Automobile layout
Encyclopedia
In automotive design
, the automobile layout describes where on the vehicle the engine
and drive wheel
s are found. Many different combinations of engine location and driven wheels are found in practice, and the location of each is dependent on the application the vehicle will be used for. Factors influencing the design choice include cost, complexity, reliability, packaging (location and size of the passenger compartment and boot
), weight distribution
and the vehicle's intended handling characteristics
.
Layouts can roughly be divided into two categories: front- or rear-wheel drive. Four-wheel-drive vehicles may take on the characteristics of either, depending on how power is distributed to the wheels.
As the steered wheels are also the driven wheels, FF (front-engine, front-wheel drive layout) cars are generally considered superior to FR (front-engine, rear-wheel drive layout) cars in conditions such as snow, mud or wet tarmac. However, powerful cars rarely use the FF layout because weight transference under acceleration reduces the weight on the front wheels and reduces their traction
, putting a limit on the amount of torque which can be utilized. Electronic traction control
can avoid wheelspin but largely negates the benefit of extra torque/power.
A transverse engine
(also known as "east-west") is commonly used in FF designs, in contrast to FR which uses a longitudinal engine
. The FF layout also restricts the size of the engine that can be placed in modern engine compartments, as FF configurations usually have Inline-4 and V6 engines, while longer engines such as Inline-6 and 90° V8 will rarely fit. This is another reason luxury/sports cars almost never use the FF layout; an exception is the Volvo S80
(FWD/4WD) which uses transversely mounted inline 6 and V8 engines.
Most Audi
s are FF layout cars, but with longitudinal engine
s, such as the Audi A4
and Audi A6
, however "FrontTrak" front-wheel drive models are only entry-level trims in the United States and Canada; most Audis usually come with "quattro" all-wheel drive. The Audi A3
is a FF layout car with a traverse engine mounting, as it does not share a platform with more expensive offerings in the marque.
is a single unit contained in the engine compartment of the vehicle and there is no need to devote interior space for a driveshaft
tunnel or rear differential, increasing the volume available for passengers and cargo. There are some exceptions to this as rear engine designs do not take away interior space. (See Porsche 911
, and Volkswagen Beetle
) It also has fewer components overall and thus lower weight. The direct connection between engine and transaxle reduces the mass and mechanical inertia
of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economy
. In front wheel drive cars the mass of the drivetrain is placed over the driven wheels and thus moves the center of gravity
farther forward than a comparable rear-wheel drive layout, improving traction
and directional stability on wet, snowy, or icy surfaces. Front-wheel drive cars, with a front weight bias, tend to understeer
at the limit, which according to, for instance, Saab engineer Gunnar Larsson, is easier since it makes instinct correct in avoiding terminal oversteer, and less prone to result in fishtailing
or a spin.
According to a sales brochure for the 1989 Lotus Elan
, the ride and handling engineers at Lotus
found that "for a given vehicle weight, power and tire size, a front wheel drive car was always faster over a given section of road." However, this may only apply for cars with moderate power-to-weight ratio. According to road test with two Dodge Daytona
s, one FWD and one RWD, the road layout is also important for what configuration is the fastest.
The lack of weight shifting limits the acceleration of a front-wheel drive vehicle. During heavy acceleration, weight is shifted to the back, improving traction
at the rear wheels at the expense of the front driving wheels; consequently, most racing cars are rear-wheel drive for acceleration. However, since front-wheel drive cars have the weight of the engine over the driving wheels, the problem only applies in extreme conditions. The weight shifting and weight distribution of rear wheel drive cars make them more likely to oversteer and the related problem of fishtailing
. On snow, ice, and sand, rear-wheel drive loses its traction advantage to front or all-wheel drive vehicles which have greater weight over the driven wheels. Rear wheel drive cars with rear engine or mid engine configuration retain traction over the driven wheels, although fishtailing remains an issue. Some rear engine cars (e.g. Porsche 911
) can suffer from reduced steering ability under heavy acceleration, since the engine is outside the wheelbase and at the opposite end of the car from the wheels doing the steering. A rear wheel drive car's center of gravity is shifted rearward when heavily loaded with passengers or cargo, which may cause unpredictable handling behavior.
On FR cars, the long driveshaft adds to drivetrain elasticity.
(FR layout). The front mid-engine, rear mid-engine and rear engine
layouts are also used. This was the traditional automobile layout for most of the 20th century. Nearly all motorcycle
s and bicycle
s use rear-wheel drive, either by driveshaft
, chain
, or belt
, since the front wheel is turned for steering, and it would be very difficult and cumbersome to "bend" the drive mechanism around the turn of the front wheel.
in the front of the vehicle, driving the rear wheels via a driveshaft
linked via a differential
between the rear axles. Some FR layout vehicles place the gearbox at the rear, though most attach it to the engine at the front.
The FR layout is often chosen for its simple design and good handling characteristics. Placing the drive wheels at the rear allows ample room for the transmission in the center of the vehicle and avoids the mechanical complexities associated with transmitting power to the front wheels. For performance-oriented vehicles, the FR layout is more suitable than front-wheel drive designs, especially with engines that exceed 200 horsepower
. This is because weight transfers to the rear of the vehicle during acceleration, which loads the rear wheels and increases their grip.
Another advantage of the FR layout is relatively easy access to the engine compartment, as result of the longitudinal orientation of the drivetrain
, as compared to the FF layout (front-engine, front-wheel drive). Powerful engines such as the Inline-6 and 90° big-bore V8 are usually too long to fit in a FF transverse engine
("east-west") layout; the FF configuration can typically accommodate at the maximum an Inline-4 or V6. This is another reason luxury/sports cars almost never use the FF layout.
Most 4WD layouts are front-engined and are derivatives of earlier front-engined, two-wheel drive designs. They fall into two major categories:
For a full explanation of 4WD engineering considerations, see the main article on four-wheel drive
model, so this layout was known as the "Système Panhard" in the early years. Most American cars used the FR layout until the mid 1980s. The Oil crisis
of the 1970s and the success of small FF cars like the Mini
, Volkswagen Golf
, Toyota Tercel
, and Honda Civic
led to the widespread adoption of that layout.
After the Arab Oil Embargo of 1973 and the 1979 fuel crises, a majority of American FR vehicles (station wagons, luxury sedans) were phased out for the FF layout — this trend would spawn the SUV/van conversion market. Throughout the 1980s and 1990s, most American companies set as a priority the eventual removal of rear-wheel drive from their mainstream and luxury lineup. Chrysler went 100% FF by 1990 and GM
's American production went entirely FF by 1997 except the Corvette
and Camaro. Ford's full-size cars (the Ford Crown Victoria
, Mercury Grand Marquis
, and Lincoln Town Car
) have always been FR, as was the Ford Mustang
and Lincoln LS
. In 2008 Hyundai
introduced its own rear-wheel drive car, the Hyundai Genesis
.
