By on March 20, 2010

March 20, 2010.  Spring Equinox. Spring has sprung. How could Thetruthaboutcars.com celebrate the first day of spring 2010 better than with a concise pictorial history of springs?

Apart from tires and seats (which typically have their own springs, the seats, not the tires) the car’s suspension is what protects your (personal) rear end and spine from the rigors of the road. Apart from shock absorbers (which we’ll celebrate the minute we’ll find an appropriate season for shock absorbers), springs are an essential ingredient of your suspension. Springs come in three basic flavors.

The common leaf spring has been in use in cars and trucks into the mid eighties. From then on, they became an object of derision, except on heavy duty trucks, which use them to this day. The leaf spring was also called “carriage spring,” because it is as old as the horse-drawn carriage. Hence its humorous effect.

To the untrained, a coil spring seems to be the most logical choice. It’s inbred: Most of us have been created with some type of coil spring involved. (See picture left.) To remove or to install a coil spring, you need to be able to operate a coil spring compressor tool. If you don’t know how to operate it, this can have similar effects as a coiled snake. The coil spring is sometimes used in combination with the leaf spring. Or with a shock absorber inside. We’ll get to that later. There are many other coil springs in your car, from valve springs to the spring that pulls your accelerator back – or not.

Then there’s the torsion spring, that strange contraption I learned to hate when I was a young copywriter and they threw me on the Volkswagen account. Die Drehstabfeder or Der Torsionsstab is (so it has been drummed into me) basically a rod that twists along its length. It was popular in the VW Beetle, in the Porsche 356, in the early Barockengel BMW 501/502, in early Porsche 911s, and several Chrysler and GM cars. To this day, I don’t understand why one would twist a poor old rod if there are springs. To this day, they use torsion bars.

From here on, we get into more complex matters, such as coil-over-oil, (or possibly coil-over-gas, but it doesn’t rhyme). It is a combination of a shock absorber and a spring, also known as a McPherson strut. When I was a young copywriter in 1973, this was a big deal. Later, they confused me completely by combining a McPherson strut with a double wishbone suspension. At that point, I turned into a Creative Director and was above such minutiae.

This concludes our TTACesque celebration of the Spring Equinox. May the sun shine bright on you, don’t forget to change the winter tires, and  give your car a good rinse to get the salt out.

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45 Comments on “Thetruthaboutcars.com Celebrates Spring Equinox...”


  • avatar
    isucorvette

    No mention of the transverse leaf spring within the leaf spring section…

  • avatar
    th009

    One advantage of a torsion bar over coil springs (or leaf springs, for that matter) is space utilization — the bars take very little space.

  • avatar
    Stingray

    What you posted as torsion bar is really an anti-roll bar. It works by torsion too, but is not supporting the weight of the car.

    The torsion bars are being used today in the Ford Ranger (the one designed when Tutankamon was alive) in a longitudinal arrangement, the Peugeot 206 (currently 206 plus) in a transverse arrangement, and some other cars.

    The coil spring works by torsion. In each of its wire coils.

    And the tyres can be modeled also like springs.

  • avatar
    Paul Niedermeyer

    Bertel, the Porsche 996 uses coils; the picture you posted is the anti-sway bar.

  • avatar
    Paul Niedermeyer

    Strictly speaking, an anti-sway bar is a form of torsion bar, so you and wiki are off the hook. But practically speaking, no one in the US refers to sway bars as torsion bars, certainly not in the context of vehicle springs. We’ll let it go this time!

  • avatar
    crash sled

    The common leaf spring has been in use in cars and trucks into the mid eighties. From then on, they became an object of derision, except on heavy duty trucks, which use them to this day.

    .

    I think rear leafs are used on all trucks, not just heavy duty, aren’t they? I think my Rangers all had ‘em, and my Tacoma does.

  • avatar
    mfgreen40

    for a short time in the 70s ? the full sized chevy pickup used coils in the rear.

  • avatar
    Juniper

    Many Moons ago, when I was a rookie, a wise chief engineer told me: “everything is a spring, ignore that at your peril”

  • avatar

    used valve springs make good pen holders.

  • avatar
    djn

    Don’t forget Citroen’s nitrogen gas filled spheres

  • avatar
    niky

    @Juniper: unless they break first…

    -

    Torsion bars just don’t get enough loving. They’re ultra-compact, tough, dependable and easy to adjust and replace. I sometimes wish my trucks came with four torsion bars instead of two bars and a pair of wallowy leaf-springs in the rear.

    They were also used in racing, once upon a time. Ultra-compact and ultra-light, they were ideal for difficult packaging on racers. The only problem is that it’s very hard to make them progressive or variable rate, which is why everything uses coil springs, nowadays.

