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Automobile handling and vehicle handling are descriptions of the way a wheeled vehicle responds and reacts to the inputs of a driver, as well as how it moves along a track or
road A road is a linear way for the conveyance of traffic that mostly has an improved surface for use by vehicles (motorized and non-motorized) and pedestrians. Unlike streets, the main function of roads is transportation. There are many types of ...
. It is commonly judged by how a vehicle performs particularly during cornering, acceleration, and braking as well as on the vehicle's
directional stability Directional stability is stability of a moving body or vehicle about an axis which is perpendicular to its direction of motion. Stability of a vehicle concerns itself with the tendency of a vehicle to return to its original direction in relation ...
when moving in steady state condition. In the
automotive industry The automotive industry comprises a wide range of company, companies and organizations involved in the design, Business development, development, manufacturing, marketing, and selling of motor vehicles. It is one of the world's largest industry ...
, handling and braking are the major components of a vehicle's "active" safety, as well as its ability to perform in
auto racing Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organise ...
. The maximum lateral acceleration is sometimes discussed separately as "road holding". (This discussion is directed at road vehicles with at least three wheels, but some of it may apply to other ground vehicles). Automobiles driven on public roads whose engineering requirements emphasize handling over comfort and passenger space are named
sports car A sports car is a car designed with an emphasis on dynamic performance, such as handling, acceleration, top speed, the thrill of driving and racing capability. Sports cars originated in Europe in the early 1900s and are currently produced by ...
s.


Factors that affect a car's handling


Weight distribution


Centre of mass height

The
centre of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...
height, also known as the centre of gravity height, or CGZ, relative to the track, determines
load transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
(related to, but not exactly
weight transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
) from side to side and causes body lean. When tires of a vehicle provide a
centripetal force A centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous c ...
to pull it around a turn, the
momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
of the vehicle actuates
load transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
in a direction going from the vehicle's current position to a point on a path
tangent In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points on the curve. More ...
to the vehicle's path. This
load transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
presents itself in the form of body lean. In extreme circumstances, the vehicle may
roll over Rollover or roll over may refer to: Arts and entertainment * ''Rollover'' (film), a 1981 American political thriller *''Roll Over'', a 1992 album by Hound Dog * "Roll Over", a 2006 song by Zico Chain * "Roll Over", a 1989 song by Steven Wayne ...
. Height of the centre of mass relative to the wheelbase determines load transfer between front and rear. The car's momentum acts at its centre of mass to tilt the car forward or backward, respectively during braking and acceleration. Since it is only the downward force that changes and not the location of the centre of mass, the effect on over/under steer is ''opposite'' to that of an actual change in the centre of mass. When a car is braking, the downward load on the front tires increases and that on the rear decreases, with corresponding change in their ability to take sideways load. A lower centre of mass is a principal performance advantage of
sports car A sports car is a car designed with an emphasis on dynamic performance, such as handling, acceleration, top speed, the thrill of driving and racing capability. Sports cars originated in Europe in the early 1900s and are currently produced by ...
s, compared to sedans and (especially)
SUV A sport utility vehicle (SUV) is a car classification that combines elements of road-going passenger cars with features from off-road vehicles, such as raised ground clearance and four-wheel drive. There is no commonly agreed-upon definiti ...
s. Some cars have body panels made of lightweight materials partly for this reason. Body lean can also be controlled by the springs,
anti-roll bar An anti-roll bar (roll bar, anti-sway bar, sway bar, stabilizer bar) is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) whee ...
s or the roll center heights.


Centre of mass

In steady-state cornering, front-heavy cars tend to
understeer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occ ...
and rear-heavy cars to oversteer (Understeer & Oversteer explained), all other things being equal. The
mid-engine design In automotive engineering, a mid-engine layout describes the placement of an automobile engine in front of the rear-wheel axles, but behind the front axle. History The mid-engine, rear-wheel-drive format can be considered the original layout ...
seeks to achieve the ideal center of mass, though front-engine design has the advantage of permitting a more practical engine-passenger-baggage layout. All other parameters being equal, at the hands of an expert driver a neutrally balanced mid-engine car can corner faster, but a FR (front-engined, rear-wheel drive) layout car is easier to drive at the limit. The rearward weight bias preferred by sports and racing cars results from handling effects during the transition from straight-ahead to cornering. During corner entry the front tires, in addition to generating part of the lateral force required to accelerate the car's
centre of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...
into the turn, also generate a torque about the car's vertical axis that starts the car rotating into the turn. However, the lateral force being generated by the rear tires is acting in the opposite torsional sense, trying to rotate the car out of the turn. For this reason, a car with "50/50" weight distribution will understeer on initial corner entry. To avoid this problem, sports and racing cars often have a more rearward weight distribution. In the case of pure racing cars, this is typically between "40/60" and "35/65". This gives the front tires an advantage in overcoming the car's moment of inertia (yaw angular inertia), thus reducing corner-entry understeer. Using wheels and tires of different sizes (proportional to the weight carried by each end) is a lever automakers can use to fine tune the resulting over/understeer characteristics.


Roll angular inertia

This increases the time it takes to settle down and follow the steering. It depends on the (square of the) height and width, and (for a uniform mass distribution) can be approximately calculated by the equation: I=M(height^2+width^2)/12. Greater width, then, though it counteracts center of gravity height, hurts handling by increasing angular inertia. Some high performance cars have light materials in their fenders and roofs partly for this reason


Yaw and pitch angular inertia (polar moment)

Unless the vehicle is very short, compared to its height or width, these are about equal. Angular inertia determines the
rotational inertia The moment of inertia, otherwise known as the mass moment of inertia, angular mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is a quantity that determines the torque needed for a desired angular acceler ...
of an object for a given rate of rotation. The yaw angular inertia tends to keep the direction the car is pointing changing at a constant rate. This makes it slower to swerve or go into a tight curve, and it also makes it slower to turn straight again. The pitch angular inertia detracts from the ability of the suspension to keep front and back tire loadings constant on uneven surfaces and therefore contributes to bump steer. Angular inertia is an integral over the ''square'' of the distance from the center of gravity, so it favors small cars even though the lever arms (wheelbase and track) also increase with scale. (Since cars have reasonable symmetrical shapes, the off-diagonal terms of the angular inertia
tensor In mathematics, a tensor is an algebraic object that describes a multilinear relationship between sets of algebraic objects related to a vector space. Tensors may map between different objects such as vectors, scalars, and even other tenso ...
can usually be ignored.) Mass near the ends of a car can be avoided, without re-designing it to be shorter, by the use of light materials for bumpers and fenders or by deleting them entirely. If most of the weight is in the middle of the car then the vehicle will be easier to spin, and therefore will react quicker to a turn.