In Australia, FR cars have remained popular throughout this period, with the Holden Commodore
and Ford Falcon
having consistently strong sales. In Europe, front-wheel drive was popularized by small cars like the Mini
, Renault 5
and Volkswagen Golf
and adopted for virtually all mainstream cars.
Upscale marques like Mercedes-Benz
, BMW
, and Jaguar remained mostly independent of this trend, and retained a lineup mostly or entirely made up of FR cars. Japanese mainstream marques such as Toyota and Nissan became mostly or entirely FF early on, while reserving for their latterly-conceived luxury divisions (Lexus
and Infiniti
, respectively) a mostly FR lineup. While many automakers lost sight of the true sports car, Mazda
introduced the highly successful Miata roadster in 1990, a true 2-seater sports car using the traditional FR layout which led to other compaines such as General Motors to produce a FR sports car based on their Kappa
platform.
Currently most cars are FF, including virtually all front-engined economy cars, though FR cars are making a return as an alternative to large sport-utility vehicles. In North America, GM returned to production of the FR luxury car with the 2003 Cadillac CTS
, and with the removal of the DTS
, Cadillac will be entirely FR (with four-wheel drive available as an option on several models) by 2010, and the 2010 Camaro returns as a FR sports car. Chrysler
returned its full-size cars to this layout with the Chrysler 300
and related models. Ford never eliminated FR cars, but is looking to replace the dated designs that it currently has. Nissan are also bringing back the Silvia to their line-up, Mazda
is said to be releasing a new rotary-powered FR car in their RX line-up by 2010 and there are rumours Toyota are bringing a successor to the AE86, in other words, an affordable RWD car. Hyundai
introduced their affordable RWD car being the 2009 Hyundai Genesis
and 2010 Hyundai Genesis Coupe
In the 21st century, with solutions to the engineering complexities of 4WD being widely understood, and consumer demand for increasing performance in production cars, front-engined 4WD layouts are rapidly becoming more common, and most major manufacturers now offer 4WD options on at least some models. Manufacturers with a notable expertise and history in producing 4WD performance cars are Audi
and Subaru
.
Automotive design
Automotive design is the profession involved in the development of the appearance, and to some extent the ergonomics, of motor vehicles or more specifically road vehicles. This most commonly refers to automobiles but also refers to motorcycles, trucks, buses, coaches, and vans...
, the automobile layout describes where on the vehicle the engine
Engine
An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...
and drive wheel
Drive wheel
A drive wheel is a roadwheel in an automotive vehicle that receives torque from the powertrain, and provides the final driving force for a vehicle. A two-wheel drive vehicle has two driven wheels, and a four-wheel drive has four, and so-on....
s are found. Many different combinations of engine location and driven wheels are found in practice, and the location of each is dependent on the application the vehicle will be used for. Factors influencing the design choice include cost, complexity, reliability, packaging (location and size of the passenger compartment and boot
Trunk (automobile)
The trunk or boot of an automobile or car is the vehicle's main storage, luggage, or cargo compartment. Trunk is used in North American English and Jamaican English; boot is used elsewhere in the English speaking world. Trunk is also primarily used in many non-English speaking regions, such as...
), weight distribution
Weight distribution
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes, and trains.In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including handling, acceleration, traction, and component life...
and the vehicle's intended handling characteristics
Car handling
Automobile handling and vehicle handling are descriptions of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving. It also includes their stability when moving at rest. Handling and braking are the major components of a vehicle's...
.
Layouts can roughly be divided into two categories: front- or rear-wheel drive. Four-wheel-drive vehicles may take on the characteristics of either, depending on how power is distributed to the wheels.
Front-wheel drive layouts
Front-wheel-drive layouts are those in which the front wheels of the vehicle are driven. The most popular layout used in cars today is the front-engine, front-wheel drive, with the engine in front of the front axle, driving the front wheels. This layout is typically chosen for its compact packaging; since the engine and driven wheels are on the same side of the vehicle, there is no need for a central tunnel through the passenger compartment to accommodate a prop-shaft between the engine and the driven wheels.As the steered wheels are also the driven wheels, FF (front-engine, front-wheel drive layout) cars are generally considered superior to FR (front-engine, rear-wheel drive layout) cars in conditions such as snow, mud or wet tarmac. However, powerful cars rarely use the FF layout because weight transference under acceleration reduces the weight on the front wheels and reduces their traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
, putting a limit on the amount of torque which can be utilized. Electronic traction control
Traction control system
A traction control system , also known as anti-slip regulation , is typically a secondary function of the anti-lock braking system on production motor vehicles, designed to prevent loss of traction of driven road wheels...
can avoid wheelspin but largely negates the benefit of extra torque/power.
A transverse engine
Transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
(also known as "east-west") is commonly used in FF designs, in contrast to FR which uses a longitudinal engine
Longitudinal engine
In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
. The FF layout also restricts the size of the engine that can be placed in modern engine compartments, as FF configurations usually have Inline-4 and V6 engines, while longer engines such as Inline-6 and 90° V8 will rarely fit. This is another reason luxury/sports cars almost never use the FF layout; an exception is the Volvo S80
Volvo S80
The Volvo S80 is a mid-size executive saloon/sedan from Swedish automaker Volvo Cars, and was introduced in 1998 to take the place of the rear-wheel drive Volvo 960/S90 saloons in the model range. The Volvo S80 was built at the Torslanda Plant in Gothenburg, Sweden. Unlike most Volvo models, it...
(FWD/4WD) which uses transversely mounted inline 6 and V8 engines.
Most Audi
Audi
Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....
s are FF layout cars, but with longitudinal engine
Longitudinal engine
In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
s, such as the Audi A4
Audi A4
The first generation Audi A4 debuted in 1994, with production starting November 1994. It was built on the Volkswagen Group B5 platform, which it shared with the fourth generation Volkswagen Passat . It had a front-mounted longitudinal engine and front-wheel drive...
and Audi A6
Audi A6
The Audi A6 is an executive car marketed by the German automaker Audi AG, now in its fourth generation. As the successor to the Audi 100, the A6 is manufactured in Neckarsulm, Germany – and is available in saloon, and wagon configurations, the latter marketed by Audi as the Avant.All generations...
, however "FrontTrak" front-wheel drive models are only entry-level trims in the United States and Canada; most Audis usually come with "quattro" all-wheel drive. The Audi A3
Audi A3
The Audi A3 is a small family car produced by the German automaker Audi since 1996. Two generations of A3 exist, both based on the Volkswagen Group A platform, which they share with several other models such as the Audi TT, Volkswagen Golf, Volkswagen Caddy and Volkswagen Touran as well as SEAT...
is a FF layout car with a traverse engine mounting, as it does not share a platform with more expensive offerings in the marque.
