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A wheelspin occurs when the force delivered to the tire tread exceeds that of available tread-to-surface friction and one or more tires lose traction. This leads the wheels to "spin" and causes the driver to lose control over the tires that no longer have grip on the road surface. Wheelspin can also be done intentionally such as in drifting or doing a burnout. [1]
Standard differentials (also referred to as "open" differentials) always apply equal torque to each wheel. In low traction situations, the total torque delivered to each wheel is limited to the torque that is required to make the wheel with the least traction slip.
During a turn, the weight of the vehicle shifts away from the inner radius and to the outer radius, therefore the inner drive-wheel will often lose traction on hard cornering, and especially when accelerating through a curve.[ citation needed ] Locking differentials and limited slip differentials modify the manner in which torque is distributed to the wheels to reduce wheelspin and improve traction in situations where it is limited. [2]
Wheels can also lose traction when surface conditions reduce available traction such as on snow and ice. As an open differential delivers only enough torque to cause the "weakest" wheel to spin, if one drive wheel is stationary on a low traction surface (mud, ice, etc.), the deliverable torque is limited to the traction available on it.
Oversteer is typically the result of wheelspin, causing the vehicle to lose traction and turn too sharp through a turn. Oversteer can be caused in two different ways, power oversteer and lift-off oversteer. [3] Oversteer can be performed either intentionally or accidentally through these two methods and if the driver doesn't know what they are doing then it could result in an accident. Oversteer is a common trait of rear-wheel drive cars and can also occur in all-wheel drive cars. It can be performed in front-wheel drive cars as well, but it is not as common as they tend to understeer.
Power oversteer is the process of applying power through the throttle pedal while turning to break the traction forces on the driving wheels. Doing this causes the vehicle to slide, and is also known as a powerslide, and the vehicles movement is primarily based on the non-driving wheels (usually the steering wheels).
Wheelspin can also occur when changing gears while the vehicle is in motion, as the inertia of the engine and flywheel rotating at a higher rate than the next highest gear tries to bring the input shaft of the transmission to the same speed. This is known commonly as lift-off oversteer.
Understeer is also a result of wheelspin and traction loss. It results in a vehicle not being able to turn enough when driving through a curve and causes the vehicle to continue forwards instead of turning in the curve. It is caused by using too much power into a turn causing the tires to slide sideways into the curve, preventing the vehicle from turning. Understeer is the easiest form of wheelspin to correct and can usually be done by lifting off of the throttle.
In railway engineering, the term wheelslip is used as a synonym for wheelspin.
Traction control is an electronic system installed in most modern automobiles since 1985. It monitors individual wheel speeds through the Anti-lock Brake System (ABS) or wheel speed sensors and controls engine inputs to maintain stability and traction to the vehicles wheels. When the traction control system notices wheelspin on any of the wheels it limits the fuel provided through the onboard engine management system and controls the speed of the vehicle to prevent excessive wheelspin. [4]
There are several driving techniques that you can follow to prevent wheelspin: [5] [6]
An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type of axle is referred to as a spindle.
A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analog computers.
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, leaving the right foot to share the duties of controlling both brake and gas pedals.
A traction control system (TCS), is typically a secondary function of the electronic stability control (ESC) on production motor vehicles, designed to prevent loss of traction of the driven road wheels. TCS is activated when throttle input and engine power and torque transfer are mismatched to the road surface conditions.
A four-wheel drive, also called 4×4 or 4WD, is a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges.
A limited-slip differential (LSD) is a type of differential gear train that allows its two output shafts to rotate at different speeds but limits the maximum difference between the two shafts. Limited-slip differentials are often known by the generic trademark Positraction, a brand name owned by General Motors and originally used for its Chevrolet branded vehicles.
Quattro is the trademark used by the automotive brand Audi to indicate that all-wheel drive (AWD) technologies or systems are used on specific models of its automobiles.