Suspension

Automobile
suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspende ...
s have many variable characteristics, which are generally different in the front and rear and all of which affect handling. Some of these are:
spring rate A spring is an elastic object that stores mechanical energy. In everyday use the term often refers to coil springs, but there are many different spring designs. Modern springs are typically manufactured from spring steel, although some non- ...
, damping, straight ahead
camber angle Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering a ...
, camber change with wheel travel, roll center height and the flexibility and vibration modes of the suspension elements. Suspension also affects unsprung weight. Many cars have suspension that connects the wheels on the two sides, either by a
sway bar An anti-roll bar (roll bar, anti-sway bar, sway bar, stabilizer bar) is a part of many automobile suspensions that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It connects opposite (left/right) whee ...
and/or by a solid axle. The
Citroën 2CV The Citroën 2CV (french: link=no, deux chevaux(-vapeur), , lit. "two steam horse(power)s", meaning "two ''taxable'' horsepower") is an air-cooled front-engine, front-wheel-drive, economy family car, introduced at the 1948 Paris Mondial d ...
has interaction between the front and rear suspension. The flexing of the frame interacts with the suspension. (See below.)


Spring rate

The following types of springs are commonly used for automobile suspension, variable rate springs and linear rate springs. When a load is applied to a linear rate spring the spring compresses an amount directly proportional to the load applied. This type of spring is commonly used in road racing applications when ride quality is not a concern. A linear spring will behave the same at all times. This provides predictable handling characteristics during high speed cornering, acceleration and braking. Variable springs have low initial springs rates. The spring rate gradually increases as it is compressed. In simple terms the spring becomes stiffer as it is compressed. The ends of the spring are wound tighter to produce a lower spring rate. When driving this cushions small road imperfections improving ride quality. However once the spring is compressed to a certain point the spring is not wound as tight providing a higher (stiffer) spring rate. This prevents excessive suspension compression and prevents dangerous body roll, which could lead to a roll over. Variable rate springs are used in cars designed for comfort as well as off-road racing vehicles. In off-road racing they allow a vehicle to absorb the violent shock from a jump effectively as well as absorb small bumps along the off-road terrain effectively.


Suspension travel

The severe handling vice of the TR3B and related cars was caused by running out of suspension travel. (See below.) Other vehicles will run out of suspension travel with some combination of bumps and turns, with similarly catastrophic effect. Excessively modified cars also may encounter this problem.


Tires and wheels

In general, softer
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
, higher hysteresis rubber and stiffer cord configurations increase road holding and improve handling. On most types of poor surfaces, large diameter
wheel A wheel is a circular component that is intended to rotate on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction wi ...
s perform better than lower wider wheels. The depth of tread remaining greatly affects
aquaplaning Aquaplaning or hydroplaning by the tires of a road vehicle, aircraft or other wheeled vehicle occurs when a layer of water builds between the wheels of the vehicle and the road surface, leading to a loss of traction that prevents the vehicle fr ...
(riding over deep water without reaching the road surface). Increasing tire pressures reduces their
slip angle In vehicle dynamics, slip angle or sideslip angle is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector v_x and the vector su ...
, but lessening the contact area is detrimental in usual surface conditions and should be used with caution. The amount a tire meets the road is an equation between the weight of the car and the type (and size) of its tire. A 1000 kg car can depress a 185/65/15 tire more than a 215/45/15 tire longitudinally thus having better linear grip and better braking distance not to mention better aquaplaning performance, while the wider tires have better (dry) cornering resistance. The contemporary chemical make-up of tires is dependent of the ambient and road temperatures. Ideally a tire should be soft enough to conform to the road surface (thus having good grip), but be hard enough to last for enough duration (distance) to be economically feasible. It is usually a good idea having different set of summer and winter tires for climates having these temperatures.


Track and wheelbase

The
axle track In automobiles (and other wheeled vehicles which have two wheels on an axle), the axle track is the distance between the hub flanges on an axle. Wheel track, track width or simply track refers to the distance between the centerline of two wheels ...
provides the resistance to lateral weight transfer and body lean. The
wheelbase In both road and rail vehicles, the wheelbase is the horizontal distance between the centers of the front and rear wheels. For road vehicles with more than two axles (e.g. some trucks), the wheelbase is the distance between the steering (front ...
provides resistance to longitudinal weight transfer and to pitch angular inertia, and provides the torque lever arm to rotate the car when swerving. The wheelbase, however, is less important than angular inertia (polar moment) to the vehicle's ability to swerve quickly. The wheelbase contributes to the vehicle's
turning radius The turning diameter of a vehicle is the minimum diameter (or "width") of available space required for that vehicle to make a circular turn (i.e. U-turn). The term thus refers to a theoretical minimal circle in which for example an aeroplane, a ...
, which is also a handling characteristic.