Characteristics
Front-wheel drive gives more interior space since the powertrainPowertrain
In a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...
is a single unit contained in the engine compartment of the vehicle and there is no need to devote interior space for a driveshaft
Driveshaft
A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
tunnel or rear differential, increasing the volume available for passengers and cargo. There are some exceptions to this as rear engine designs do not take away interior space. (See Porsche 911
Porsche 911
The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
, and Volkswagen Beetle
Volkswagen Beetle
The Volkswagen Type 1, widely known as the Volkswagen Beetle or Volkswagen Bug, is an economy car produced by the German auto maker Volkswagen from 1938 until 2003...
) It also has fewer components overall and thus lower weight. The direct connection between engine and transaxle reduces the mass and mechanical inertia
Inertia
Inertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economy
Fuel economy in automobiles
Fuel usage in automobiles refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed....
. In front wheel drive cars the mass of the drivetrain is placed over the driven wheels and thus moves the center of gravity
Center of gravity
In physics, a center of gravity of a material body is a point that may be used for a summary description of gravitational interactions. In a uniform gravitational field, the center of mass serves as the center of gravity...
farther forward than a comparable rear-wheel drive layout, improving traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
and directional stability on wet, snowy, or icy surfaces. Front-wheel drive cars, with a front weight bias, tend to understeer
Understeer
Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns by more than the amount commanded by the driver...
at the limit, which according to, for instance, Saab engineer Gunnar Larsson, is easier since it makes instinct correct in avoiding terminal oversteer, and less prone to result in fishtailing
Fishtailing
Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...
or a spin.
According to a sales brochure for the 1989 Lotus Elan
Lotus Elan
Lotus Elan is the name of two convertible cars and one fixed head coupé produced by Lotus Cars. The original Type 26, 26R Racing version , 36R Racing version , 36 Fixed Head Coupe, 45 Drop Head Coupe, and the "Type 50" +2 Coupe, circa 1962 to 1975, are commonly known as the '60s Elans...
, the ride and handling engineers at Lotus
Lotus Cars
Lotus Cars is a British manufacturer of sports and racing cars based at the former site of RAF Hethel, a World War II airfield in Norfolk. The company designs and builds race and production automobiles of light weight and fine handling characteristics...
found that "for a given vehicle weight, power and tire size, a front wheel drive car was always faster over a given section of road." However, this may only apply for cars with moderate power-to-weight ratio. According to road test with two Dodge Daytona
Dodge Daytona
The first car that carried the Daytona name was a sporty version of the Studebaker Lark which was produced from 1963 to 1966 with standard bucket seats and available with an optional Studebaker Avanti V8 high-performance engine....
s, one FWD and one RWD, the road layout is also important for what configuration is the fastest.
The lack of weight shifting limits the acceleration of a front-wheel drive vehicle. During heavy acceleration, weight is shifted to the back, improving traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
at the rear wheels at the expense of the front driving wheels; consequently, most racing cars are rear-wheel drive for acceleration. However, since front-wheel drive cars have the weight of the engine over the driving wheels, the problem only applies in extreme conditions. The weight shifting and weight distribution of rear wheel drive cars make them more likely to oversteer and the related problem of fishtailing
Fishtailing
Fishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...
. On snow, ice, and sand, rear-wheel drive loses its traction advantage to front or all-wheel drive vehicles which have greater weight over the driven wheels. Rear wheel drive cars with rear engine or mid engine configuration retain traction over the driven wheels, although fishtailing remains an issue. Some rear engine cars (e.g. Porsche 911
Porsche 911
The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
) can suffer from reduced steering ability under heavy acceleration, since the engine is outside the wheelbase and at the opposite end of the car from the wheels doing the steering. A rear wheel drive car's center of gravity is shifted rearward when heavily loaded with passengers or cargo, which may cause unpredictable handling behavior.
On FR cars, the long driveshaft adds to drivetrain elasticity.
Advantages
- Interior space: Since the powertrainPowertrainIn a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...
is a single unit contained in the engine compartment of the vehicle, there is no need to devote interior space for a driveshaftDriveshaftA drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
tunnel or rear differential, increasing the volume available for passengers and cargo.- Instead, the tunnel may be used to route the exhaust system pipes.
- Weight: Fewer components usually means lower weight.
- Improved fuel efficiencyFuel efficiencyFuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...
due to less weight. - Cost: Fewer material components and less installation complexity overall. However, the considerable MSRPSuggested retail priceThe manufacturer's suggested retail price , list price or recommended retail price of a product is the price which the manufacturer recommends that the retailer sell the product. The intention was to help to standardise prices among locations...
differential between a FF and FR car cannot be attributed to layout alone. The difference is more probably explained by production volumes as most rear-wheel cars are usually in the sports/performance/luxury categories (which tend to be more upscale and/or have more powerful engines), while the FF configuration is typically in mass-produced mainstream cars. Few modern "family" cars have rear-wheel drive as of 2009, so a direct cost comparison is not necessarily possible. A contrast could be somewhat drawn between the Audi A4Audi A4The first generation Audi A4 debuted in 1994, with production starting November 1994. It was built on the Volkswagen Group B5 platform, which it shared with the fourth generation Volkswagen Passat . It had a front-mounted longitudinal engine and front-wheel drive...
FrontTrak (which has an FF layout and front-wheel drive) and a rear-wheel drive BMW 3-Series (which is FR), both which are in the compact executive carCompact executive carCompact executive car is a car classification term applied to premium cars smaller than executive cars. In European classification, compact executive cars are part of the D-segment. In North American terms, close equivalents are compact premium car, compact luxury car, entry-level luxury car and...
classification. - Improved drivetrain efficiency: the direct connection between engine and transaxle reduce the mass and mechanical inertiaInertiaInertia is the resistance of any physical object to a change in its state of motion or rest, or the tendency of an object to resist any change in its motion. It is proportional to an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to...
of the drivetrain compared to a rear-wheel drive vehicle with a similar engine and transmission, allowing greater fuel economyFuel economy in automobilesFuel usage in automobiles refers to the fuel efficiency relationship between distance traveled by an automobile and the amount of fuel consumed....
. - Assembly efficiency: the powertrain can often be assembled and installed as a unit, which allows more efficient production.
