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 . It is commonly judged by how a vehicle performs particularly during cornering , acceleration, and braking as well as on the vehicle's directional stability when moving in steady state condition.
68-644: [REDACTED] Look up handling in Wiktionary, the free dictionary. Handling may refer to: Automobile handling , the turning characteristics of land vehicles Handling of stolen goods , a statutory offence in England and Wales and Northern Ireland People [ edit ] Adam Handling (born 1988), British chef and restaurateur Danny Handling (born 1994), Scottish football player Piers Handling (born 1949), Canadian film executive Topics referred to by
136-758: A jump effectively as well as absorb small bumps along the off-road terrain effectively. The severe handling vice of the TR3B and related cars was caused by running out of suspension travel. 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. In general, softer rubber , higher hysteresis rubber and stiffer cord configurations increase road holding and improve handling. On most types of poor surfaces, large diameter wheels perform better than lower wider wheels. The depth of tread remaining greatly affects aquaplaning (riding over deep water without reaching
204-428: 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 alloy wheels are common due to their weight characteristics which help to reduce unsprung mass. Magnesium alloy wheels are even lighter but corrode easily. Since only the brakes on the driving wheels can easily be inboard,
272-445: A longer car to turn with a given radius. Power steering 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 has begun to be used on road cars (Some WW II reconnaissance vehicles had it). It relieves
340-534: 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 . Understeer Understeer and oversteer are vehicle dynamics terms used to describe
408-399: 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
476-415: A path with a greater radius. The back end will swing out and the vehicle will turn toward the inside of the curve. If the steering angle is not changed, then the front wheels will trace out a smaller and smaller circle while the rear wheels continue to swing around the front of the car. This is what is happening when a car 'spins out'. A car susceptible to being loose is sometimes known as 'tail happy', as in
544-547: A tight-radius (lower speed) corner the angular velocity of the car is high, while in a longer-radius (higher speed) corner the angular velocity 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
612-413: 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 and roll stiffness in front and back to minimise
680-417: A variety of manoueuvres. Several tests can be used to determine understeer gradient: constant radius (repeat tests at different speeds), constant speed (repeat tests with different steering angles), or constant steer (repeat tests at different speeds). Formal descriptions of these three kinds of testing are provided by ISO. Gillespie goes into some detail on two of the measurement methods. Results depend on
748-539: 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
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#1732845526974816-406: Is also a handling characteristic. Ignoring the flexing of other components, a car can be modeled as the sprung weight, carried by the springs, carried by the unsprung weight , carried by the tires, carried by the road. Unsprung weight is more properly regarded as a mass which has its own inherent inertia separate from the rest of the vehicle. When a wheel is pushed upwards by a bump in the road,
884-410: Is best to use race driver's descriptive terms "push (plow) and loose (spin)" for limit behavior so that these concepts are not confused. Tyres transmit lateral (side to side) and longitudinal (front to back) forces to the ground. The total traction force (grip) available to the a tyre is the vector sum of the lateral and longitudinal forces, a function of the normal force and coefficient of friction. If
952-428: Is broken, they are relatively free to swing laterally. Under braking load, more work is typically done by the front brakes. If this forward bias is too great, then the front tyres may lose traction, causing understeer. Understeer gradient is one of the main measures for characterizing steady-state cornering behavior. It is involved in other properties such as characteristic speed (the speed for an understeer vehicle where
1020-402: Is changes to the center of mass which cause tyre saturation and inform limit handling characteristics. If the center of mass is moved forward, the understeer gradient tends to increase due to tyre load sensitivity . When the center of mass is moved rearward, the understeer gradient tends to decrease. The shifting of the center of mass is proportional to acceleration and affected by the height of
1088-448: Is complicated by load transfer , 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
1156-553: Is considered to help handling. At least it simplifies the suspension engineers work. Some cars, such as the Mercedes-Benz 300SL have had high door sills to allow a stiffer frame. Handling is a property of the car, but different characteristics will work well with different drivers. 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. Weather affects handling by changing
1224-591: Is different from Wikidata All article disambiguation pages All disambiguation pages Automobile handling In the automotive industry , handling and braking are the major components of a vehicle's "active" safety. They also affect its ability to perform in auto racing . The maximum lateral acceleration is, along with braking, regarded as a vehicle’s road holding ability. Automobiles driven on public roads whose engineering requirements emphasize handling over comfort and passenger space are called sports cars . The centre of mass height, also known as
1292-427: 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,
1360-506: 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
1428-476: 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 an arc. However, in