    Of course… most of the best coil-spring equipped road cars still use torsion bars… as anti-roll bars. And a good anti-roll bar set-up can mean the difference between first-class handling and a wallowy Corolla impersonation (note: current Corolla has no anti-roll/ anti-sway bars… delightfully, horribly easy to pitch into roll-induced oversteer).

    We need a follow-up article on suspensions. Pereferably one which highlights the awesome superiority of the torsion-bar equipped beam axle configuration over all others.

    • 0 avatar
      bumpy ii

      Not a full article as such (that’s what Autozine Technical School is for), but Edmunds periodically posts up suspension walkarounds for the vehicles in their test fleet.

    • 0 avatar
      Stingray

      I invite you to go and check the rear axle of a Peugeot 405. Very very compact and clever. It uses 3 transverse mounted torsion bars: 2 for supporting vehicle’s weight and 1 connects the 2 trailing arms.

    • 0 avatar

      Toyota’s website for 2010 Corolla says “Independent MacPherson strut front, torsion beam rear suspension with front and rear stabilizer bars (XRS adds sport strut tower brace)”. Another Toyota secret uncovered… or is it?

    • 0 avatar
      niky

      Lies, all lies, I tell you! Next thing you know, they’ll claim that a Corolla actually has a steering rack attached to the wheel instead of a little computer that decides if you actually want to turn or are just jiggling it for fun.

      They may be there, but they’re too loose to be useful.

  • avatar
    mistrernee

    Do rubber cones count as springs?

  • avatar
    JimothyLite

    “Later, they confused me completely by combining a McPherson strut with a double wishbone suspension. At that point, I turned into a Creative Director and was above such minutiae.”

    Ha! Thanks for the good laugh!

    • 0 avatar
      bumpy ii

      That last picture isn’t a McPherson strut, as the shock body isn’t a suspension member.

    • 0 avatar

      … does that mean I’m dispensed from writing the suspension article? I couldn’t find an appropriate season anyway.

    • 0 avatar
      crash sled

      No, young man, you are not dismissed from completing your assigned suspension article.

      Please submit a draft outline, to include a free body diagram of the basic forces acting upon a typical passenger vehicle, and the basic means by which the OEMs deal with them, including line drawings as necessary, with short narratives describing each, their pluses and minuses.

      For extra credit, you can get into the historical development of those basic means.

      For real extra credit, you can take a whack at rating them all, and tell us who’s doing it the “best”, by class.

    • 0 avatar

      Sorry, I’ll flunk that royally. Could you write it for me?

    • 0 avatar
      crash sled

      No, can’t help you there, Bertel. I’m the rube you’d be trying to educate with that suspension essay. You made a real good start with this post though, maybe one of the other TTAC guys can follow through for us. ;-)

    • 0 avatar
      leeharvey418

      Thank you bumpy and crash. I almost had a stroke when I saw the description of a coilover as a strut. I was formulating my reply in my head when I saw that there were already a bunch of comments on the post, and I figured somebody had to have pointed out the error of Bertel’s ways. You didn’t disappoint.

  • avatar
    obbop

    My 1972 Duster and the 2004 Silverado were/are equipped with torsion bars located at the front of the vehicle.

    I ponder at the type(s) and amount of math required to ascertain how much energy is “absorbed” by a torsion bar in operation and how that energy is measured.

    Calories? Joules? British Thermal Units.

    So many variables and unknown terms and then one can ponder about the front seats whereupon my too-padded buttocks rest atop foam rubber that apparently performs akin to a spring, a variable rate spring, that offers increasing resistance as compression increases, it seems.

    In any measurement, however, it appears that springs are our friends and that taming them as added to the joys of the human experience and that if we take care of our springs they will care for us and assuredly will be truer than any fickle female whose attention is so easily distracted by the most inane minor affairs such as a shiny bauble and whose attentions can be distracted by minutia.

    Three Huzzahs, lads, for our friends the springs.

    There could be no pogo stick without them. Or could there?

    Is there an affordable easily-used substitute for the spring?

    An electro-mechanic device or a wave- or particle-emitter to perform the task?

    Can an ion beam be harnessed to perform in a spring-like manner?

    So many questions with the answers so elusive.

  • avatar

    Chrysler used to brag about its torsion bars in the ’60s.

  • avatar
    obbop

    Was Dorf’s “Twin I-beam” suspension merely a passing fad superseded by superior technology?

    A flash in the pan that was temporarily a marketer’s dream?

    Other?

    • 0 avatar
      trk2

      The Twin I-Beam and Twin Traction Beam (4WD) was a compromise by Ford to provide an independent front suspension without sacrificing the toughness of a solid front axle. It was a successful compromise in that regard, and it was certainly stronger then GM’s independent front suspension design (Dodge remained solid front axle until much later). It worked by essentially having a rigid front axle for each wheel. One end of the ‘i-beam’ held the wheel assembly and the coil spring, the other end was hinged at the opposite side of the vehicle.