- Placing the mass of the drivetrain over the driven wheels moves the centre of gravity farther forward than a comparable rear-wheel drive layout, improving tractionTraction (engineering)Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
and directional stability on wet, snowy, or icy surfaces. - Predictable handling characteristics: front-wheel drive cars, with a front weight bias, tend to understeerUndersteerUndersteer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns by more than the amount commanded by the driver...
at the limit, which (according to e.g. SAAB engineer Gunnar Larsson) is easier since it makes instinct correct in avoiding terminal oversteer, and less prone to result in fishtailingFishtailingFishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...
or a spin. - A skilled driver can control the movement of the car even while skidding by steering, throttling and pulling the hand brake (given that the hand brake operates the rear wheels as in most cases, with some CitroenCitroënCitroën is a major French automobile manufacturer, part of the PSA Peugeot Citroën group.Founded in 1919 by French industrialist André-Gustave Citroën , Citroën was the first mass-production car company outside the USA and pioneered the modern concept of creating a sales and services network that...
and SaabSaabSaab AB is a Swedish aerospace and defence company, founded in 1937. From 1947 to 1990 it was the parent company of automobile manufacturer Saab Automobile, and between 1968 and 1995 the company was in a merger with commercial vehicle manufacturer Scania, known as Saab-Scania.-History:"Svenska...
models being notable exceptions). A small car with the FF layout is superior for motor sport events focusing on manouvreability such as AutotestingAutotestingAutotesting involves a series of tests, generally around traffic cones, to measure precision driving skill. The tests often include stopping with the front and rear wheels straddling a line, and always end stopping in a garage . Sections of each test are usually completed in reverse... - It is easier to correct trailing-throttle or trailing-brake oversteerLift-off oversteerLift-off oversteer is a form of oversteer in an automobile that occurs when the vertical load on the tires shifts from the rear to the front quickly due to throttle release while cornering...
. - The wheelbase can be extended without building a longer driveshaft (as with rear wheel driven cars).
Disadvantages
- Front-engine front-wheel drive layouts are "nose heavy" with more weight distribution forward, which makes them prone to understeerUndersteerUndersteer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns by more than the amount commanded by the driver...
, especially in high horsepower applications. Enthusiast driver aids, such as active rear differential, active steering, and ultra-quick electrically-adjustable shocks, can negate the understeer problem and allow the car to perform as well as a front-engine rear-wheel drive car (such as the BMW 3 SeriesBMW 3 SeriesThe BMW 3 Series is a compact executive car manufactured by the German automaker BMW since May 1975. Successor to the BMW New Class, it has been produced in five different generations and in no less than five different body styles. It is BMW's best-selling model, accounting for around 30% of the...
). These trick differentials, which are found on the 2009 Acura TLAcura TLThe TL "Touring Luxury" debuted as 1996 model, first with the 1996 2.5 TL available with the 2.5 L 176 hp SOHC 20-valve 5-cylinder engine from the Vigor. The 3.2 TL used the 3.2 L 200 hp SOHC 24v V6 from the second generation Acura Legend. The 2.5 TL was positioned as the...
SH-AWD and 2010 Audi S4Audi S4The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan...
3.0 TFSI quattro, and 2011 Audi RS5 4.2 FSI quattro, are heavy, complex, and expensive. - Torque steer is the tendency for some front-wheel drive cars to pull to the left or right under hard acceleration. It is a result of the offset between the point about which the wheel steers (it is aligned with the points where the wheel is connected to the steering mechanisms) and the centroid of its contact patchContact patchContact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...
. The tractive force acts through the centroid of the contact patch, and the offset of the steering point means that a turning moment about the axis of steering is generated. In an ideal situation, the left and right wheels would generate equal and opposite moments, canceling each other out; however, in reality, this is less likely to happen. Torque steer can be addressed by using a longitudinal layout, equal length drive shafts, half shafts, a multilink suspension or centre-point steering geometry. - Lack of weight shifting will limit the acceleration of a front-wheel drive vehicle. In a vehicle, the weight shifts back during acceleration, giving more traction to the rear wheels. This is one of the main reasons why nearly all racing cars are rear-wheel drive. However, since front-wheel drive cars have the weight of the engine over the driving wheels, the problem only applies in extreme conditions.
- In some towing situations, front-wheel drive cars can be at a traction disadvantage since there will be less weight on the driving wheels. Because of this, the weight that the vehicle is rated to safely tow is likely to be less than that of a rear-wheel drive or four-wheel drive vehicle of the same size and power.
- Traction can be reduced while attempting to climb a slope in slippery conditions such as snow- or ice-covered roadways.
- Due to geometry and packaging constraints, the CV joints (constant-velocity jointConstant-velocity jointConstant-velocity joints allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. They are mainly used in front wheel drive and all wheel drive cars...
s) attached to the wheel hub have a tendency to wear out much earlier than the universal jointUniversal jointA universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any direction, and is commonly used in shafts that transmit rotary motion...
s typically used in their rear-wheel drive counterparts (although rear-wheel drive vehicles with independent rear suspension also employ CV joints and half-shafts). The significantly shorter drive axles on a front-wheel drive car causes the joint to flex through a much wider degree of motion, compounded by additional stress and angles of steering, while the CV joints of a rear wheel drive car regularly see angles and wear of less than half that of front wheel drive vehicles. - Turning circle — FF layouts almost always use a Transverse engineTransverse engineA transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
("east-west") installation, which limits the amount by which the front wheels can turn, thus increasing the turning circle of a front-wheel drive car compared to a rear-wheel drive one with the same wheelbase. A notable example is the original MiniMiniThe Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...
. It is widely misconceived that this limitation is due to a limit on the angle at which a CV joint can be operated, but this is easily disproved by considering the turning circle of car models that use a longitudinal FF or F4 layout from AudiAudiAudi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....
and (prior to 1992) SaabSaabSaab AB is a Swedish aerospace and defence company, founded in 1937. From 1947 to 1990 it was the parent company of automobile manufacturer Saab Automobile, and between 1968 and 1995 the company was in a merger with commercial vehicle manufacturer Scania, known as Saab-Scania.-History:"Svenska... - The FF transverse engineTransverse engineA transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
layout (also known as "east-west") restricts the size of the engine that can be placed in modern engine compartments, so it is rarely adopted by powerful luxury and sports cars. FF configurations can usually only accommodate Inline-4 and V6 engines, while longer engines such as Inline-6 and 90° big-bore V8 will rarely fit, though there are exceptions. One way around this problem is using a staggered engineVR6 engineThe VR6 engine is an internal combustion engine configuration, consisting of six cylinders. It was developed by the Volkswagen Group in the late 1980s, and evolutions of the original variant are still produced by them....
. - It makes heavier use of the front tires (i.e. accelerating, braking, and turning), causing more wear in the front than in a rear wheel drive layout.
Rear wheel drive layouts
Rear-wheel drive (RWD) typically places the engine in the front of the vehicle and the driven wheels are located at the rear, a configuration known as front-engine, rear-wheel drive layoutFront-engine, rear-wheel drive layout
In automotive design, an FR, or Front-engine, Rear-wheel drive layout is one where the engine is located at the front of the vehicle and driven wheels are located at the rear. This was the traditional automobile layout for most of the 20th century....
