This is also often referred to as pushing, plowing, or refusing to turn in. The car is referred to as being ‘tight’ because it is stable and far from wanting to spin.

As with oversteer, understeer has a variety of sources such as mechanical traction, aerodynamics and suspension.

Classically, understeer happens when the front tires have a loss of traction during a cornering situation, thus causing the front-end of the vehicle to have less mechanical grip and become unable to follow the trajectory in the corner.

In modern race cars, especially open wheel cars, understeering is caused mainly due to the aerodynamic configuration. In this respect, the lack of a heavy aerodynamic load (downforce) in the front side prevents the front tires from gaining enough traction. At the same time understeer can be caused by having a heavier aerodynamic load at the rear end of the car giving the rear tires more traction than the front tires. Also, suspension balance should take into account the types of surfaces being driven – differing levels of friction in each surface influence the potential understeer behavior. Camber angles, ride height, tire pressure and center of gravity are important factors that determine the understeer/oversteer handling condition.

Understeer covers several different phenomena, in particular, there is a big difference between linear range understeer, typically between 0 and 0.4g, and limit handling understeer, which is at higher lateral accelerations, and is what racing drivers are talking about.

In a rear wheel drive car, increased front toe in (i.e. the fronts of the front wheels are closer together than the backs of the front wheels) provides greater straight-line stability at the cost of some sluggishness of turning response, as well as a little more tire wear as they are now driving a bit sideways. On front wheel drive cars, the situation is more complex.

Toe is always adjustable in production automobiles, even though caster angle and camber angle are often not adjustable. Maintenance of front end alignment, which used to involve all three adjustments, currently involves only setting the toe; in most cases, even for a car in which caster or camber are adjustable, only the toe will need adjustment.

One related concept is that the proper toe for straight line travel of a vehicle will not be correct while turning, since the inside wheel must travel around a smaller radius than the outside wheel; to compensate for this, the steering linkage typically conforms more or less to Ackermann steering geometry, modified to suit the characteristics of the individual vehicle.

It should be noted that individuals who decide to adjust their car’s static ride height, either by raising or lowering, should immediately have the car properly aligned. The goal is to bring total front and rear toe settings to 0°, as toe is the major contributor to abnormally increased rate of tire wear. The common misconception is that Camber angle causes an increased rate of tire wear, when in fact camber’s contribution to tire wear is usually only visible over the entire life of the tire.

Alternatively the rotation of the pinion that is mounted on a locomotive or a railcar will engage the rack between the rails and pull a train along a steep slope.

The rack and pinion arrangement in vehicle steering is commonly found in the steering mechanism of cars or other wheeled, steered vehicles. This arrangement provides a lesser mechanical advantage than other mechanisms such as recirculating ball, but much less backlash and greater feedback, or steering “feel”. The use of a variable rack was invented by Arthur E Bishop, so as to improve vehicle response and steering “feel” on-centre, and that has been fitted to many new vehicles after he created a hot forging process to manufacture the racks, thus eliminating any subsequent need to machine the form of the gear teeth.

The tendency of a car to oversteer is affected by several factors such as mechanical traction, aerodynamics and suspension, and driver control. The driving technique called opposite lock is meant to cope in this circumstance.

Limit oversteer happens when the rear tires exceed the limits of their lateral traction during a cornering situation before the front tires do, thus causing the rear of the vehicle to head towards the outside of the corner. More generally oversteer is the condition when the slip angle of the rear tires exceeds that of the front tires.

Rear wheel drive cars are generally more prone to oversteer, in particular when applying power in a tight corner. This occurs because the rear tires must handle both the lateral cornering force and engine torque.

In modern race cars, especially open-wheel race cars, oversteering in high speed turns is caused mainly by aerodynamic configuration[citation needed]. In this respect, a heavier aerodynamic load on the front of the car relative to the rear causes it to oversteer. Oversteer in low speed turns is often reduced or eliminated electronically through traction control (if the sanctioning body allows their use). Nevertheless, the required front/rear balance to make the cars fast through corners is obtained by setting up the aerodynamics and balancing the suspension. The car’s tendency toward oversteer is generally increased by softening the front suspension or stiffening the rear suspension. Camber angles, ride height, and tire pressures can also be used to tune the balance of the car.

An oversteering car is alternatively referred to as ‘loose’ or ‘tail happy’.

How do you differentiate Oversteer and Understeer?
The racing driver’s joke is “When you see the tree you’re about to hit, it’s called understeer. When you can only hear and feel it, it’s oversteer.” Another is “Oversteer is when the passenger is scared; Understeer is when the driver is scared.” To put things in even simpler terms, when you turn into a corner, oversteer is when the car turns more than you expected and understeer is when it turns less than you expect.