      It suffered from being heavy, particularly having a lot of unsprung weight, and alignment problems since the camber angle did not change during suspension travel. The suspension design suffered from ‘jacking’ during high speed emergency maneuvers and Ford moved to a more traditional double control arm front suspension in the 90′s.

  • avatar
    wmba

    A coil spring is a torsion bar. The coils twist as they compress. Elements of Machinery Engineering 101.

    As someone stated above, all structures are springs, since they all deflect under load. Even trees in a wind, which act somewhat like quarter elliptic leaf springs.

    The energy in a compressed spring is equal to one half the product of the spring constant times the deflection from rest squared. The spring constant is measured by seeing how many pounds it takes to compress a certain length, measured in inches or feet. In the US, that is.

    The rest of the world uses the SI version of the meter-kilogram-second system.

    So in the US, spring energy is measured in ft-lbf (the same as torque, which for convenience is written as lbf-ft). In the rest of the world, the energy stored in a spring should be expressed in joules, but rarely is. There’s always some excuse for muddying the waters.

    It all reeks of the basic lack of knowledge of physics endemic in the world. Boring, etc, etc. But just so everyone is clear, we did the experiment on Hooke’s Law of spring deflection (google it) in Grade 12 physics lab when I was in high school, 1962. I found it interesting and eventually became a mechanical engineer, everyone else yawned and promptly forgot it.

  • avatar
    relton

    Air springs are much more common than people think. Almost all heavy duty trucks (tractor trailer size) use air springs, and do a lot of Ford cars, and high end Euro cars. Perps on the way to the slammer usually ride on air springs that are in the rear of the Crown Vic.

    The nitrogen springs of the Citroen are, essentially air springs, since air is about 3/4 nitrogen.

    Even the newer Amtrak passenger cars ride on air springs.

    Anyone who thinks torsion bars are inherently durable has never owned a 1957 Chrysler product. Every single on failed, at least twice, before Chrysler found a fix.

    The torsion bars that hold up the front of my Eldorado are stressed in both torsion and bending, to give them a rising rate. That is, as the lower control arm rotates, the torsion bar is mounted off-center from the center of the arm’s rotation, so it bends as well as twists. I suppose that makes it a leaf spring as well as a torsion bar.

    Bob

  • avatar
    Moparman426W

    Once chrysler got the torsion bars sorted out they were great. They transfer much of the car’s frontal weight rearward, toward the center. The result is better cornering and stopping, with less nosedive.
    And torsion bars last for decades, unlike coil springs which start to sag after about 8-10 years. And if your torsion bars finally do start to sag you can adjust them.

  • avatar
    Nicodemus

    VW Beetle, Morris Minor, Citroen 2CV all used torsion bar suspension. Whatever your aversion to them didn’t seem to stop them selling reasonably well.

    You also seemed to have utterly missed out rubber springs fitted to about 10 million cars.

  • avatar
    thornmark

    Chryslers had torsion quiet ride:
    http://wheels.blogs.nytimes.com/2010/03/20/classic-ad-chrysler-new-yorker/?ref=automobiles
    which gave them superior handling from 1957 on until they were dropped. I remember my 1965 New Yorker could have its front raised or lowered by adjusting them.

    Chrysler later came up with “transverse” torsion bars, which were supposed to retain the torsion bar handling advantage while providing a softer ride. I don’t think that worked out so well.

    My 1984 Honda CR-X had torsion bars up front. None of its competition handled as well.

  • avatar
    cdotson

    The other benefit of torsion bars that enables softer ride and superior handling is that the entire mass of the spring (the bar) is sprung mass (at least as executed by Chrysler in the 60s and more recently in their IFS 4×4 pickups pre-2006). In both leaf and coil springs a portion, typically ~half, of the spring’s mass must be considered unsprung.

    Belleville springs (or Belleville washers) are also used in F1 racing per Wiki. The Wiki page has a good technical writeup about how they’re useful. I’ve also seen them used as Wiki describes in an anti-sway bar’s end links to tune the spring rate along with urethane isolators.

    Elastomeric bumpers or snubbers are also springs. They’re often used to soften the blow of a bottoming suspension or to prevent catastropic crash at the end of a shock absorber’s travel, or just to prevent structural transmission of vibration (tuned as a sort of spring-mass damper with additional visco-elastic damping).

    A coil-over shock isn’t necessarily a “strut.” Struts typically replace both the upright/knuckle and the upper control arm in an independent suspension. A coil-over shock merely runs the coil spring and shock absorber concentrically, often in conjunction with the typical members of SLA suspension (double wishbone), or even with leaf springs.


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