(FR layout). The front mid-engine, rear mid-engine and rear engine
RR layout
In automotive design, a RR, or Rear-engine, Rear-wheel drive layout places both the engine and drive wheels at the rear of the vehicle. In contrast to the RMR layout, the center of mass of the engine is between the rear axle and the rear bumper....
layouts are also used. This was the traditional automobile layout for most of the 20th century. Nearly all motorcycle
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
s and bicycle
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
s use rear-wheel drive, either by driveshaft
Driveshaft
A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
, chain
Chain drive
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles...
, or belt
Belt (mechanical)
A belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the...
, since the front wheel is turned for steering, and it would be very difficult and cumbersome to "bend" the drive mechanism around the turn of the front wheel.
Characteristics
The vast majority of rear-wheel drive vehicles use a longitudinally-mounted engineLongitudinal engine
In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
in the front of the vehicle, driving the rear wheels via a driveshaft
Driveshaft
A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
linked via a differential
Differential (mechanics)
A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles—and in the other way, it...
between the rear axles. Some FR layout vehicles place the gearbox at the rear, though most attach it to the engine at the front.
The FR layout is often chosen for its simple design and good handling characteristics. Placing the drive wheels at the rear allows ample room for the transmission in the center of the vehicle and avoids the mechanical complexities associated with transmitting power to the front wheels. For performance-oriented vehicles, the FR layout is more suitable than front-wheel drive designs, especially with engines that exceed 200 horsepower
Horsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
. This is because weight transfers to the rear of the vehicle during acceleration, which loads the rear wheels and increases their grip.
Another advantage of the FR layout is relatively easy access to the engine compartment, as result of the longitudinal orientation of the drivetrain
Longitudinal engine
In automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
, as compared to the FF layout (front-engine, front-wheel drive). Powerful engines such as the Inline-6 and 90° big-bore V8 are usually too long to fit in a FF transverse engine
Transverse engine
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
("east-west") layout; the FF configuration can typically accommodate at the maximum an Inline-4 or V6. This is another reason luxury/sports cars almost never use the FF layout.
Advantages
- Even weight distribution — The layout of a rear-wheel drive car is much closer to an even fore-and-aft weight distribution than a front-wheel-drive car, as more of the engine can lie between the front and rear wheels (in the case of a mid engine layout, the entire engine), and the transmission is moved much farther back.
- Weight transferWeight transferWeight 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, and the change in center of mass location relative to the wheels because of...
during acceleration — During heavy acceleration, weight is placed on the rear, or driving wheels, which improves tractionTraction (engineering)Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
. - No torque steerTorque steeringTorque steering is the influence of engine torque on the steering for some front-wheel drive vehicles. For example, during heavy acceleration the steering may pull to one side, which may be disturbing to the driver. The effect is manifested either as a tugging sensation in the steering wheel, or a...
(unless it's an all-wheel steer with an offset differential). - Steering radius — As no complicated drive shaft joints are required at the front wheels, it is possible to turn them further than would be possible using front-wheel drive, resulting in a smaller steering radius for a given wheelbase.
- Better handlingCar handlingAutomobile handling and vehicle handling are descriptions of the way wheeled vehicles perform transverse to their direction of motion, particularly during cornering and swerving. It also includes their stability when moving at rest. Handling and braking are the major components of a vehicle's...
in dry conditions — the more even weight distribution and weight transfer improve the handling of the car. The front and rear tires are placed under more even loads, which allows for more grip while cornering. - Better braking — the more even weight distribution helps prevent lockup from wheels becoming unloaded under heavy braking.
- Towing — Rear wheel drive puts the wheels which are pulling the load closer to the point where a trailer articulates, helping steering, especially for large loads.
- Serviceability — Drivetrain components on a rear-wheel drive vehicle are modular and do not involve packing as many parts into as small a space as does front wheel drive, thus requiring less disassembly or specialized tools in order to service the vehicle.
- Robustness — due to geometry and packaging constraints, the universal joints attached to the wheel hub have a tendency to wear out much later than the CV jointsConstant-velocity jointConstant-velocity joints allow a drive shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or play. They are mainly used in front wheel drive and all wheel drive cars...
typically used in front-wheel drive counterparts. The significantly shorter drive axles on a front-wheel drive car causes the joint to flex through a much wider degree of motion, compounded by additional stress and angles of steering, while the CV joints of a rear wheel drive car regularly see angles and wear of less than half that of front wheel drive vehicles. - Can accommodate more powerful engines as a result of the longitudinal orientation of the drivetrainLongitudinal engineIn automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
, such as the Inline-6 and 90° big-bore V8, making the FR a common configuration for luxury and sports cars. These engines are usually too long to fit in a FF transverse engineTransverse engineA transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
("east-west") layout; the FF configuration can typically accommodate at the maximum an Inline-4 or V6.
Disadvantages
- Under heavy acceleration, oversteer and fishtailingFishtailingFishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...
may occur. - On snow, ice and sand, rear-wheel drive loses its traction advantage to front- or all-wheel drive vehicles, which have greater weight on the driven wheels. Rear-wheel-drive cars with rear engine or mid engine configuration do not suffer from this, although fishtailingFishtailingFishtailing is a vehicle handling problem which occurs when the rear wheels lose traction, resulting in oversteer. This can be caused by low friction surfaces...
remains an issue. - Some rear engine cars (e.g. Porsche 911Porsche 911The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
) can suffer from reduced steering ability under heavy acceleration, because the engine is outside the wheelbase and at the opposite end of the car from the wheels doing the steering although the engine weight over the rear wheels provides outstanding traction and grip during acceleration. - Decreased interior space — Though individual designs vary greatly, rear wheel drive vehicles may have: Less front leg room as the transmission tunnel takes up a space between the driver and front passenger, less leg room for center rear passengers (due to the tunnel needed for the drive shaft), often no seat for a center rear passenger, and sometimes less bootTrunk (automobile)The trunk or boot of an automobile or car is the vehicle's main storage, luggage, or cargo compartment. Trunk is used in North American English and Jamaican English; boot is used elsewhere in the English speaking world. Trunk is also primarily used in many non-English speaking regions, such as...
space (since there is also more hardware that must be placed underneath the boot). Rear engine designs (such as the Porsche 911Porsche 911The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
and Volkswagen BeetleVolkswagen BeetleThe Volkswagen Type 1, widely known as the Volkswagen Beetle or Volkswagen Bug, is an economy car produced by the German auto maker Volkswagen from 1938 until 2003...