The pivot points of the steering are angled such that a line drawn through them intersects the road surface slightly ahead of the contact point of the wheel. The purpose of this is to provide a degree of self-centering for the steering – the wheel casters around so as to trail behind the axis of steering. This makes a car easier to drive and improves its straight line stability (reducing its tendency to wander). Excessive caster angle will make the steering heavier and less responsive, although, in racing, large caster angles are used to improve camber gain in cornering. Caster angles over 10 degrees with radial tires are common. Power steering is usually necessary to overcome the jacking effect from the high caster angle.

The steering axis (the dotted line in the diagram above) does not have to pass through the center of the wheel, so the caster can be set independently of the mechanical trail, which is the distance between where the steering axis hits the ground, in side view, and the point directly below the axle. The interaction between caster angle and trail is complex, but roughly speaking they both aid steering, caster tends to add damping, while trail adds ‘feel’, and returnability. In the extreme case of the shopping trolley (shopping cart in the US) wheel, the system is undamped but stable, as the wheel oscillates around the ‘correct’ path. The shopping trolley/cart setup has a great deal of trail, but no caster. Complicating this still further is that the lateral forces at the tire do not act at the center of the contact patch, but at a distance behind the nominal contact patch. This distance is called the pneumatic trail and varies with speed, load, steer angle, surface, tire type, tire pressure and time. A good starting point for this is 30 mm behind the nominal contact patch.

Camber angle alters the handling qualities of a particular suspension design; in particular, negative camber improves grip when cornering. This is because it presents the tire, which is taking the greatest proportion of the cornering forces, at a more optimal angle to the road, increasing its contact patch and transmitting the forces through the vertical plane of the tire, rather than through a shear force across it. On the other hand, for maximum straight-line acceleration, obviously the greatest traction will be attained when the camber angle is zero and the tread is flat on the road. Proper management of camber angle is a major factor in suspension design, and must incorporate not only idealized geometric models, but also real-life behavior of the components; flex, distortion, elasticity, etc. What was once an art has now become much more scientific with the use of computers, which can juggle all the variables mathematically instead of relying on the designer’s intuitive feel and experience, and as a result the handling of even low-priced automobiles has improved dramatically in recent years.

In older cars with double wishbone suspensions, camber angle was usually adjustable, but in newer models with McPherson strut suspensions it is normally fixed. While this may reduce maintenance requirements, if the car is lowered by use of shortened springs, this changes the caster angle (as described in McPherson strut) and can lead to increased tire wear and even impaired handling. For this reason, individuals who are serious about modifying their car for better handling will not only lower the body, but also modify the mounting point of the top of the struts to the body to allow some fore/aft movement for caster adjustment. Aftermarket plates with slots for strut mounts instead of just holes are available for most of the commonly modified models of cars.

Another reason for negative camber is that a rubber tire tends to roll on itself while cornering. If the tire had zero camber, the inside edge of the contact patch would begin to lift off of the ground, thereby reducing the contact patch. By applying negative camber, this effect is reduced, thereby maximizing the contact patch.

Positive camber is generally used in vehicles for Off-Road use, such as agricultural tractors. In such vehicles, the positive camber angle helps to achieve a lower steering effort.

Since it came into widespread use in production cars (with “version 2″ in 1978), ABS has made considerable progress. Recent versions not only handle the ABS function itself (i.e. preventing wheel locking) but also traction control, brake assist, and electronic stability control, amongst others. Not only that, but from history at Bosch its version 8.0 system now weighs less than 1.5 kilograms, compared with 6.3 kg of version 2.0 in 1978.

A typical ABS is composed of a central electronic unit, four speed sensors (one for each wheel), and two or more hydraulic valves on the brake circuit. The electronic unit constantly monitors the rotation speed of each wheel. When it senses that any number of wheels are rotating considerably slower than the others (a condition that will bring it to lock) it moves the valves to decrease the pressure on the braking circuit, effectively reducing the braking force on that wheel. Wheel(s) then turn faster and when they turn too fast, the force is reapplied. This process is repeated continuously, and this causes the characteristic pulsing feel through the brake pedal.

The sensors can become contaminated with metallic dust and fail to detect wheel slip; this is not always picked up by the internal ABS controller diagnostic.

One step beyond ABS are modern ESC systems. Here, two more sensors are added to help the system work: these are a wheel angle sensor, and a gyroscopic sensor. The theory of operation is simple: when the gyroscopic sensor detects that the direction taken by the car doesn’t agree with what the wheel sensor says, the ESP software will brake the necessary wheel(s) (up to three with the most sophisticated systems) so that the car goes the way the driver intends. The wheel sensor also helps in the operation of CBC, since this will tell the ABS that wheels on the outside of the curve should brake more than wheels on the inside, and by how much.