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. Numerous factors affect handling
A locking differential is a mechanical component, commonly used in vehicles, designed to overcome the chief limitation of a standard open differential by essentially "locking" both wheels on an axle together as if on a common shaft. This forces both wheels to turn in unison, regardless of the traction available to either wheel individually.
ATTESA is a four-wheel drive system used in some automobiles produced by the Japanese automaker Nissan, including some models under its luxury marque Infiniti.
Lift-off oversteer is a form of sudden oversteer. While cornering, a driver who closes the throttle, usually at a high speed, can cause such sudden deceleration that the vertical load on the tires shifts from rear to front, in a process called load transfer. This decrease in vertical load on the rear tires in turn decreases their traction by lowering their lateral force, making the vehicle steer more tightly into the turn. In other words, easing off the accelerator in a fast turn can cause a car's rear tires to loosen their grip so much that the driver loses control and drifts outwards, even leaving the road tailfirst.
Super Handling-All Wheel Drive (SH-AWD) is a full-time, fully automatic, all-wheel drive traction and handling system, which combines front-rear torque distribution control with independently regulated torque distribution to the left and right rear wheels. This way the system freely distributes the optimum amount of torque to all four wheels according to the driving conditions. The system was announced in April 2004, and was introduced in the North American market in the second generation 2005 model year Acura RL, and in Japan as the fourth generation Honda Legend.
ControlTrac four-wheel drive is the brand name of a selectable automatic full-time four-wheel drive system offered by Ford Motor Company. The four-wheel drive system was designed and developed at BorgWarner under its TorqTransfer Systems division in the mid 1980s. BorgWarner calls the system Torque-On-Demand (TOD). ControlTrac was the first automatic system to use software control and no planetary or bevel geared center differential. Instead of a planetary or bevel geared center differential, the system uses a variable intelligent locking center multi-disc differential.
Bump steer is the term for the tendency of the wheel of a car to steer itself as it moves through the suspension stroke.
S-AWC is the brand name of an advanced full-time four-wheel drive system developed by Mitsubishi Motors. The technology, specifically developed for the new 2007 Lancer Evolution, the 2010 Outlander, the 2014 Outlander, the Outlander PHEV and the Eclipse Cross have an advanced version of Mitsubishi's AWC system. Mitsubishi Motors first exhibited S-AWC integration control technology in the Concept-X model at the 39th Tokyo Motor Show in 2005. According to Mitsubishi, "the ultimate embodiment of the company's AWC philosophy is the S-AWC system, a 4WD-based integrated vehicle dynamics control system".
All Wheel Control (AWC) is the brand name of a four-wheel drive (4WD) system developed by Mitsubishi Motors. The system was first incorporated in the 2001 Lancer Evolution VII. Subsequent developments have led to S-AWC (Super All Wheel Control), developed specifically for the new 2007 Lancer Evolution. The system is referred by the company as its unique 4-wheel drive technology umbrella, cultivated through its motor sports activities and long history in rallying spanning almost half a century.
In automotive design, an M4, or Mid-engine, Four-wheel-drive layout places the internal combustion engine in the middle of the vehicle, between both axles and drives all four road wheels.
Torque vectoring is a technology employed in automobile differentials that has the ability to vary the torque to each half-shaft with an electronic system; or in rail vehicles which achieve the same using individually motored wheels. This method of power transfer has recently become popular in all-wheel drive vehicles. Some newer front-wheel drive vehicles also have a basic torque vectoring differential. As technology in the automotive industry improves, more vehicles are equipped with torque vectoring differentials. This allows for the wheels to grip the road for better launch and handling.
This glossary of automotive terms is a list of definitions of terms and concepts related to automobiles, including their parts, operation, and manufacture, as well as automotive engineering, auto repair, and the automotive industry in general. For more specific terminology regarding the design and classification of various automobile styles, see Glossary of automotive design; for terms related to transportation by road, see Glossary of road transport terms; for competitive auto racing, see Glossary of motorsport terms.
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