) do not inherently take away interior space. - Increased weight — The components of a rear wheel drive vehicle's power train are less complex, but they are larger. The driveshaft adds weight. There is extra sheet metal to form the transmission tunnel. There is a rear axleAxleAn axle 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 its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
or rear half-shafts, which are typically longer than those in a front-wheel drive car. A rear wheel drive car will weigh slightly more than a comparable front wheel drive car (but less than four wheel drive). - Improper weight distribution when loaded — A rear wheel drive car's center of gravity is shifted rearward when heavily loaded with passengers or cargo, which may cause unpredictable handling behavior.
- Higher initial purchase price — Modern rear wheel drive vehicles are typically more expensive to purchase than comparable front wheel drive vehicles. Part of this can be explained by the added cost of materials and increased complex assembly of FR layouts, as the powertrainPowertrainIn a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive...
is not one compact unit. However, the difference is more probably explained by production volumes as most rear-wheel cars are usually in the sports/performance/luxury categories (which tend to be more upscale and/or have more powerful engines), while the FF configuration is typically in mass-produced mainstream cars. - The possibility of a slight loss in the mechanical efficiency of the drivetrain (approximately 17% coastdown losses between engine flywheel and road wheels compared to 15% for front wheel drive — however these losses are highly dependent on the individual transmission). Cars with rear engine or mid engine configuration and a transverse engine layout do not suffer from this.
- The long driveshaftDriveshaftA drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
(on front engine cars) adds to drivetrain elasticity. The driveshaft must also be extended for cars with a stretched wheelbase (e.g. limousines, minivans). - When shifting down at high RPM, rear-wheel drive vehicles tend to oversteer if the clutch is not released correctly.
Four wheel drive layouts
Note: in North America, Australia and New Zealand the term "four-wheel drive" usually refers only to drivetrains which are primarily two-wheel drive with a part-time four-wheel drive capability, as typically found in pickup trucks and other off road vehicles, while the term "all-wheel drive" is used to refer to full time four-wheel drive systems found in performance cars and smaller car-based SUVs. This section uses the term four-wheel drive to refer to both.Most 4WD layouts are front-engined and are derivatives of earlier front-engined, two-wheel drive designs. They fall into two major categories:
- Front-engine, rear-wheel driveFront-engine, rear-wheel drive layoutIn automotive design, an FR, or Front-engine, Rear-wheel drive layout is one where the engine is located at the front of the vehicle and driven wheels are located at the rear. This was the traditional automobile layout for most of the 20th century....
derived 4WD systems, standard in most sport utility vehicleSport utility vehicleA sport utility vehicle is a generic marketing term for a vehicle similar to a station wagon, but built on a light-truck chassis. It is usually equipped with four-wheel drive for on- or off-road ability, and with some pretension or ability to be used as an off-road vehicle. Not all four-wheel...
s and in passenger cars, (usually referred to “front engine, rear-wheel drive/four-wheel drive”), forerunners of today models include the Jensen FFJensen FFThe Jensen FF was a four-wheel drive Grand Tourer car produced by the British manufacturer Jensen Motors between 1966 and 1971. It was the first non all-terrain production car equipped with 4WD and an anti-lock braking system — the Dunlop Maxaret mechanical system used hitherto only on...
, AMC EagleAMC EagleThe AMC Eagle is a compact-sized four-wheel drive passenger vehicle that was produced by American Motors Corporation . The AMC Eagle line of vehicles inaugurated a new product category of "sport-utility" or crossover SUV....
and Mercedes-Benz W124Mercedes-Benz W124W124 is the Mercedes-Benz internal chassis-designation for the 1985 to 1995 version of the Mercedes-Benz E-Class. The W124 models replaced the W123 models after 1985 and were superseded by the W210 E-Class after 1995.-History:...
with the 4Matic4MATIC4Matic is the name of an AWD four-wheel drive system developed and used by Mercedes-Benz. It is designed to increase traction in slippery conditions....
system and Suzuki Grand Vitara with/without 4 mode transfer case. - TransverseTransverse engineA transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the long axis of the vehicle. Many modern front wheel drive vehicles use this engine mounting configuration...
and longitudinal engineLongitudinal engineIn automotive engineering, a longitudinal engine is an internal combustion engine in which the crankshaft is oriented along the long axis of the vehicle, front to back....
d 4WD systems derived almost exclusively from front-engined, front-drive layoutsFront-wheel driveFront-wheel drive is a form of engine/transmission layout used in motor vehicles, where the engine drives the front wheels only. Most modern front-wheel drive vehicles feature a transverse engine, rather than the conventional longitudinal engine arrangement generally found in rear-wheel drive and...
, fitted to luxury, sporting and heavy duty segments, for example the transverse-engined Mitsubishi 3000GT VR-4Mitsubishi GTOThe Mitsubishi GTO is a sports car built by Japanese automaker Mitsubishi Motors between 1990 and 2001. In most export markets it was rebadged as a Mitsubishi 3000GT. It was also sold by Chrysler in North America as a Dodge Stealth captive import from the 1991 to 1996 model years with only minor...
and Toyota RAV4Toyota RAV4The Toyota RAV4 is a compact crossover SUV from Toyota. It was the first compact crossover SUV, introduced in Japan and Europe in 1994 and beginning sales in North America in 1996...
and the longitudinal-engined Audi QuattroAudi QuattroThe Audi Quattro is a road and rally car, produced by the German automobile manufacturer Audi, now part of the Volkswagen Group. It was first shown at the 1980 Geneva Motor Show on 3 March.The word quattro is derived from the Italian word for "four"...
and most of the SubaruSubaru; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
line.
For a full explanation of 4WD engineering considerations, see the main article on four-wheel drive
Four-wheel drive
Four-wheel drive, 4WD, or 4×4 is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously...
Advantages
In terms of handling, traction and performance, 4WD systems generally have most of the advantages of both front-wheel drive and rear-wheel drive. Some unique benefits are:- Traction is nearly doubled compared to a two-wheel drive layout. Given sufficient power, this results in unparalleled acceleration and driveability on surfaces with less than ideal grip, and superior engine braking on loose surfaces. The development of 4WD systems for high performance cars was stimulated primarily by rallyingRallyingRallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...
. - Handling characteristics in normal conditions can be configured to emulate FWD or RWD, or some mixture, even to switch between these behaviours according to circumstance. However, at the limit of grip, a well balanced 4WD configuration will not degenerate into either understeer or oversteer, but instead break traction of all 4 wheels at the same time into a four-wheel drift. Combined with modern electronic driving aids, this flexibility allows production car engineers a wide range of freedom in selecting handling characteristics that will allow a 4WD car to be driven more safely at higher speeds by inexpert motorists than 2WD designs.
