I once heard an engineering professor spend 10 minutes attempting to explain how anti-roll bars work. He was trying to answer a student’s question that was itself as perplexing as the instructor’s response.
The professor was no doubt a very bright guy, thoroughly trained in the theory of suspension design, but he was speaking without using a single word legal in even the friendliest game of Scrabble. 
His audience consisted mainly of engineering school graduates, some of whom were already working in the automotive industry. All very smart folks, but few had much practical, hands-on knowledge or experience. I’m certain some of the younger ones – especially the females (no offense intended) had never seen an anti-roll bar.
By the time the prof had finished, everyone was thoroughly confused. That included me and, probably, the professor.
I was likely the dumbest and certainly the least educated guy in the room, but I have spent many hours fiddling with anti-roll bars (some call them “sway bars”) and other suspension components on both race and street cars. Plus, I have pretty much read every book and viewed every instructional video available on race car suspension.
So I asked the person who’d posed the original question: “Did you mean to ask, ‘Explain what happens when you fit a stronger-rate bar?’”
“Yes,” he said. To which I responded: “A stronger bar reduces grip on that end of the car. Tightening the front increases push. Tightening the rear bar makes it looser.”
It was exactly what he wanted to know. I could see light bulbs going on all across the room, but that may have just been people waking up because the professor had stopped speaking. If you need to know more on anti-roll bars, start reading books on race car suspension adjustment and design. Racers don’t care a bit about theory; they just want to go fast, right now.
My points: Whether the group is engineering school grads, those who work in the automotive industry, racers or even car writers, the knowledge bar is often a lot lower than many think. A simple answer may be all that’s needed to satisfy inquiring minds. Heck, it may be all that the particular audience can understand.
A couple of paragraphs ago, I just threw around a couple of terms – “push” and “loose” – that far from every reader fully understands. You probably do, so good on you. But for the others…These are terms oval track drivers use to describe what happens when the car reaches the limit of tire grip. Those points are best understood right in the middle of a turn, but “push” and “loose” are not physical sensations exclusive to turns.
When you’re driving as fast as possible (or hit an icy patch on a freeway transition ramp), one end of the car inevitably loses grip before the other. If that’s the front tires, the car is pushing (or “tight”). If it’s the rear tires, it’s loose.
Think of it this way: With “push” you hit the wall with the front bumper, with “loose” you hit wall with the rear bumper. Stock car drivers use another term: “free.” This means the fronts and rears are sliding at about the same rate…it’s really fast, but it’s hard racing it that way.
Rather than “push,” “loose” and “free,” tire and auto engineers and road racers use “understeer,” “oversteer,” and “neutral” to describe the same things. Unless the information gets muddled.
Side note: On a recent broadcast, famed NASCAR driver and current TV announcer Darrell Waltrip – I hope in jest – got the terms reversed. Back in the 1970s, a champion Can-Am road racer got the terms reversed, so his team set the car up to counter what he said, with the expected results.
Beyond Definitions
Right now, many of you are like another engineer I met recently. He fully understood the meaning of understeer and oversteer. In fact, part of his job was producing three-dimensional graphs showing what all four tires on a race car were doing at any one moment in time, but he didn’t know what it felt like to have a car push or go loose.
He was like a blind person who could provide a basic description of the Mona Lisa, but didn’t have a feel for the depth of the work.
Push/understeer feels like the steering column has suddenly transformed into rubber. You’ve got the wheel cranked left, but the car isn’t turning nearly as much as you’d like – if at all. In severe cases, it feels as if the steering wheel has snapped off. No matter how much you turn the wheel, the car goes straight. Vehicle speed and mass have overcome the forces of grip (friction), and no amount of steering input will work until speed is sharply reduced. Basically, for the typical driver, push doesn’t end well.
Loose/oversteer, to most highway drivers, feels much like hitting a tree or running into a ditch, because that’s what their car ends up doing when it goes loose. A race driver battling a loose car feels what the outside rear tire is doing. Before the rear end steps out there’s a lightness or, sometimes, shuddering in the outside rear tire. That’s the tire saying, “Whoa, that’s about all I can take!”
It can be likened to an airplane wing as it begins to stall. There’s also a lightness felt through the steering wheel and a change in yaw rate felt through your butt. The rear pitches around quickly and almost without warning, and, depending on speed and road conditions, induces a seemingly endless spin or, at minimum, a sideways trip into an immovable object. Again, for the typical driver, loose doesn’t end well, either.
Neutral, as the name implies, is stable and true. Boring, but fast. The typical driver won’t even notice, which is the best thing.
Don’t feel inferior if you don’t know all the terms bandied about by car writers, broadcasters and professors. They may not fully understand them, either.
The important thing is that you can explain them to your customers. And understand the dynamics as you recommend the right tire for the application.
