Driving 101: Understeer Versus Oversteer

Writing a “How to Drive” series is like trying to write a “How to Skydive” series. What sounds easy (jump out of the plane, count to ten and open your parachute) is really quite difficult. Many of the things I could teach you about driving require practice under the eyes of a trained instructor. You cannot learn threshold braking simply by reading about it; likewise, if you aren’t doing it properly, all the practice in the world will do you no good. Also, I can’t give specific advice unless I know what you’re driving and what your expectations are; therefore, I’ll need to make this as generic as possible.

With these points in mind, the sole purpose of this ongoing series is to answer some questions about driving that you may not even know you have. I’ll try to make it an enjoyable read, and there will not be a quiz afterward. I’ve got to give you the standard disclaimer as well – driving is dangerous, and while my goal is to make it slightly less so I can’t guarantee this. Read on and drive at your own risk.

Understeer

Understeer, or “push” in racing lingo, refers to the tendency of a vehicle to continue in a straight line when the wheels are turned. Understeer is the natural handling characteristic of front wheel drive and most AWD cars, for several reasons:

• The majority of vehicle weight is carried over the front wheels
• The front wheels must drive the car, brake and steer

Vehicle engineers consider understeer more “recoverable” than oversteer. Drivers with experience behind the wheel prefer their vehicles more neutral. So how do you turn your front wheel drive, understeering pig of a vehicle into a more neutral, better balanced car? Here are a few pointers:

• Tires. Most OEM tires suck monkey ass, and are on the vehicle because one of the major manufacturers bid lower than the others. Scrap your stock tires and spring for something a little stickier. Tire pressure is also critical here. RTFM when it comes to your correct tire pressure, then add two or three pounds to the front and rear. On a front wheel drive car, the fronts should carry at least two pounds more air than the rears.

• Shocks or struts. These things don’t last forever, people. In fact, it’s not uncommon for struts to wear out in as little as 30k miles. If your struts are weak, NOTHING you do will improve handling. Go for a premium aftermarket brand like Koni, KYB or Bilstein.

• Sway bars. Generally speaking, the stiffer the rear sway bar, the less the car will understeer. Unless you’re building a track car, don’t waste your money on “adjustable” sway bars because chances are you’ll just set ‘em and forget ‘em. Solid sway bar ends (as opposed to the stock, rubber mounted ones) also help firm things up noticeably.

• Suspension Bushings. As long as comfort isn’t a concern, consider changing your stock (rubber) bushings to polyurethane ones. Prepare to lose fillings regularly if you do, but isn’t that a small price to pay for better handling?

So, what do you do when you turn into a corner and your car keeps going straight? Simple. Do less of whatever you’re doing – turn less, brake less, accelerate less, etc., and the car will eventually regain traction. Don’t forget that understeer takes some room to correct; as much as you may like Ken Block, don’t practice this where the runoff area includes trees, OK? ?

Oversteer

Those of us who are old enough to have owned rear wheel drive cars as our first rides are WELL acquainted with oversteer. For those of you weaned on VW Golfs and Honda Civics, oversteer may not be familiar to you.

Oversteer (or “loose” in racing terms) refers to the back end of a car coming loose, usually quite suddenly. If corrected poorly, oversteer will most likely result in a spin.

In rear wheel drive cars, oversteer is generally caused by a lack of traction at the rear, coupled by a turn of the front wheels or uneven application of power to the rear wheels. Many things can cause oversteer, but slippery conditions, jerky steering wheel movements and inappropriate braking are usually the root cause.

Mind you, even front wheel drive cars can oversteer. Example? Sure – when first learning how to race cars, yours truly rented a Mitsubishi Eclipse from a local agency. Fast forward to the track day; I’m ten laps or so into this track, have the corners down pretty well and am building up my speed. Down the back straight, past my braking marker (“No problem,” says I, “it’s a front wheel drive car. I’ll just brake harder and take a later apex”). I’m hard on the brakes as I turn in; suddenly, my world is a blur and I feel like an astronaut in lateral G training. I’ve got one complete rotation in and I’m working on my second, when I realize that I’m not going to save this. Key point here: In a spin, both feet in (depress the clutch to the floor and depress the brakes as hard as you can if you know you’re not going to recover a spin). Since the car was an automatic, it was one foot in, but you get the point. OK, So I’m not gonna save it – lock the brakes and slide to the outside of the corner (away from traffic). Other lesson learned? When renting cars for track days, ALWAYS take the LDW insurance.

Anyway, now that you know about Mr. Oversteer, what do you do when he pays you a visit? As with understeer, slightly less of what you’re doing. Gently release some pressure from the brake or gas pedal, whichever your foot is on. Sudden, abrupt movements are very, very bad here. Now, steer the wheel (smoothly) in the direction that the back end is coming around. Feel that? That’s the rear of the car regaining traction. Congratulations! You’ve just caught your first slide.

For practice on catching slides, go to a deserted dirt or snow packed parking lot. In a straight line, accelerate to 20 mph or so. Now, turn the wheel hard left or hard right. What happens? You plow straight: this is understeer. Next, do the same thing, but turn the wheel and pull up the handbrake at the same time – this, my friends is oversteer. Practice catching slides until you get proficient at it, and you’ll learn to love oversteer too.