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#17328455269741496-409: Is taken to the grip limit of the tyres, where it is no longer possible to increase lateral acceleration, the vehicle will follow a path with a radius larger than intended. Although the vehicle cannot increase lateral acceleration, it is dynamically stable. When an oversteering vehicle is taken to the grip limit of the tyres, it becomes dynamically unstable with a tendency to spin . Although the vehicle
1564-412: 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 ”, and using low gears down steep hills may cause some oversteer. The effect of braking on handling
1632-464: Is the rate of change of the understeer angle with respect to lateral acceleration on a level road for a given steady state operating condition. The vehicle is Understeer if the understeer gradient is positive, Oversteer if the understeer gradient is negative, and Neutral steer if the understeer gradient is zero. Car and motorsport enthusiasts often use the terminology informally in magazines and blogs to describe vehicle response to steering in
1700-481: Is therefore, at least from a sporting point of view, preferable that it can be disabled. 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. The frame may flex with load, especially twisting on bumps. Rigidity
1768-423: Is unstable in open-loop control, a skilled driver can maintain control past the point of instability with countersteering and/or correct use of the throttle or even brakes; this is done purposely in the sport of drifting . If a rear-wheel-drive vehicle has enough power to spin the rear wheels, it can initiate oversteer at any time by sending enough engine power to the wheels that they start spinning. Once traction
1836-494: The Citroën 2CV had inertial dampers on its rear wheel hubs to damp only wheel bounce. Aerodynamic forces are generally proportional to the square of the air speed, therefore car aerodynamics become rapidly more important as speed increases. Like darts, airplanes, 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
1904-449: 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 absorbers 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
1972-401: 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
2040-419: The amount of available traction on a surface. Different tires do best in different weather. Deep water is an exception to the rule that wider tires improve road holding. Cars with relatively soft suspension and with low unsprung weight are least affected by uneven surfaces, while on flat smooth surfaces the stiffer the better. Unexpected water, ice, oil, etc. are hazards. When any wheel leaves contact with
2108-451: The angular inertia tensor 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. Automobile suspensions have many variable characteristics, which are generally different in
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2176-439: The car's centre of mass 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
2244-416: The car's design digitally then "test" that design on the computer. 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 tend to slip sideways. This phenomenon is often explained by use of the circle of forces model. One reason that sports cars are usually rear wheel drive
2312-642: 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 and computational fluid dynamics (CFD) have allowed engineers to optimize
2380-424: The center of mass. When braking, more of the vehicles weight (load) is put on the front tyres and an less on the rear tyres. Conversely, when the vehicle accelerates, the opposite happens, the weight shifts to the rear tires. Similarly, as the center of mass of the load is shifted from one side to the other, the inside or outside tyres traction changes. In extreme cases, the inside or front tyres may completely lift off
2448-399: The centre of gravity height, or CGZ, relative to the track, determines load transfer (related to, but not exactly weight transfer ) from side to side and causes body lean. When tires of a vehicle provide a centripetal force to pull it around a turn, the momentum of the vehicle actuates load transfer in a direction going from the vehicle's current position to a point on a path tangent to
2516-439: The compressive resilience of the tire results in rolling resistance 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
2584-433: 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. Depending on the driver, steering force and transmission of road forces back to the steering wheel and the steering ratio of turns of the steering wheel to turns of the road wheels affect control and awareness. Play—free rotation of
2652-499: 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 (ESC)
2720-449: The front and rear and all of which affect handling. Some of these are: spring rate , damping, straight ahead camber angle , 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 and/or by a solid axle. The Citroën 2CV has interaction between
2788-416: The front and rear suspension. The flexing of the frame interacts with the suspension. 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
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2856-402: The ground, eliminating or reducing the steering input that can be transferred to the ground. While weight distribution and suspension geometry have the greatest effect on measured understeer gradient in a steady-state test, power distribution, brake bias and front-rear weight transfer will also affect which wheels lose traction first in many real-world scenarios. When an understeering vehicle
2924-512: 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
2992-432: 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
3060-415: 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
3128-420: The lateral and longitudinal forces presented at the tyre during operations exceeds the tyre's available traction force then the tyre is said to be saturated and will loose its grip on the ground and start to slip. Push (plow) can be understood as a condition where, while cornering, the front tyres become saturated before the rear and slip first. Since the front tyres cannot provide any additional lateral force and