Disadvantages
- 4WD systems require more machinery and complex transmission components, and so increase the manufacturing cost of the vehicle and complexity of maintenance procedures and repairs compared to 2WD designs
- 4WD systems increase power-train mass, rotational inertia and power transmission losses, resulting in a reduction in performance in ideal dry conditions and increased fuel consumption compared to 2WD designs
- The handbrake cannot be used to induce over-steer for maneuvering purposes, as the drivetrain couples the front and rear axles together. To overcome this limitation, some custom prepared stage rallyRallyingRallying, also known as rally racing, is a form of auto racing that takes place on public or private roads with modified production or specially built road-legal cars...
cars have a special mechanism added to the transmission to disconnect the rear drive if the handbrake is applied while the car is moving.
Unusual 4WD layouts
- From 1989 onwards, some models of Porsche 911Porsche 911The Porsche 911 is a luxury 2-door sports coupe made by Porsche AG of Stuttgart, Germany. It has a distinctive design, rear-engined and with independent rear suspension, an evolution of the swing axle on the Porsche 356. The engine was also air-cooled until the introduction of the Type 996 in 1998...
feature a rear-engined 4WD layout, which is akin to a longitudinal front-engine 4WD layout installed backwards with the engine at the rear of the car - From 2007 onwards, the Nissan GT-RNissan GT-RThe Nissan GT-R is a sports car produced by Nissan released in Japan on December 6, 2007, the United States on July 4, 2008, and the rest of the world in March 2009.-History:...
features a front-engine 4WD longitudinal layout, but with the gearbox at the rear of the vehicle. This provides a more ideal weight balance, and improves directional stability at very high speeds by increasing the vehicle's moment of inertiaMoment of inertiaIn classical mechanics, moment of inertia, also called mass moment of inertia, rotational inertia, polar moment of inertia of mass, or the angular mass, is a measure of an object's resistance to changes to its rotation. It is the inertia of a rotating body with respect to its rotation...
around the vertical axis. This layout necessitates a second prop-shaft to carry power to the front wheels. - Some types of farm tractors and construction site machinery use a 4WD layout where the wheels on each side are coupled together, rather than the wheels on each axle, allowing these vehicles to pivot about their center point. Such vehicles are controlled in a fashion similar to a military tankTankA tank is a tracked, armoured fighting vehicle designed for front-line combat which combines operational mobility, tactical offensive, and defensive capabilities...
. - The Citroën Sahara had a 4WD system using complete Citroën 2CVCitroën 2CVThe Citroën 2CV |tax horsepower]]”) was an economy car produced by the French automaker Citroën between 1948 and 1990. It was technologically advanced and innovative, but with uncompromisingly utilitarian unconventional looks, and deceptively simple Bauhaus inspired bodywork, that belied the sheer...
drivetrains at both ends of the car, such that the engine at the front powered the front wheels and the engine at the back powered the rear wheels.
History and current use
The first FR car was an 1895 PanhardPanhard
Panhard is currently a French manufacturer of light tactical and military vehicles. Its current incarnation was formed by the acquisition of Panhard by Auverland in 2005. Panhard had been under Citroën ownership, then PSA , for 40 years...
model, so this layout was known as the "Système Panhard" in the early years. Most American cars used the FR layout until the mid 1980s. The Oil crisis
1973 oil crisis
The 1973 oil crisis started in October 1973, when the members of Organization of Arab Petroleum Exporting Countries or the OAPEC proclaimed an oil embargo. This was "in response to the U.S. decision to re-supply the Israeli military" during the Yom Kippur war. It lasted until March 1974. With the...
of the 1970s and the success of small FF cars like the Mini
Mini
The Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...
, Volkswagen Golf
Volkswagen Golf
The Volkswagen Golf is a small family car manufactured by Volkswagen since 1974 and marketed worldwide across six generations, in various body configurations and under various nameplates – as the Volkswagen Rabbit in the United States and Canada , and as the Volkswagen Caribe in Mexico .The...
, Toyota Tercel
Toyota Tercel
The Tercel is a subcompact manufactured from 1978 to 2000 across five generations, in five body configurations — sized between the Corolla and the Starlet...
, and Honda Civic
Honda Civic
The Honda Civic is a line of subcompact and subsequently compact cars made and manufactured by Honda. The Civic, along with the Accord and Prelude, comprised Honda's vehicles sold in North America until the 1990s, when the model lineup was expanded...
led to the widespread adoption of that layout.
After the Arab Oil Embargo of 1973 and the 1979 fuel crises, a majority of American FR vehicles (station wagons, luxury sedans) were phased out for the FF layout — this trend would spawn the SUV/van conversion market. Throughout the 1980s and 1990s, most American companies set as a priority the eventual removal of rear-wheel drive from their mainstream and luxury lineup. Chrysler went 100% FF by 1990 and GM
General Motors
General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...
's American production went entirely FF by 1997 except the Corvette
Chevrolet Corvette
The Chevrolet Corvette is a sports car by the Chevrolet division of General Motors that has been produced in six generations. The first model, a convertible, was designed by Harley Earl and introduced at the GM Motorama in 1953 as a concept show car. Myron Scott is credited for naming the car after...
and Camaro. Ford's full-size cars (the Ford Crown Victoria
Ford Crown Victoria
-1992–1994:Released in March 1991 as an early 1992 model, the Crown Victoria sedan was completely redesigned with a rounder, eight-window roofline . The redesign reduced the coefficient of drag from 0.42 to 0.34; the suspension setup was also heavily revised...
, Mercury Grand Marquis
Mercury Grand Marquis
The Mercury Grand Marquis was a full-size rear-wheel drive sedan sold by the Lincoln-Mercury division of the Ford Motor Company; the Grand Marquis was the flagship of the Mercury lineup. The nameplate itself had been in use since 1975 as the premium trim level of the Mercury Marquis; the Grand...
, and Lincoln Town Car
Lincoln Town Car
The Lincoln Town Car is a full-size luxury sedan that was sold by the upscale Lincoln division of Ford Motor Company; it was produced from 1981 to the 2011 model years...
) have always been FR, as was the Ford Mustang
Ford Mustang
The Ford Mustang is an automobile manufactured by the Ford Motor Company. It was initially based on the second generation North American Ford Falcon, a compact car. Introduced early on April 17, 1964, as a "1964½" model, the 1965 Mustang was the automaker's most successful launch since the Model A...
and Lincoln LS
Lincoln LS
The Lincoln LS is a mid-size, rear wheel drive sedan from Lincoln. For its production run from 1999 until 2006, it was based on the Ford DEW98 platform, which was shared with the Jaguar S-Type and Ford Thunderbird...