Unsprung weight

Ignoring the flexing of other components, a car can be modeled as the sprung weight, carried by the springs, carried by the
unsprung weight The unsprung mass (colloquially unsprung weight) of a vehicle is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them. This contrasts with the sprung mass (or weight) supported by the ...
, carried by the tires, carried by the road. Unsprung weight is more properly regarded as a
mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different elementar ...
which has its own inherent
inertia Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
separate from the rest of the vehicle. When a wheel is pushed upwards by a bump in the road, the inertia of the wheel will cause it to be carried further upward above the height of the bump. If the force of the push is sufficiently large, the inertia of the wheel will cause the tire to completely lift off the road surface resulting in a loss of traction and control. Similarly when crossing into a sudden ground depression, the inertia of the wheel slows the rate at which it descends. If the wheel inertia is large enough, the wheel may be temporarily separated from the road surface before it has descended back into contact with the road surface. This unsprung weight is cushioned from uneven road surfaces only by the compressive resilience of the tire (and wire wheels if fitted), which aids the wheel in remaining in contact with the road surface when the wheel inertia prevents close-following of the ground surface. However, the compressive resilience of the tire results in
rolling resistance Rolling resistance, sometimes called rolling friction or rolling drag, is the force resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is mainly caused by non-elastic effects; that is, not all the energy nee ...
which requires additional kinetic energy to overcome, and the rolling resistance is expended in the tire as heat due to the flexing of the rubber and steel bands in the sidewalls of the tires. To reduce rolling resistance for improved fuel economy and to avoid overheating and failure of tires at high speed, tires are designed to have limited internal damping. So the "wheel bounce" due to wheel inertia, or resonant motion of the unsprung weight moving up and down on the springiness of the tire, is only poorly damped, mainly by the dampers or
shock absorber A shock absorber or damper is a mechanical or hydraulic device designed to absorb and damp shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typically heat) which is then dissipated. Most sh ...
s of the suspension. For these reasons, high unsprung weight reduces road holding and increases unpredictable changes in direction on rough surfaces (as well as degrading ride comfort and increasing mechanical loads). This unsprung weight includes the wheels and tires, usually the
brake A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...
s, plus some percentage of the suspension, depending on how much of the suspension moves with the body and how much with the wheels; for instance a
solid axle Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structura ...
suspension is completely unsprung. The main factors that improve unsprung weight are a sprung differential (as opposed to
live axle A beam axle, rigid axle or solid axle is a dependent suspension design in which a set of wheels is connected laterally by a single beam or shaft. Beam axles were once commonly used at the rear wheels of a vehicle, but historically they have als ...
) and
inboard brake An inboard brake is an automobile technology wherein the disc brakes are mounted on the chassis of the vehicle, rather than directly on the wheel hubs. Its main advantages are twofold: a reduction in the unsprung weight of the wheel hubs, as thi ...
s. (The
De Dion tube De Dion rear axle A de Dion tube is a form of non-independent automobile suspension. It is a considerable improvement over the swing axle, Hotchkiss drive, or live axle. Because it plays no part in transmitting power to the drive wheels, it is ...
suspension operates much as a live axle does, but represents an improvement because the differential is mounted to the body, thereby reducing the unsprung weight.) Wheel materials and sizes will also have an effect.
Aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
alloy wheels In the automotive industry, alloy wheels are wheels that are made from an alloy of aluminium or magnesium. Alloys are mixtures of a metal and other elements. They generally provide greater strength over pure metals, which are usually much softe ...
are common due to their weight characteristics which help to reduce unsprung mass.
Magnesium alloy wheel In the automotive industry, alloy wheels are wheels that are made from an alloy of aluminium or magnesium. Alloys are mixtures of a metal and other elements. They generally provide greater strength over pure metals, which are usually much softe ...
s are even lighter but corrode easily. Since only the brakes on the driving wheels can easily be inboard, the
Citroën 2CV The Citroën 2CV (french: link=no, deux chevaux(-vapeur), , lit. "two steam horse(power)s", meaning "two ''taxable'' horsepower") is an air-cooled front-engine, front-wheel-drive, economy family car, introduced at the 1948 Paris Mondial d ...
had inertial dampers on its rear wheel hubs to damp only wheel bounce.


Aerodynamics

Aerodynamic Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
forces are generally proportional to the square of the air speed, therefore car aerodynamics become rapidly more important as speed increases. Like darts, aeroplanes, etc., cars can be stabilised by fins and other rear aerodynamic devices. However, in addition to this cars also use downforce or "negative lift" to improve road holding. This is prominent on many types of racing cars, but is also used on most passenger cars to some degree, if only to counteract the tendency for the car to otherwise produce positive lift. In addition to providing increased adhesion, car aerodynamics are frequently designed to compensate for the inherent increase in oversteer as cornering speed increases. When a car corners, it must rotate about its vertical axis as well as translate its
center of mass In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may ...
in an arc. However, in a tight-radius (lower speed) corner the
angular velocity In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ...
of the car is high, while in a longer-radius (higher speed) corner the
angular velocity In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ...
is much lower. Therefore, the front tires have a more difficult time overcoming the car's moment of inertia during corner entry at low speed, and much less difficulty as the cornering speed increases. So the natural tendency of any car is to understeer on entry to low-speed corners and oversteer on entry to high-speed corners. To compensate for this unavoidable effect, car designers often bias the car's handling toward less corner-entry understeer (such as by lowering the front roll center), and add rearward bias to the aerodynamic downforce to compensate in higher-speed corners. The rearward aerodynamic bias may be achieved by an airfoil or "spoiler" mounted near the rear of the car, but a useful effect can also be achieved by careful shaping of the body as a whole, particularly the aft areas. In recent years, aerodynamics have become an area of increasing focus by racing teams as well as car manufacturers. Advanced tools such as
wind tunnels Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...
and
computational fluid dynamics Computational fluid dynamics (CFD) is a branch of fluid mechanics that uses numerical analysis and data structures to analyze and solve problems that involve fluid flows. Computers are used to perform the calculations required to simulate th ...
(CFD) have allowed engineers to optimize the handling characteristics of vehicles. Advanced wind tunnels such as Wind Shear's Full Scale, Rolling Road, Automotive Wind Tunnel recently built in Concord, North Carolina have taken the simulation of on-road conditions to the ultimate level of accuracy and repeatability under very controlled conditions. CFD has similarly been used as a tool to simulate aerodynamic conditions but through the use of extremely advanced computers and software to duplicate the car's design digitally then "test" that design on the computer.


