Friday, May 1, 2009

Suspension - Part 1 - A Definition


Since I spent so many years as an engineer in the suspension industry - from off-road trucks to formula cars, and everything in between, I'm going to start by discussing suspension. No surprise, right?

Suspension – What it is and What it Does

Webster’s Dictionary defines suspension as: "n. Act of suspending; intermission; abeyance; deprivation of office or privileges for a time. " In regards to your car, about the only thing in that definition you can apply is the “act of suspending”. The definition of suspend is: "vt. To hang; to cause to cease for a time; to debar temporarily; to stay." Again, applied to your car, only the “to hang” section seems to fit. It seems, then, that the definition of suspension in automotive terms is “the act of hanging.” This slightly twisted definition is actually reasonably accurate, if you ask me, because, in my mind, suspension is what you use to hang the wheels on your car. It would also be accurate to state that suspension is used to hang the car on your wheels. While these last two statements seem to say the same thing a little differently, they actually have individual significance when looked at by themselves, and at some point in the future, I’ll explain why, but for now go ahead and file that bit of information in your gray matter somewhere.

So how do I define suspension? My definition is actually quite simple. Suspension is all the things that connect your car’s chassis to the wheels. Shock absorbers (more correctly called dampers), McPherson struts, coil springs, leaf springs, torsion bars, control arms, radius rods, spindles, knuckles, bushings, ball joints – the list is almost endless. I tend to lump everything into my definition, and then weed out what I don’t need at the moment. Even things like brakes and steering components might fit, depending on what I’m looking at. In some cases, I might even consider the tires and wheels part of the suspension, so my definition might actually be “all the things that ‘connect’ your car’s chassis to the ground.” (Hey, it’s my definition, and it may be a little vague, but I’m stickin’ with it!)

So now that we know what it is, or at least how I define it, we can talk about what it does. I use two favorite words to describe what suspension does – handling and ride. In my book, handling is the most important function that the suspension has. Simply defined, handling is keeping the tires in contact with the ground. If the tires don’t have good, consistent contact, your car won’t accelerate, turn, or stop very well. On a smooth, straight road, the job is pretty simple. On a bumpy, twisting road, it can be a difficult task. The other job that the suspension has, ride, is the isolation of the chassis (including the driver, passengers, and cargo) from road inputs – by road inputs I mean anything that the tires may encounter - like bumps, dips, rocks, roadkill, etc… Both ride and handling have characteristics that can be measured, but ride is a more subjective thing. Some people may think your car rides too firmly to be comfortable, while some may think it’s too soft. Ride and handling are also usually related. Although not always the case, a car that rides more firmly usually handles better than the same car that has a softer suspension. The exception to this rule is usually at the extremes – a car that is too stiff will handle poorly, and a car that is too soft will ride poorly, in the sense that it makes you uncomfortable.
For selected reading on this subject, see my recommended titles at Amazon.com by clicking HERE. I especially recommend the books by my friend Don Alexander.

For those who can't wait, here's a little more: http://hubpages.com/_suspension/hub/HiPerfAutoTech

Stay tuned for more...

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