Drive wheel

drive wheel is a wheel of a motor vehicle that transmits force, transforming torque into tractive force from the tires to the road, causing the vehicle to move. The powertrain delivers enough torque to the wheel to overcome stationary forces, resulting in the vehicle moving forwards or backwards.[1][2]

A two-wheel drive vehicle has two driven wheels, typically both at the front or back, while a four-wheel drive has four.

A steering wheel is a wheel that turns to change the direction of a vehicle. A trailer wheel is one that is neither a drive wheel, nor a steer wheel. Front-wheel drive vehicles typically have the rear wheels as trailer wheels.

The rear driven wheels of a racing car throwing gravel

Differentials and drive shafts deliver torque to the front and rear wheels of a four-wheel drive truck

Drive wheel configurations

Front-wheel drive

Front-wheel drive (FWD) vehicles’ engines drive the front wheels. Using the front wheels for delivery of power as well as steering allows the driving force to act in the same direction as the wheel is pointing.[3] This layout is commonly used in modern passenger cars.

Opperman Motocart

A rare example of front wheel drive was the Opperman Motocart. This slow-speed agricultural and light freight vehicle was a tricycle with the front wheel carrying a large tractor tyre. The wheel was powered by a small single cylinder Douglas engine carried on the front mono fork that formed the steering gear.

Rear-wheel drive

Rear-wheel drive (RWD) typically places the engine in the front of the vehicle, with a driveshaft running the length of the vehicle to the differential transmission. However, mid engine and rear engine layouts can also used.

It was a common layout used in automobiles throughout the 20th century. At this time, FWD designs were not practical due to complexity (in FWD, engine power and steering must both be combined in the front axle).

Rear-wheel Two-wheel Four-wheel Six-wheel Eight-wheel Twelve-wheel

Two-wheel drive

For four-wheeled vehicles, two-wheel drive describes vehicles that transmit torque to at most two road wheels, referred to as either front- or rear-wheel drive. The term 4×2 is also used, to indicate four total road-wheels with two being driven.

For vehicles that have partial four-wheel drive, the term two-wheel drive refers to the mode when four-wheel drive is deactivated and torque is applied to only two wheels.

All-wheel drive

Four-wheel drive

This configuration allows all four road wheels to receive torque from the power plant simultaneously. It is often used in rally racing on mostly paved roads.

Four-wheel drive is common in off-road vehicles because powering all four wheels provides better control on loose and slippery surfaces. Four-wheel drive manufacturers have different systems such as “High Range 4WD” and “Low Range 4WD”. These systems may provide added features such as a varying of torque distribution between axles or varying gear ratios.[4]

Common terms for this configuration include four-wheel drive, 4WD, 4×4 (pronounced “four-by-four”), and all-wheel drive (AWD).

Six-wheel drive

Eight-wheel drive

Twelve-wheel drive

Notes

  1. “Driving wheel”. thefreedictionary.com. Retrieved 13 July 2013any wheel of a vehicle that transforms torque into a tractive force.
  2. Russ, Carey. “Driving Wheels: Introduction and Rear-Wheel Drive”. The Auto Channel. Retrieved 13 July 2013.
  3. Hillier, V.A.W.; Coombes, Peter (2004). Hilliers Fundamentals of Motor Vehicle Technology (Fifth ed.). Nelson Thornes. p. 263. ISBN 9780748780822. Retrieved 13 June2013.
  4. “Jeep.ca”. www.jeep.ca. Retrieved 2016-07-25.
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Constant-velocity joint Constant-velocity joints (also known as homokinetic or CV 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 vehicles, and many modern rear wheel drive cars with independent rear suspension typically use CV joints at the ends of the rear axle halfshafts and increasingly use them on the drive shafts. Constant-velocity joints are protected by a rubber boot, a CV gaiter, usually filled with molybdenum disulfide grease. Cracks and splits in the boot will allow contaminants in, which would cause the joint to wear quickly as grease leaks out. This way the friction parts don’t get proper lubrication and get damaged due to minor particles that get in, while water causes metal components to rust and corrode. Wear of the boot often takes the form of small cracks, which appear closer to the wheel,  because it is the wheel that produces vibration and ...
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