Delivery of power to the wheels and brakes

The coefficient of friction of rubber on the road limits the magnitude of the vector sum of the transverse and longitudinal force. So the driven wheels or those supplying the most
braking A brake is a mechanical device that inhibits motion by absorbing energy from a moving system. It is used for slowing or stopping a moving vehicle, wheel, axle, or to prevent its motion, most often accomplished by means of friction. Background ...
tend to slip sideways. This phenomenon is often explained by use of the
circle of forces The circle of forces, traction circle, friction circle, or friction ellipse is a useful way to think about the dynamic interaction between a vehicle's tire and the road surface. The diagram below shows the tire from above, so that the road surface ...
model. One reason that sports cars are usually rear wheel drive is that power induced oversteer is useful, to a skilled driver, for tight curves. The weight transfer under acceleration has the opposite effect and either may dominate, depending on the conditions. Inducing oversteer by applying power in a front wheel drive car is possible via proper use of "
Left-foot braking Left-foot braking is the technique of using the left foot to operate the brake pedal in an automobile, leaving the right foot dedicated to the throttle pedal. It contrasts with the practice of using the left foot to operate the clutch pedal, leavi ...
." In any case, this is not an important safety issue, because power is not normally used in emergency situations. Using low gears down steep hills may cause some oversteer. The effect of braking on handling is complicated by
load transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
, which is proportional to the (negative) acceleration times the ratio of the center of gravity height to the wheelbase. The difficulty is that the acceleration at the limit of adhesion depends on the road surface, so with the same ratio of front to back braking force, a car will understeer under braking on slick surfaces and oversteer under hard braking on solid surfaces. Most modern cars combat this by varying the distribution of braking in some way. This is important with a high center of gravity, but it is also done on low center of gravity cars, from which a higher level of performance is expected.


Steering

Depending on the driver,
steering Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle. Introduction The most conventional steering arrangement allows a driver to turn the front wheels of a vehicle using ...
force and transmission of road forces back to the steering wheel and the
steering ratio Steering ratio refers to the ratio between the turn of the steering wheel (in degrees) or handlebars and the turn of the wheels (in degrees). The steering ratio is the ratio of the number of degrees of turn of the steering wheel to the number of de ...
of turns of the steering wheel to turns of the road wheels affect control and awareness. Play—free rotation of the steering wheel before the wheels rotate—is a common problem, especially in older model and worn cars. Another is friction.
Rack and pinion A rack and pinion is a type of linear actuator that comprises a circular gear (the '' pinion'') engaging a linear gear (the ''rack''). Together, they convert rotational motion into linear motion. Rotating the pinion causes the rack to be driven ...
steering is generally considered the best type of mechanism for control effectiveness. The linkage also contributes play and friction. Caster—offset of the steering axis from the
contact patch Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is commonly used in the discussion of pneumatic (i.e. pressurized) tires, where the term is used strictly to describe the portion of the tire’s ...
—provides some of the self-centering tendency. Precision of the steering is particularly important on ice or hard packed snow where the slip angle at the limit of adhesion is smaller than on dry roads. The steering effort depends on the downward force on the steering tires and on the radius of the contact patch. So for constant tire pressure, it goes like the 1.5 power of the vehicle's weight. The driver's ability to exert torque on the wheel scales similarly with his size. The wheels must be rotated farther on a longer car to turn with a given radius.
Power steering A power steering is a mechanical device equipped on a motor vehicle that helps drivers steer the vehicle by reducing steering effort needed to turn the steering wheel, making it easier for the vehicle to turn or maneuver at lower speeds. Hydraul ...
reduces the required force at the expense of feel. It is useful, mostly in parking, when the weight of a front-heavy vehicle exceeds about ten or fifteen times the driver's weight, for physically impaired drivers and when there is much friction in the steering mechanism.
Four-wheel steering Steering is a system of components, linkages, and other parts that allows a driver to control the direction of the vehicle. Introduction The most conventional steering arrangement allows a driver to turn the front wheels of a vehicle using ...
has begun to be used on road cars (Some WW II reconnaissance vehicles had it). It relieves the effect of angular inertia by starting the whole car moving before it rotates toward the desired direction. It can also be used, in the other direction, to reduce the turning radius. Some cars will do one or the other, depending on the speed. Steering geometry changes due to bumps in the road may cause the front wheels to steer in different directions together or independent of each other. The steering linkage should be designed to minimize this effect.


Electronic stability control

Electronic stability control (ESC) is a computerized technology that improves the safety of a vehicle's stability by attempting to detect and prevent skids. When ESC detects loss of steering control, the system applies individual brakes to help "steer" the vehicle where the driver wants to go. Braking is automatically applied to individual wheels, such as the outer front wheel to counter oversteer, or the inner rear wheel to counter understeer. The stability control of some cars may not be compatible with some driving techniques, such as power induced over-steer. It is therefore, at least from a sporting point of view, preferable that it can be disabled.


Static alignment of the wheels

Of course things should be the same, left and right, for road cars. Camber affects steering because a tire generates a force towards the side that the top is leaning towards. This is called camber thrust. Additional front negative camber is used to improve the cornering ability of cars with insufficient camber gain.


Rigidity of the frame

The frame may flex with load, especially twisting on bumps. Rigidity is considered to help handling. At least it simplifies the suspension engineers work. Some cars, such as the
Mercedes-Benz 300SL The Mercedes-Benz 300 SL (chassis code W 198) is a two-seat sports car which was produced by Mercedes-Benz as a gullwinged coupe (1954–1957) and roadster (1957–1963).Werner Oswald: ''Mercedes-Benz Personenwagen 1945–1985''. Motorbuch Ve ...
have had high doors to allow a stiffer frame.


Driver handling the car

Handling is a property of the car, but different characteristics will work well with different drivers.


Familiarity

The more experience a person has with a car or type of car the more likely they will be to take full advantage of its handling characteristics under adverse conditions.


Position and support for the driver

Having to withstand "g forces" in his/her arms interferes with a driver's precise steering. In a similar manner, a lack of support for the seating position of the driver may cause them to move around as the car undergoes rapid acceleration (through cornering, taking off or braking). This interferes with precise control inputs, making the car more difficult to control. Being able to reach the controls easily is also an important consideration, especially if a car is being driven hard. In some circumstances, good support may allow a driver to retain some control, even after a minor accident or after the first stage of an accident.


