Rear suspension
Encyclopedia
For front-wheel drive
cars
, rear suspension has few constraints and a variety of beam axle
s and independent suspension
s are used.
For rear-wheel drive cars
, rear suspension has many constraints and the march to the superior but more expensive independent suspension
layout has been a long slog. The dynamics of such a vehicle are that the rear suspension must counteract by the tendency of the rolling wheel traveling in the opposite direction from the vehicle. This must be countered by the rear suspension taking up a counter-clockwise torque
; otherwise, the body and frame of the car will strip itself off the rear suspension, whatever it is. It is that need which dominates several of the varieties of rear suspension.
Henry Ford
's Model T used a torque tube
to restrain this force, for his differential
was attached to the chassis
by a lateral leaf spring
and two narrow rods. The torque tube surrounded the true driveshaft
and exerted the force to its ball joint
at the extreme rear of the transmission, which was attached to the engine. A similar method was used by the late-1930s Buick
and by Hudson's bathtub car of 1948, which used helical springs which could not take fore-and-aft thrust.
The Hotchkiss drive
, invented by Albert Hotchkiss, was the most popular rear suspension system used in American cars from the 1930s to the 1970s. The system uses longitudinal leaf springs attached both forward and behind the differential of the live axle
. These springs transmit the torque to the frame. Although scorned by many European car makers of the time, it was accepted by American car makers because it was inexpensive to manufacture. Also, the dynamic defects of this design were suppressed by the enormous weight of US passenger vehicles before implementation the Corporate Average Fuel Economy
standard.
Another Frenchman invented the De Dion tube
, which is sometimes called "semi-independent". Like a true independent rear suspension, this employs two universal joint
s or their equivalent from the center of the differential to each wheel. But the wheels cannot entirely rise and fall independently of each other; they are tied by a yoke that goes around the differential, below and behind it. This method has had little use in the United States
, though it does not evidence the Bump Steer
that a more expensive, true independent suspension does. Its use around 1900 was probably due to the poor quality of {tires|tyres}, which wore out quickly. By removing a good deal of unsprung weight
, as independent rear suspensions do, it made them last longer.
Rear wheel drive vehicles today frequently use a fairly complex fully independent, multi-link suspension
to locate the rear wheels securely while providing decent ride quality
.
Front-wheel drive
Front-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...
cars
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
, rear suspension has few constraints and a variety of beam axle
Beam axle
A beam axle is a suspension system, also called a solid axle, in which one set of wheels is connected laterally by a single beam or shaft...
s and independent suspension
Independent suspension
Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically independently of each other. This is contrasted with a beam axle, live axle or deDion axle system in which the wheels are linked – movement on one side affects...
s are used.
For rear-wheel drive cars
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
, rear suspension has many constraints and the march to the superior but more expensive independent suspension
Independent suspension
Independent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically independently of each other. This is contrasted with a beam axle, live axle or deDion axle system in which the wheels are linked – movement on one side affects...
layout has been a long slog. The dynamics of such a vehicle are that the rear suspension must counteract by the tendency of the rolling wheel traveling in the opposite direction from the vehicle. This must be countered by the rear suspension taking up a counter-clockwise torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
; otherwise, the body and frame of the car will strip itself off the rear suspension, whatever it is. It is that need which dominates several of the varieties of rear suspension.
Henry Ford
Henry Ford
Henry Ford was an American industrialist, the founder of the Ford Motor Company, and sponsor of the development of the assembly line technique of mass production. His introduction of the Model T automobile revolutionized transportation and American industry...
