier to stop. But that doesn’t change the fact that 9, 10, and 11 inch drums brakes are bad. However, asbestos brake shoes were a thing and if you didn’t know, asbestos brake linings give you cancer have excellent stopping power. You could lock wheels if you were really trying.

But just be warned. Shit is bad.

  • How much brake fade are you going to have? All of it.
  • How much stopping power are you going to have? None of it.


What aerodynamics? Don’t be putting wings, lips, or any of that hoopla on your cars though. A few quality points in aero at most.

That being said, Chrysler’s Airstream model was a big deal because it was perhaps the first mass produced American car to be styled with aerodynamics in mind.

Interior and Amenities

Your selection of interior entirely depends on what you want the car to be. But remember this:


You would only see them on halo luxury cars, and then only as an option.

Automotive safety glass was pioneered during this era and was one of the first safety features to be included widely in cars. So especially on late 1940s designs, you should be selecting Standard 40s safety at least.

And to my knowledge, the first cars with power steering don’t show up until the mid 1950s so that is irrelevant.

Suspension Tuning

Well, Automation makes most of your selections for you because, well, there really wasn’t anything else around.

Keep this in mind with 1940s cars – they were still being made with the expectation that they would be going places without paved roads. So as a result, suspension tuning was very soft and mushy and ride heights were large. Spring frequencies typically fell between 1.0 and 1.5 Hz, damping around 0.2 - 0.3 and at this point, I am just going to defer you to my other post on suspension tuning

Because I talk about all of this and more which will be relevant in later eras. The TLDR is alreayd laid out above save for one thing: NEVER BELOW 1.0 HZ! It causes motion sickness.


No no. You don’t get those yet. :smile:

As always, hope this helps! Enjoy.


That’s a nice guide. Never was the type to follow the mechanical realism this closely, and probably will never be the type, but the thoroughness of is stunning, and does give me little bits of inspiration here and there.

That being said,…

There is a little mistake I’ve spotted.


Ooog. Thanks. I get those two mixed up a lot.


Why vans used expensive aluminum panels?


I think that the post should be sticked, no?


The panels thenselves are cheap. The tooling to shape them to complex formats that is expensive. On vans, flat sheets of aluminium were riveted to form the flat sides, top and rear, and flat surfaces from the front, witch is a much cheaper method of fabrication.

This is an ex- post office van that is completely aluminum and has been polished (and lowered, and v8ted, etc)


sway bars were used on a lot of GM full size cars going back to the 50s at least. They were also called stabilizer bars back then. all Buicks built post 1957 have a stabilizer bar in the front and 1959 were offered mid model year in the rear to reduce body roll for example. Many mid body cars like the tri 5 Chevys and muscle era mid bodies probably didnt, but make sure its not called a stabilizer bar which is a sway bar lol

1959 Buick showing the front stabilizer bar in front of the cross member

There is another note to mention. I am a big fan of US full size cars. I am biased, but keeping in mind WHY US automakers used body on frame construction well into the 70s and why trucks still use this design is simple (durability) not just cost. Most big body cars have frames because it adds strength. There are many different designs of frames used over the years on mass production cars, but safety isn’t the main reason why they are hardly used anymore its weight saving and fuel efficiency. Trucks today still use body on frame construction (my 2005 GMC) but they usually score well in crash tests. Trucks don’t have to have the same fuel efficiency standards as cars and they have to be more rugged so they use body on frame design. Yes that tends to mean they are less manageable, but any suspension you can put under a unibody car you can put under a body on frame design. That brings me to a question.

Why isn’t torsion bar suspensions in automation in the 50s? It was used in 55-56 Packards and then in many Chrsyler models and in Citerons? in the same time period. They are a great design although more unreliable then traditional suspension designs.

1956 Packard torsion beam frame



Because more often than not, torsion bars are just a different spring type for an established design, usually double A-arms. Most torsion bar designs I have seen – like those from Chrysler and Packard – usually replace the bushings for one of the A arms with linkages to a longitudinal torsion bar. There are of course exceptions like those in the mid 1970s Dodge Aspen and Plymouth Volare which used a trailing link from a transverse torsion bar mounted just behind the front bumper, but the exceptions are infrequent to the point of being automotive trivia and not much more.