External conditions that affect handling


Weather

Weather affects handling by changing the amount of available traction on a surface. Different
tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
s do best in different weather. Deep water is an exception to the rule that wider tires improve road holding. (See aquaplaning under tires, below.)


Road condition

Cars with relatively soft suspension and with low
unsprung weight The unsprung mass (colloquially unsprung weight) of a vehicle is the mass of the suspension, wheels or tracks (as applicable), and other components directly connected to them. This contrasts with the sprung mass (or weight) supported by the ...
are least affected by uneven surfaces, while on flat smooth surfaces the stiffer the better. Unexpected water, ice, oil, etc. are hazards.


Common handling problems

When any wheel leaves contact with the road there is a change in handling, so the suspension should keep all four (or three) wheels on the road in spite of hard cornering, swerving and bumps in the road. It is very important for handling, as well as other reasons, not to run out of suspension travel and "bottom" or "top". It is usually most desirable to have the car adjusted for a small amount of
understeer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occ ...
, so that it responds predictably to a turn of the steering wheel and the rear wheels have a smaller slip angle than the front wheels. However this may not be achievable for all loading, road and weather conditions, speed ranges, or while turning under acceleration or braking. Ideally, a car should carry passengers and baggage near its center of gravity and have similar tire loading,
camber angle Camber angle is one of the angles made by the wheels of a vehicle; specifically, it is the angle between the vertical axis of a wheel and the vertical axis of the vehicle when viewed from the front or rear. It is used in the design of steering a ...
and roll stiffness in front and back to minimise the variation in handling characteristics. A driver can learn to deal with excessive oversteer or understeer, but not if it varies greatly in a short period of time. The most important common handling failings are; *
Understeer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occu ...
– the front wheels tend to crawl slightly or even slip and drift towards the outside of the turn. The driver can compensate by turning a little more tightly, but road-holding is reduced, the car's behaviour is less predictable and the tires are liable to wear more quickly. *
Oversteer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occu ...
– the rear wheels tend to crawl or slip towards the outside of the turn more than the front. The driver must correct by steering away from the corner, otherwise the car is liable to spin, if pushed to its limit. Oversteer is sometimes useful, to assist in steering, especially if it occurs only when the driver chooses it by applying power. *
Bump steer Bump steer is the term for the tendency of the wheel of a car to steer itself as it moves through the suspension stroke. Bump steer causes a vehicle to turn itself when one wheel hits a bump or falls down into a hole or rut. Excessive bump steer ...
– the effect of irregularity of a road surface on the angle or motion of a car. It may be the result of the kinematic motion of the suspension rising or falling, causing toe-in or toe-out at the loaded wheel, ultimately affecting the yaw angle (heading) of the car. It may also be caused by defective or worn out suspension components. This will always happen under some conditions but depends on suspension, steering linkage, unsprung weight, angular inertia, differential type, frame rigidity, tires and tire pressures. If suspension travel is exhausted the wheel either bottoms or loses contact with the road. As with hard turning on flat roads, it is better if the wheel picks up by the spring reaching its neutral shape, rather than by suddenly contacting a limiting structure of the suspension. *
Body roll Body roll is the axial rotation of a Vehicle, vehicle’s Vehicle frame, body towards the outside of a turn. Body roll occurs because the Compliant mechanism, compliance in Car suspension, vehicle suspension allows the vehicle body, which sits upo ...
– the car leans towards the outside of the curve. This interferes with the driver's control, because they must wait for the car to finish leaning before they can fully judge the effect of his steering change. It also adds to the delay before the car moves in the desired direction. It also slightly changes the weight borne by the tires as described in
weight transfer Weight transfer and load transfer are two expressions used somewhat confusingly to describe two distinct effects: *the change in load borne by different wheels of even perfectly rigid vehicles during acceleration *the change in center of mas ...
. * Excessive load transfer – On any vehicle that is cornering, the outside wheels are more heavily loaded than the inside due to the CG being above the ground. Total weight transfer (sum of front and back), in steady cornering, is determined by the ratio of the height of a car's center of gravity to its
axle track In automobiles (and other wheeled vehicles which have two wheels on an axle), the axle track is the distance between the hub flanges on an axle. Wheel track, track width or simply track refers to the distance between the centerline of two wheels ...
. When the weight transfer equals half the vehicle's loaded weight, it will start to
roll over Rollover or roll over may refer to: Arts and entertainment * ''Rollover'' (film), a 1981 American political thriller *''Roll Over'', a 1992 album by Hound Dog * "Roll Over", a 2006 song by Zico Chain * "Roll Over", a 1989 song by Steven Wayne ...
. This can be avoided by manually or automatically reducing the turn rate, but this causes further reduction in road-holding. * Slow response – sideways acceleration does not start immediately when the steering is turned and may not stop immediately when it is returned to center. This is partly caused by body roll. Other causes include tires with high slip angle, and yaw and roll angular inertia. Roll angular inertia aggravates body roll by delaying it. Soft tires aggravate yaw angular inertia by waiting for the car to reach their slip angle before turning the car.