's Model T used a torque tube
Torque tube
A torque tube system is a driveshaft technology, often used in automobiles with a front engine and rear drive. It is not as widespread as the Hotchkiss drive, but is still occasionally used to this day...
to restrain this force, for his 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...
was attached to the chassis
Chassis
A chassis consists of an internal framework that supports a man-made object. It is analogous to an animal's skeleton. An example of a chassis is the underpart of a motor vehicle, consisting of the frame with the wheels and machinery.- Vehicles :In the case of vehicles, the term chassis means the...
by a lateral leaf spring
Leaf spring
Originally called laminated or carriage spring, a leaf spring is a simple form of spring, commonly used for the suspension in wheeled vehicles...
and two narrow rods. The torque tube surrounded the true 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...
and exerted the force to its ball joint
Ball joint
In an automobile, ball joints are spherical bearings that connect the control arms to the steering knuckles.More specifically, a ball joint is a steel bearing stud and socket enclosed in a steel casing. The bearing stud is tapered and threaded. It fits into a tapered hole in the steering knuckle. A...
at the extreme rear of the transmission, which was attached to the engine. A similar method was used by the late-1930s Buick
Buick
Buick is a premium brand of General Motors . Buick models are sold in the United States, Canada, Mexico, China, Taiwan, and Israel, with China being its largest market. Buick holds the distinction as the oldest active American make...
and by Hudson's bathtub car of 1948, which used helical springs which could not take fore-and-aft thrust.
The Hotchkiss drive
Hotchkiss drive
The Hotchkiss drive is a system of power transmission. It was the dominant form of power transmission for front-engine, rear-wheel drive layout cars in the 20th century...
, invented by Albert Hotchkiss, was the most popular rear suspension system used in American cars from the 1930s to the 1970s. The system uses longitudinal leaf springs attached both forward and behind the differential of the live axle
Live axle
A live axle, sometimes called a solid axle, is a type of beam axle suspension system that uses the driveshafts that transmit power to the wheels to connect the wheels laterally so that they move together as a unit....
. These springs transmit the torque to the frame. Although scorned by many European car makers of the time, it was accepted by American car makers because it was inexpensive to manufacture. Also, the dynamic defects of this design were suppressed by the enormous weight of US passenger vehicles before implementation the Corporate Average Fuel Economy
Corporate Average Fuel Economy
The Corporate Average Fuel Economy are regulations in the United States, first enacted by the U.S. Congress in 1975, and intended to improve the average fuel economy of cars and light trucks sold in the US in the wake of the 1973 Arab Oil Embargo...
standard.
Another Frenchman invented the De Dion tube
De Dion tube
A de Dion tube is an automobile suspension technology. It is a sophisticated form of non-independent suspension and is a considerable improvement over the alternative swing axle and Hotchkiss drive types. A de Dion suspension uses universal joints at both the wheel hubs and differential, and uses a...
, which is sometimes called "semi-independent". Like a true independent rear suspension, this employs two universal joint
Universal joint
A 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 or their equivalent from the center of the differential to each wheel. But the wheels cannot entirely rise and fall independently of each other; they are tied by a yoke that goes around the differential, below and behind it. This method has had little use in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, though it does not evidence the Bump Steer
Bump Steer
Bump steer is the term for the tendency of a wheel to steer as it moves upwards into jounce. It is typically measured in degrees per metre or degrees per foot....
that a more expensive, true independent suspension does. Its use around 1900 was probably due to the poor quality of {tires|tyres}, which wore out quickly. By removing a good deal of unsprung weight
Unsprung weight
In a ground vehicle with a suspension, the unsprung weight is the mass of the suspension, wheels or tracks , and other components directly connected to them, rather than supported by the suspension...
, as independent rear suspensions do, it made them last longer.
Rear wheel drive vehicles today frequently use a fairly complex fully independent, multi-link suspension
Multi-link suspension
A multi-link suspension is a type of vehicle suspension design typically used in independent suspensions, using three or more lateral arms, and one or more longitudinal arms....
to locate the rear wheels securely while providing decent ride quality
Ride quality
Ride quality refers to the degree of protection offered vehicle occupants from uneven elements in the road surface, or the terrain if driving off-road. A car with very good ride quality is also a comfortable car to ride in. Cars which disturb vehicle occupants with major or minor road...
.