3196-542: 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 cars , compared to sedans and (especially) SUVs . Some cars have body panels made of lightweight materials partly for this reason. Body lean can also be controlled by
3264-488: The rate of change of the understeer angle. The Understeer Angle is the amount of additional steering (at the road wheels, not the hand wheel) that must be added in any given steady-state maneuver beyond the Ackermann steer angle. The Ackermann Steer Angle is the steer angle at which the vehicle would travel about a curve when there is no lateral acceleration required (at negligibly low speed). The Understeer Gradient (U)
3332-425: The rear tyres can, the front of the vehicle will follow a path of greater radius than the rear and if there are no changes to the steering angle (i.e. the steering wheel stays in the same position), the vehicle's front will slide to the outside of the curve. If the rear tyres become saturated before the front, the front tyres will keep the front of the vehicle on the desired path but the rear tyres will slip and follow
3400-413: The resistance to lateral weight transfer and body lean. The wheelbase 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 , which
3468-681: The resulting over/understeer characteristics. 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 ( h e i g h t 2 + w i d t h 2 ) / 12 {\displaystyle 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 Unless
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#17328455269743536-498: The road surface). Increasing tire pressures reduces their slip angle , 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
3604-417: 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 , so that it responds predictably to
3672-413: The same term [REDACTED] This disambiguation page lists articles associated with the title Handling . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Handling&oldid=1165129398 " Category : Disambiguation pages Hidden categories: Short description
3740-525: The sensitivity of the vehicle to changes in steering angle associated with changes in lateral acceleration. This sensitivity is defined for a level road for a given steady state operating condition by the Society of Automotive Engineers (SAE) in document J670 and by the International Organization for Standardization (ISO) in document 8855. Whether the vehicle is understeer or oversteer depends on
3808-402: 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
3876-444: The springs, anti-roll bars or the roll center heights. In steady-state cornering, front-heavy cars tend to understeer and rear-heavy cars to oversteer (Understeer & Oversteer explained) , all other things being equal. The mid-engine design 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
3944-458: 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
4012-400: The steering wheel before the wheels rotate—is a common problem, especially in older model and worn cars. Another is friction. Rack and pinion 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 —provides some of the self-centering tendency. Precision of
4080-500: The type of test, so simply giving a deg/g value is not sufficient; it is also necessary to indicate the type of procedure used to measure the gradient. Vehicles are inherently nonlinear systems , and it is normal for U to vary over the range of testing. It is possible for a vehicle to show understeer in some conditions and oversteer in others. Therefore, it is necessary to specify the speed and lateral acceleration whenever reporting understeer/oversteer characteristics. Many properties of
4148-438: The understeer/oversteer behavior with the limit behavior of a vehicle. The physics are very different. They have different handling implications and different causes. The former is concerned with tire distortion effects due to slip and camber angles as increasing levels of lateral acceleration are attained. The latter is concerned with the limiting friction case in which either the front or rear wheels become saturated first. It
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#17328455269744216-431: 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; Ride quality 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
4284-454: The vehicle affect the understeer gradient, including tyre cornering stiffness, camber thrust , lateral force compliance steer, self aligning torque , lateral weight transfer , and compliance in the steering system. Weight distribution affects the normal force on each tyre and therefore its grip. These individual contributions can be identified analytically or by measurement in a Bundorf analysis . Great care must be taken to avoid conflating
4352-431: The vehicle is very short, compared to its height or width, these are about equal. Angular inertia determines the rotational inertia 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
4420-427: The vehicle's path. This load transfer presents itself in the form of body lean. In extreme circumstances, the vehicle may roll over . 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
4488-465: The way a dog wags its tail when happy and a common problem is fishtailing . In real-world driving, there are continuous changes in speed, acceleration (vehicle braking or accelerating), steering angle, etc. Those changes are all constantly altering the load distribution of the vehicle, which, along with changes in tyre temperatures and road surface conditions are is constantly changing the maximum traction force available at each tyre. Generally, though, it
4556-406: The wheels and tires, usually the brakes , 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 suspension is completely unsprung. The main factors that improve unsprung weight are a sprung differential (as opposed to live axle ) and inboard brakes . (The De Dion tube suspension operates much as
4624-473: 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. The axle track provides
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