Compromises

Ride quality Ride quality refers to a vehicle's effectiveness in insulating the occupants from undulations in the road surface (e.g., bumps or corrugations). A vehicle with good ride quality provides a comfort for the driver and passengers. Importance Good r ...
and handling have always been a compromise - technology has over time allowed automakers to combine more of both features in the same vehicle. High levels of comfort are difficult to reconcile with a low center of gravity, body roll resistance, low angular inertia, support for the driver, steering feel and other characteristics that make a car handle well. For ordinary production cars, manufactures err towards deliberate understeer as this is safer for inexperienced or inattentive drivers than is oversteer. Other compromises involve comfort and utility, such as preference for a softer smoother ride or more
seating capacity Seating capacity is the number of people who can be seated in a specific space, in terms of both the physical space available, and limitations set by law. Seating capacity can be used in the description of anything ranging from an automobile that ...
.
Inboard brake An inboard brake is an automobile technology wherein the disc brakes are mounted on the chassis of the vehicle, rather than directly on the wheel hubs. Its main advantages are twofold: a reduction in the unsprung weight of the wheel hubs, as this ...
s improve both handling and comfort but take up space and are harder to cool. Large engines tend to make cars front or rear heavy. Fuel economy, staying cool at high speeds, ride comfort and long wear all tend to conflict with road holding, while wet, dry, deep water and snow road holding are not exactly compatible.
A-arm In automotive suspension, a control arm, also known as an A-arm, is a hinged suspension link between the chassis and the suspension upright or hub that carries the wheel. In simple terms, it governs a wheel's vertical travel, allowing it to move ...
or wishbone front suspension tends to give better handling, because it provides the engineers more freedom to choose the geometry, and more road holding, because the camber is better suited to radial tires, than
MacPherson strut The MacPherson strut is a type of automotive suspension system that uses the top of a telescopic damper as the upper steering pivot. It is widely used in the front suspension of modern vehicles, and is named for American automotive engineer Ear ...
, but it takes more space. The older
Live axle A beam axle, rigid axle or solid axle is a dependent suspension design in which a set of wheels is connected laterally by a single beam or shaft. Beam axles were once commonly used at the rear wheels of a vehicle, but historically they have als ...
rear suspension technology, familiar from the
Ford Model T The Ford Model T is an automobile that was produced by Ford Motor Company from October 1, 1908, to May 26, 1927. It is generally regarded as the first affordable automobile, which made car travel available to middle-class Americans. The relati ...
, is still widely used in most sport utility vehicles and trucks, often for the purposes of durability (and cost). The live axle suspension is still used in some sports cars, like the Ford Mustang (model years before 2015), and is better for drag racing, but generally has problems with grip on bumpy corners, fast corners and stability at high speeds on bumpy straights.


Aftermarket modifications and adjustments

Lowering the center of gravity will always help the handling (as well as reduce the chance of roll-over). This can be done to some extent by using plastic windows (or none) and light roof, hood (bonnet) and trunk (boot) lid materials, by reducing the ground clearance, etc. Increasing the track with "reversed" wheels will have a similar effect, but the wider the car the less spare room it has on the road and the farther it may have to swerve to miss an obstacle. Stiffer springs and/or shocks, both front and rear, will generally improve handling on close to perfect surfaces, while worsening handling on less-than-perfect road conditions by "skipping" the car (and destroying grip), thus making handling the vehicle difficult. Aftermarket performance suspension kits are usually readily available. Lighter (mostly aluminum or magnesium alloy) wheels improve handling as well as ride comfort, by lessening unsprung weight. Moment of inertia can be reduced by using lighter bumpers and wings (fenders), or none at all. Fixing understeer or oversteer conditions is achieved by either an increase or decrease in grip on the front or rear axles. If the front axle has more grip than a similar vehicle with neutral steer characteristics, the vehicle will oversteer. The oversteering vehicle may be "tuned" by hopefully increasing rear axle grip, or alternatively by reducing front axle grip. The opposite is true for an understeering vehicle (rear axle has excess grip, fixed by increasing front grip or reducing rear grip). The following actions will have the tendency to "increase the grip" of an axle. Increasing moment arm distance to cg, reducing lateral load transfer (softening shocks, softening sway bars, increasing track width), increasing tire contact patch size, increasing the longitudinal load transfer to that axle, and decreasing tire pressure.


