Featured Articles

Driving 101: Understeer Versus Oversteer

Posted in driving, General, How To by Kurt Ernst | February 28th, 2010 | 5 Responses |

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.

Our Best Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

5 Responses

  1. DaveMofo says:

    There is no better feeling than sliding a car. That is all :)

  2. Kurt says:

    We’re talking “no better feeling while wearing clothes”, right?

    I can think of one: drifting a car in a corner after a properly rev-matched fouth to third gear downshift.

  3. DaveMofo says:

    Yeah…that would be the winner of “best while clothes are on” kinda feeling.

    I love a good power shift, no clutch, smooth shift (up or down).
    True, my friend! Very true!

  4. Saber says:

    Great video!

  5. Astraist says:

    The description is not scientific/professional. First, understeer is the natural tendency of all cars on earth: Rally cars, professional F-1 race cars, rear wheel drive, front wheel drive and what not. They all understeer because of the laws of physics (Newtons’ first law). Designing any car as neutral or oversteering will reduce overall grip and make the car nearly impossible to drive!

    Oversteer can be caused only after the transient (once the wheel has been turned fully into the corner) and under a certain provocative action of the driver – be it a weight transfer to the front or a sudden application of power to the rear wheels. Under these conditions, to recommend drivers to let go of either the brake or throttle is not accurate. In all situations other than specific extremities, oversteer is recovered from while using the throttle.

    Without throttle, the car is going to dive over it’s front wheels and reduce the ability of the sliding rear wheels to resist the yaw. Too much throttle is going to increase the physical forces (either longitudinal or lateral) working on the car and on the sliding wheels. The proper throttle input depends on many conditions, but the most important one is the drivetrain: A front-wheel drive car can use it’s power for recovery without loading the rear wheels with an acceleration vector. The result is that the need to turn the wheel towards where the back is coming out, is removed and all you have to do is straighten the wheel up while pulling the car forward on throttle.

    In a rear or all-wheel driven car, the proper correction is more like what you described, only that you have to maintain constant throttle: Just enough throttle for the car to maintain a constant speed in which it is not decelerating or accelerating. Without this throttle input the steering correction may become totally inefficient, sub-efficient or over-efficient (throwing you in the other way around).

    To be truly pedantic, oversteer is not defined as “the back end coming loose”, because this can also be attributed to cars with a passive rear steering tendency. The cars develop a certain initial understeer and than the rear suspension applies a toe-out of the outside wheel and the car rotates around the corner in what feels like a momentary oversteer where in fact, the car’s understeer has increased in physical terms.