. In 2008 Hyundai
Hyundai Motor Company
Hyundai Motor Company is a Korean multinational automaker based in Seoul, South Korea which, along with Kia, comprises the Hyundai Kia Automotive Group, the world's fourth largest automaker as of 2009. As of 2011, it is the world's fastest growing automaker for two years running...
introduced its own rear-wheel drive car, the Hyundai Genesis
Hyundai Genesis
The Hyundai Genesis is a full-size luxury car initially introduced as a concept car in the 2007 New York International Auto Show. Hyundai has introduced the vehicle worldwide, known internally as the BH model, and markets the Genesis as a "premium sports sedan". The Genesis is currently not...
.
In Australia, FR cars have remained popular throughout this period, with the Holden Commodore
Holden Commodore
The Holden Commodore is an automobile manufactured since 1978 by the Holden subsidiary of General Motors in Australia, and, formerly, in New Zealand. In the mid-1970s, Holden established proposals to replace the long-serving Kingswood nameplate with a smaller, Opel-based model...
and Ford Falcon
Ford Falcon (Australia)
The Ford Falcon is a full-size car which has been manufactured by Ford Australia since 1960. Each model from the XA series of 1972 onward has been designed, developed and built in Australia and/or New Zealand, following the phasing out of the American Falcon of 1960–71 which had been re-engineered...
having consistently strong sales. In Europe, front-wheel drive was popularized by small cars like the Mini
Mini
The Mini is a small car that was made by the British Motor Corporation and its successors from 1959 until 2000. The original is considered a British icon of the 1960s, and its space-saving front-wheel-drive layout influenced a generation of car-makers...
, Renault 5
Renault 5
The Renault 5 was first unveiled on 10 December 1971, being launched at the beginning of 1972.The Renault 5 was styled by Michel Boué, who died before the car's release, the R5 featured a steeply sloping rear hatchback and front dashboard...
and Volkswagen Golf
Volkswagen Golf
The Volkswagen Golf is a small family car manufactured by Volkswagen since 1974 and marketed worldwide across six generations, in various body configurations and under various nameplates – as the Volkswagen Rabbit in the United States and Canada , and as the Volkswagen Caribe in Mexico .The...
and adopted for virtually all mainstream cars.
Upscale marques like Mercedes-Benz
Mercedes-Benz
Mercedes-Benz is a German manufacturer of automobiles, buses, coaches, and trucks. Mercedes-Benz is a division of its parent company, Daimler AG...
, BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
, and Jaguar remained mostly independent of this trend, and retained a lineup mostly or entirely made up of FR cars. Japanese mainstream marques such as Toyota and Nissan became mostly or entirely FF early on, while reserving for their latterly-conceived luxury divisions (Lexus
Lexus
is the luxury vehicle division of Japanese automaker Toyota Motor Corporation. First introduced in 1989 in the United States, Lexus is now sold globally and has become Japan's largest-selling make of premium cars. The Lexus marque is marketed in over 70 countries and territories worldwide, and has...
and Infiniti
Infiniti
is the luxury division of automaker Nissan. Infiniti officially started selling vehicles on November 8, 1989 in North America. Marketing operations have since grown to include the Middle East, South Korea, Russia, Taiwan, China, Ukraine and the United Kingdom. Infiniti began sales in additional...
, respectively) a mostly FR lineup. While many automakers lost sight of the true sports car, Mazda
Mazda
is a Japanese automotive manufacturer based in Fuchū, Aki District, Hiroshima Prefecture, Japan.In 2007, Mazda produced almost 1.3 million vehicles for global sales...
introduced the highly successful Miata roadster in 1990, a true 2-seater sports car using the traditional FR layout which led to other compaines such as General Motors to produce a FR sports car based on their Kappa
GM Kappa platform
Kappa was General Motors' subcompact rear-wheel drive automobile platform for roadster applications. The architecture debuted in the 2006 Pontiac Solstice and 2007 Saturn Sky, and ended production in 2009....
platform.
Currently most cars are FF, including virtually all front-engined economy cars, though FR cars are making a return as an alternative to large sport-utility vehicles. In North America, GM returned to production of the FR luxury car with the 2003 Cadillac CTS
Cadillac CTS
The Cadillac CTS is a mid-size car manufactured by the Cadillac marque of General Motors currently available in three body styles: Sedan, Coupe, and Sport Wagon. It was introduced in 2002 as a sports sedan, replacing the Cadillac Catera. The CTS and the supercharged CTS-V variant have been named...
, and with the removal of the DTS
Cadillac DTS
The Cadillac DTS is a full-size luxury sedan produced by General Motors, an American automobile company. The DTS replaced the Cadillac DeVille as General Motors' largest luxury car for the 2006 model year...
, Cadillac will be entirely FR (with four-wheel drive available as an option on several models) by 2010, and the 2010 Camaro returns as a FR sports car. Chrysler
Chrysler
Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....
returned its full-size cars to this layout with the Chrysler 300
Chrysler 300
The Chrysler 300 is a full-size upscale car first shown at the 2003 New York Auto Show as a concept car. Sales in the U.S. began in the spring of 2004 as an early 2005 model year car. Designed by Ralph Gilles, the new 300 was built as a high-end sedan while the SRT-8 model was designed to be the...
and related models. Ford never eliminated FR cars, but is looking to replace the dated designs that it currently has. Nissan are also bringing back the Silvia to their line-up, Mazda
Mazda
is a Japanese automotive manufacturer based in Fuchū, Aki District, Hiroshima Prefecture, Japan.In 2007, Mazda produced almost 1.3 million vehicles for global sales...
is said to be releasing a new rotary-powered FR car in their RX line-up by 2010 and there are rumours Toyota are bringing a successor to the AE86, in other words, an affordable RWD car. Hyundai
Hyundai
Hyundai ) is a global conglomerate company, part of the Korean chaebol, that was founded in South Korea by one of the most famous businessmen in Korean history: Chung Ju-yung...
introduced their affordable RWD car being the 2009 Hyundai Genesis
Hyundai Genesis
The Hyundai Genesis is a full-size luxury car initially introduced as a concept car in the 2007 New York International Auto Show. Hyundai has introduced the vehicle worldwide, known internally as the BH model, and markets the Genesis as a "premium sports sedan". The Genesis is currently not...
and 2010 Hyundai Genesis Coupe
Hyundai Genesis Coupe
The Hyundai Genesis Coupé is a rear-wheel drive sports coupe from Hyundai Motor Company, released on October 13, 2008 for the Korean market. It is Hyundai's first rear-wheel drive sports coupe, and shares its basic platform with the Hyundai Genesis luxury sedan....
In the 21st century, with solutions to the engineering complexities of 4WD being widely understood, and consumer demand for increasing performance in production cars, front-engined 4WD layouts are rapidly becoming more common, and most major manufacturers now offer 4WD options on at least some models. Manufacturers with a notable expertise and history in producing 4WD performance cars are Audi
Audi
Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....
and Subaru
Subaru
; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...
.