Cars with unusual handling problems

Certain vehicles can be involved in a disproportionate share of
single-vehicle accident Road traffic collisions generally fall into one of five common types: * Lane departure crashes, which occur when a driver leaves the lane they are in and collide with another vehicle or a roadside object. These include head-on collisions and run- ...
s; their handling characteristics may play a role: * Early Porsche 911s – suffered from treacherous lift off oversteer (where the rear of the car loses grip as the driver lifts off the accelerator); also the inside front wheel leaves the road during hard cornering on dry pavement, causing increasing understeer. The roll bar stiffness at the front is set to compensate for the rear-heaviness and gives neutral handling in ordinary driving. This compensation starts to give out when the wheel lifts. A skilled driver can use the 911's other features to his/her advantage, making the 911 an extremely capable sports car in expert hands. Later 911s have had increasingly sophisticated rear suspensions and larger rear tires, eliminating these problems. * Triumph TR2, and TR3 – began to oversteer more suddenly when their inside rear wheel lifted. *
Volkswagen Beetle The Volkswagen Beetle—officially the Volkswagen Type 1, informally in German (meaning "beetle"), in parts of the English-speaking world the Bug, and known by many other nicknames in other languages—is a two-door, rear-engine economy car, ...
– (original Beetle) senstitivity to crosswinds, due to the lightness of the front of the
rear engine In automobile design, a rear-engine design layout places the engine at the rear of the vehicle. The center of gravity of the engine itself is behind the rear axle. This is not to be confused with the center of gravity of the whole vehicle, as an im ...
car; and poor roll stability due to the
swing axle A swing axle is a simple type of independent (rear wheel) suspension designed and patented by Edmund Rumpler in 1903. This was a revolutionary invention in automotive suspension, allowing driven (powered) wheels to follow uneven road surfaces i ...
suspension. People who drove them hard fitted reversed wheels and bigger rear tires and rims to ameliorate. *
Chevrolet Corvair The Chevrolet Corvair is a compact car manufactured by Chevrolet for model years 1960–1969 in two generations. A response to the Volkswagen Beetle, it remains the only American-designed, mass-produced passenger car with a rear-mounted, air- ...
- poor roll stability due to the
swing axle A swing axle is a simple type of independent (rear wheel) suspension designed and patented by Edmund Rumpler in 1903. This was a revolutionary invention in automotive suspension, allowing driven (powered) wheels to follow uneven road surfaces i ...
rear suspension similar to that used in the Volkswagen Beetle, and cited for dangerous handling in
Ralph Nader Ralph Nader (; born February 27, 1934) is an American political activist, author, lecturer, and attorney noted for his involvement in consumer protection, environmentalism, and government reform causes. The son of Lebanese immigrants to the Un ...
's book
Unsafe at Any Speed ''Unsafe at Any Speed: The Designed-In Dangers of the American Automobile'' is a non-fiction book by consumer advocate Ralph Nader, first published in 1965. Its central theme is that car manufacturers resisted the introduction of safety features ( ...
. These problems were corrected with the redesign of the Corvair for 1965, but sales did not recover from the negative publicity and it was discontinued. * The large, rear-engine
Tatra 87 The Tatra 87 (T87) is a car built by Czechoslovak manufacturer Tatra. It was powered by a rear-mounted 2.9-litre air-cooled 90-degree overhead cam V8 engine that produced 85 horsepower and could drive the car at nearly . It is ranked among the f ...
(known as the '
Czech Czech may refer to: * Anything from or related to the Czech Republic, a country in Europe ** Czech language ** Czechs, the people of the area ** Czech culture ** Czech cuisine * One of three mythical brothers, Lech, Czech, and Rus' Places * Czech, ...
secret weapon') killed so many
Nazi Nazism ( ; german: Nazismus), the common name in English for National Socialism (german: Nationalsozialismus, ), is the far-right totalitarian political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in ...
officers during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
that the German Army eventually forbade its officers from driving the Tatra. * Some 1950s American "full size" cars responded very slowly to steering changes because of their very large angular inertia, softly tuned suspension which made ride quality a priority over cornering, and comfort oriented cross bias tires. ''Auto Motor und Sport'' reported on one of these that they lacked the courage to test it for top speed, probably due to their familiarity with smaller European cars and their unfamiliarity with large American cars. *
Dodge Omni The Dodge Omni (and the nearly identical Plymouth Horizon) is a subcompact car that was produced by Chrysler Corporation from the 1978 to 1990 model years. The first Chrysler model line produced with front-wheel drive, the Omni and Horizon were a ...
and
Plymouth Horizon The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...
– these early American responses to the
Volkswagen Rabbit The Volkswagen Golf () is a compact car/small family car (C-segment) produced by the German automotive manufacturer Volkswagen since 1974, marketed worldwide across eight generations, in various body configurations and under various nameplates ...
were found "unacceptable" in their initial testing by
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founded ...
, due to an observed tendency to display an uncontrollable oscillating yaw from side to side under certain steering inputs. While
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...
's denials of this behaviour were countered by a persistent trickle of independent reports of this behaviour, production of the cars was altered to equip them with both a lighter weight steering wheel and a steering damper, and no further reports of this problem were heard. * The
Suzuki Samurai is a Japanese multinational corporation headquartered in Minami-ku, Hamamatsu, Japan. Suzuki manufactures automobiles, motorcycles, all-terrain vehicles (ATVs), outboard marine engines, wheelchairs and a variety of other small internal com ...
– was similarly reported by ''
Consumer Reports Consumer Reports (CR), formerly Consumers Union (CU), is an American nonprofit consumer organization dedicated to independent product testing, investigative journalism, consumer-oriented research, public education, and consumer advocacy. Founded ...
'' to exhibit a propensity to tipping over onto two wheels, to the point where Consumer Reports claimed they were afraid to continue testing the vehicle without the attachment of outrigger wheels to catch it from completely rolling over. In its first set of tests, the Samurai performed well. R. David Little, Consumers Union's technical director, drove the light SUV through several short, hard turns, designed to simulate an emergency, such as trying to avoid a child running in front of the car. An article published several years later in a Consumer Reports anniversary issue prompted Suzuki to sue. The suit was based on the perception that Consumer Reports rigged the results: "This case is about lying and cheating by Consumers Union for its own financial motives," George F. Ball, Suzuki's managing counsel, said Monday. "They were in debt
n 1988 N, or n, is the fourteenth Letter (alphabet), letter in the Latin alphabet, used in the English alphabet, modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is English alphabet# ...
and they needed a blockbuster story to raise and solicit funds." Entrepreneur Magazine reported that "Suzuki's case centered on a change CU made while testing the vehicle. After the Samurai and other SUVs completed the standard course without threatening to roll over, CU altered the course to make the turns more abrupt. The other vehicles didn't show a problem, but the Samurai tipped up and would have rolled over but for outriggers set up to prevent that outcome" After eight years in court the parties consented to a settlement which did not include monetary damages nor a retraction. Commenting on the settlement, Consumer Union said,"Consumers Union also says in the agreement that it "never intended to imply that the Samurai easily rolls over in routine driving conditions." CU Vice President of Technical Policy further stated: "There is no apology. "We stand fully behind our testing and rating of the Samurai." In a joint press statement Suzuki recognized "CU's stated commitment for objective and unbiased testing and reporting." *
Mercedes-Benz A-Class The Mercedes-Benz A-Class is a subcompact car produced by the German automobile manufacturer Mercedes-Benz as the brand's entry-level vehicle. The first generation (internally coded W168) was introduced in 1997, the second generation (W169) in ...
– a tall car with a high center of gravity; early models showed excessive body roll during sharp swerving manoeuvres and rolled over, most particularly during the Swedish
moose test The evasive manoeuvre test (Swedish: ''Undanmanöverprov''; colloquial: moose test or elk test; Swedish: ''Älgtest'', German: ''Elchtest'') is performed to determine how well a certain vehicle evades a suddenly appearing obstacle. This test has ...
. This was later corrected using
Electronic Stability Control Electronic stability control (ESC), also referred to as electronic stability program (ESP) or dynamic stability control (DSC), is a computerized technology that improves a vehicle's stability by detecting and reducing loss of traction ( skiddi ...
and retrofitted at great expense to earlier cars. *
Ford Explorer The Ford Explorer is a range of SUVs manufactured by Ford Motor Company since the 1991 model year. The first four-door SUV produced by Ford, the Explorer was introduced as a replacement for the two-door Bronco II. Within the current Ford light ...
– a dangerous tendency to blow a rear tire and flip over. Ford had constructed a vehicle with a high center of gravity; between 68 and 74 cm above ground (depending on model). The tendency to roll over on sharp changes in direction is built into the vehicle. Ford attempted to counteract the forces of nature by specifying lower than optimum pressures in the tires in order to induce them to lose traction and slide under sideways forces rather than to grip and force the vehicle to roll over. For reasons that were never entirely clear, tires from one factory tended to blow out when under inflated, these vehicles then rolled over, which led to a spate of well publicized
single-vehicle accident Road traffic collisions generally fall into one of five common types: * Lane departure crashes, which occur when a driver leaves the lane they are in and collide with another vehicle or a roadside object. These include head-on collisions and run- ...
s. :Ford and Firestone, the makers of the tires, pointed fingers at each other, with the final blame being assigned to quality control practices at a Firestone plant which was undergoing a
strike Strike may refer to: People * Strike (surname) Physical confrontation or removal *Strike (attack), attack with an inanimate object or a part of the human body intended to cause harm *Airstrike, military strike by air forces on either a suspected ...
. Tires from a different Firestone plant were not associated with this problem. An internal document dated 1989 states ::''Engineering has recommended use of tire pressures below maximum allowable inflation levels for all UN46 tires. As described previously, the reduced tire pressures increase understeer and reduce maximum cornering capacity (both 'stabilising' influences). This practice has been used routinely in heavy duty pick-up truck and car station wagon applications to assure adequate
understeer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Oversteer is what occurs when a car turns (steers) by more than the amount commanded by the driver. Conversely, understeer is what occ ...
under all loading conditions. Nissan (Pathfinder), Toyota, Chevrolet, and Dodge also reduce tire pressures for selected applications. While we cannot be sure of their reasons, similarities in vehicle loading suggest that maintaining a minimal level of understeer under rear-loaded conditions may be the compelling factor.'' :This contributed to build-up of heat and tire deterioration under sustained high speed use, and eventual failure of the most highly stressed tire. Of course, the possibility that slightly substandard tire construction and slightly higher than average tire stress, neither of which would be problematic in themselves, would in combination result in tire failure is quite likely. The controversy continues without unequivocal conclusions, but it also brought public attention to a generally high incidence of rollover accidents involving SUVs, which the manufacturers continue to address in various ways. A subsequent NHTSA investigation of real world accident data showed that the SUVs in question were no more likely to roll over than any other SUV, after a tread separation. * The Jensen GT (hatchback coupe) – was introduced in attempt to broaden the sales base of the
Jensen Healey The Jensen-Healey is a British two-seater convertible sports car, produced by Jensen Motors Ltd. in West Bromwich, England from 1972 until 1976. Launched in 1972 as a luxurious and convertible sports car, it was positioned in the market betwe ...
, which had up to that time been a roadster or convertible. Its road test report in ''Motor Magazine'' and a very similar one, soon after, in ''
Road & Track ''Road & Track'' (stylized as ''R&T'') is an American automotive enthusiast magazine. It is owned by Hearst Magazines and is published 6 times per year. The editorial offices are located in New York, New York. History ''Road & Track'' (often ab ...
'' concluded that it was no longer fun enough to drive to be worth that much money. They blamed it on minor suspension changes. Much more likely, the change in weight distribution was at fault. The
Jensen Healey The Jensen-Healey is a British two-seater convertible sports car, produced by Jensen Motors Ltd. in West Bromwich, England from 1972 until 1976. Launched in 1972 as a luxurious and convertible sports car, it was positioned in the market betwe ...
was a rather low and wide fairly expensive sports car, but the specifications of its suspension were not particularly impressive, having a solid rear axle. Unlike the AC Ace, with its double transverse leaf rear suspension and aluminium body, the
Jensen Healey The Jensen-Healey is a British two-seater convertible sports car, produced by Jensen Motors Ltd. in West Bromwich, England from 1972 until 1976. Launched in 1972 as a luxurious and convertible sports car, it was positioned in the market betwe ...
could not stand the weight of that high up metal and glass and still earn a premium price for its handling. The changes also included a cast iron exhaust manifold replacing the aluminium one, probably to partly balance the high and far back weight of the top. The factory building was used to build multi-tub truck frames. * The rear engined
Renault Dauphine The Renault Dauphine () is a rear-engine design, rear-engined economy car manufactured by Renault in a single body style – a Three-box styling, three-box, 4-door sedan (car), sedan – as the successor to the Renault 4CV; more than two ...
earned in
Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...
the
sobriquet A sobriquet ( ), or soubriquet, is a nickname, sometimes assumed, but often given by another, that is descriptive. A sobriquet is distinct from a pseudonym, as it is typically a familiar name used in place of a real name, without the need of expla ...
of the ''"widow's car"'', due to its bad handling. * Three-wheeled cars/vehicles have unique handling issues, especially considering whether the single wheel is at the front or back. (Motorcycles with sidecars; another matter.) Buckminster Fuller's
Dymaxion car The streamlined Dymaxion car was designed by American inventor Buckminster Fuller during the Great Depression and featured prominently at Chicago's 1933/1934 World's Fair. Fuller built three experimental prototypes with naval architect Star ...
caused a sensation, but ignorance of the problems of rear-wheel-steering led to a fatal crash that destroyed its reputation.