Anyways though, thanks for the history lesson! I knew stabilizer bars were used on some 1960s cars, but its honestly hard to tell which ones. Most of the sources just care about telling you about how big of a V8 they had :smile: .

What I’ve gathered is that low end makes and smaller cars usually omitted them as a cost cutting measure while larger, heavier, higher end designs would sometimes use them on the front as a means of mitigating body roll. American cars were so wide and low to the ground though that body roll really wasn’t as bad as many might think.

And now for something completely different

[queue Monty Python music]

This car is just too cool to let it get lost in an post edit. And it completely blows both my knowledge and expectation of 1940s American cars out of the water.

The Tucker 48

Granted, only 51 of them were built. But lets look at how many traditions this thing blew out of the water with its design:

  • FULLY independent suspension. Yes. Front AND rear. In 1948!
  • Rear engined
  • 6-cylinder horizontal opposed aka BOXER! engine
  • A continuously variable transmission (CVT) was planned, though only 3 cars were equipped
  • Rubber torsion bar suspension

And there was plenty more Preston Tucker, the car’s father, wanted in its design but that was simply too much to do in one car. This list included disc brakes, fuel injection, and tubeless tires which didn’t become industry standard until a decade or so later.

Oh and here is something extra super cool relating to this car:

I got this tip from someone high up in Michigan’s car scene and culture that by pure freak chance I ran into at a Cars and Coffee last weekend. For anyone in Southeast Michigan looking for something to do tomorrow night, there is an exhibit in Royal Oak that will be displaying automotive concept art from all eras of design INCLUDING TUCKER 48 CONCEPT ART!


The center headlight on the Tucker also rotated with the steering.


I love the sheer insanity behind some of Tucker’s engineering decisions, especially the drivetrain. But doing things differently just for the sake of doing stuff differently doesn’t always work. Even the Citroen DS made do with the ancient Traction Avant four cylinder until the very end.


And you forgot the safety glass, padded dashboard, collapsible steering column, reinforced cabin…


Mentioning the Tucker, The owner of the car dealer I purchased my 56 Pontiac from back in 07 had a interesting story to a letter in a picture frame on the wall in his office. Its a official letter from Preston Tucker and I noticed his signature and asked him what the letter was about. He said his dad was a large investor in his company and the letter he sent out to his investors notifying them of the date he would start building his cars and some other information. It was interesting talking to Jeremy about the letter. He remembered his dad telling him about it and that he told Jeremy “Its to bad he got into hot water. It was a great car, and would have been more then a novelty car if he was given just 6 more months to get it off the ground”. The thing about the Tucker is that it wasn’t the first at hardly anything. Boxer, disc brakes, padded dash, safety glass were all on production cars or limited production cars by then. The things the Tucker was exceptional in was being so focused on safety and reasonable cost. The idea was to make the 'Model T Ford of the 50s with focus on safety, reliability, and affordability." I do think the torsion bar suspension, 4 speed automatics, and different frame designs should be at least in a later DLC add on. I personally would love to help in the frame design characteristics (box, K, X, perimeter, etc) as they all have different characteristics that can really effect the durability, safety, and cost of a car. For example a perimeter frame is safer and offers a lower center of gravity, but more expensive and not as durable as x or k frames (Think 1959 Oldsmobile). The K frame is safe, but doesn’t offer floor pans to be dropped below the frame rails. Its cheaper then X frames, but more durable then box frames (think 1959 Buick). X frames are the most durable (which is why most full size convertibles in the 50s and 60s used them), but has a higher center of gravity, but safer then box frames (think 1958 Buick). Box frames offer lower center of gravity, but not durable or safe, but cheap to produce (think 1957 Chevy).


Concerning the 60’s American cars, particularly the off-roaders the Ford Bronco was the first to go to front coils rear leaf in 1966 the rest started to go to front coils in the 80’s, I think the last hold out was the Jeep Wrangler in the late 90’s/early 00’s. Most that did go to coils even then used rear leaf springs, most had solid axles front and rear.


What does the game call Independent “I” Beam suspension?
I can remember Ford commercials from the early seventies going head to head with Chevrolet’s Heavy Duty Coil Spring suspension system.