Understeer and oversteer.

The two definitions

Driver61 defines understeer (often called "push") as the car turning less than the steering asks because the front tires lose grip first, and oversteer as the rear tires losing traction so the car rotates more than you intended. Virtual Racing School (David Williams, 2016) frames the same idea in terms of grip: understeer is front grip lower than rear grip, and oversteer is rear grip lower than front.

Neither is simply bad. Virtual Racing School says a neutral car, one equally likely to understeer or oversteer when pushed past the limit, is usually the fastest. Adam Brouillard of Paradigm Shift describes the ideal as running near the understeer limit on corner entry and near the oversteer limit on exit, while staying as close to neutral as possible.

The link to weight transfer is direct. Blayze coach Dion von Moltke's rule is that grip follows weight: accelerating moves weight and grip to the rear, braking moves it to the front. Brian Beckman draws the consequence: braking can bring on oversteer, and accelerating can bring on understeer.

What causes each

Driver61's lists of causes, arranged by where in the corner they happen:

Driver61 calls lift-off oversteer snappy and says it is usually a sign the driver was not looking far enough ahead (see vision). NASA Speed News columnist Bryan Van Noy adds that coming off the brake too much, too soon on entry can cause understeer.

Drivetrain layout matters too. Von Moltke says front-wheel-drive cars suffer most from exit understeer and overheated front tires, all-wheel-drive cars also tend to understeer on exit, and rear-wheel-drive cars are more prone to exit oversteer.

Understeer: what the coaches say

Driver61 says the steering goes lighter as the front tires start to slide. Its key point is that adding more steering lock does not help, because the tires are already past their limit. Virtual Racing School calls adding lock the common mistake that usually makes understeer worse, and von Moltke says the same thing from a different angle: once the car is understeering, more steering adds no turning, only tire heat and wear, and it can set up snap oversteer on the exit.

On preventing it, the sources point to the pedals rather than the wheel:

• Entry. Von Moltke says light trail braking toward the apex generally prevents entry understeer (see braking).
• Exit. Driver61 says exit understeer is the most common kind and that the main remedy is patience with the throttle: rotate the car first, then add power smoothly. Von Moltke gives a check: if you cannot begin to unwind the steering as you apply throttle, the throttle came too early.
• Mid-corner. Driver61 describes a brief, deliberate lift in slow hairpins to shift weight forward and help the car rotate.
• Grip on the wheel. Driver61 recommends a relaxed grip for better feel, and lists holding the wheel too tightly among the common understeer mistakes.

Virtual Racing School's suggested response to understeer is to reduce throttle first and then, if needed, brake gently.

Oversteer: what the coaches say

Driver61's correction principles are opposite lock (countersteering) to stop the car rotating further, less entry speed, bleeding off brake pressure during turn-in, and smooth inputs, which it says make any slide more progressive. Its advice on throttle is that the first application out of a corner should be smooth and progressive, to avoid power oversteer.

Virtual Racing School describes two ways drivers make oversteer worse:

• Overcorrecting. Unwinding the countersteer too late, which can pitch the car into a spin the other way.
• Snap oversteer. A sudden switch from understeer to oversteer, made worse if the driver has already piled on steering during the understeer.

Virtual Racing School also presents drifting, or holding the car in oversteer, as a way to build car control rather than a fast way around a track.

How schools teach it

According to a sponsored Motor Sport article, Skip Barber Racing School's one-day course includes skid pan car control, and Skip Barber's own site says its basic high-performance program uses skid pad exercises. The schools and HPDE programs on the technique landing page explain how instruction is structured.

Setup is not the first answer

Both of Driver61's pages list setup among the causes, and both advise beginners not to make setup changes without experience. Its suggestion is to work with an engineer or a professional to establish a base setup. Steering and hand position are covered on seating and hands.