See also

*
Vehicle dynamics For motorized vehicles, such as automobiles, aircraft, and watercraft, vehicle dynamics is the study of vehicle motion, e.g., how a vehicle's forward movement changes in response to driver inputs, propulsion system outputs, ambient conditions, air ...
*
Auto racing Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organise ...
*
Automotive suspension design Automotive suspension design is an aspect of automotive engineering, concerned with designing the suspension for cars and trucks. Suspension design for other vehicles is similar, though the process may not be as well established. The process en ...
*
Car safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design. ...
*
Downforce Downforce is a downwards lift force created by the aerodynamic features of a vehicle. If the vehicle is a car, the purpose of downforce is to allow the car to travel faster by increasing the vertical force on the tires, thus creating more grip. ...
*
Driving Driving is the controlled operation and movement of a vehicle, including cars, motorcycles, trucks, buses, and bicycles. Permission to drive on public highways is granted based on a set of conditions being met and drivers are required to fol ...
* Grip (autoracing) *
Mechanical engineering Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, and ...
*
Sports car A sports car is a car designed with an emphasis on dynamic performance, such as handling, acceleration, top speed, the thrill of driving and racing capability. Sports cars originated in Europe in the early 1900s and are currently produced by ...


References


External links


Modellers often see the whole picture best.






{{DEFAULTSORT:Automobile Handling Automotive safety Vehicle dynamics