On a vehicle

Vehicle

A vehicle is a device that is designed or used to transport people or cargo. Most often vehicles are manufactured, such as bicycles, cars, motorcycles, trains, ships, boats, and aircraft....

, a gaiter or boot refers to a protective flexible sleeve covering a moving part, intended to keep the part clean.

On motorcycles and bicycles

Gaiters are pleated rubber tubes enclosing the front suspension tubes

Motorcycle fork

A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a pair of triple clamps. It typically incorporates the front suspension and front brake, and allows the bike to be steered via handlebars attached to the top clamp....

 of some 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 mountain bike

Mountain bike

A mountain bike or mountain bicycle is a bicycle created for off-road cycling. This activity includes traversing of rocks and washouts, and steep declines,...

s with telescopic front forks. Gaiters protect the sliding parts of the front suspension

Suspension (motorcycle)

A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, and providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise, bumps and vibrations....

 from dirt and water.

On cars and other vehicles

Similar gaiters to those described above find multiple uses on most vehicles. They are used at both ends of 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...

s, protecting constant-velocity joint

Constant-velocity joint

Constant-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 from the ingress of dirt, and retaining the grease. They also prevent the ingress of dirt where one component slides within another, for example, on suspension

Suspension (vehicle)

Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...

 struts or the ends of steering

Steering

Steering is the term applied to the collection of components, linkages, etc. which will allow a vessel or vehicle to follow the desired course...

 racks. Finally, they are also usually used to perform the same function on 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...

s, which appear on suspension wishbone

Wishbone

Wishbone may refer to:* The wishbone, a Y-shaped bone found in birds* Wishbone suspension, an automobile suspension design.* Wishbone , an children's educational television show...

s and steering tie rod

Tie rod

A tie rod is a slender structural unit used as a tie and capable of carrying tensile loads only.- Subtypes and examples of applications :* In airplane structures, tie rods are sometimes used in the fuselage or wings....

ends.