Fender is the US English term for the part of an automobile, motorcycle or other vehicle body that frames a wheel well. Its primary purpose is to prevent sand, mud, rocks, and liquids from being thrown into the air by the rotating tire. Fenders are typically rigid and can be damaged by contact with the road surface. Instead flexible mud flaps are used close to the ground where contact may be possible.
Sticky materials such as mud may adhere to the smooth outer tire surface, while smooth loose objects such as stones can become temporarily embedded in the tread grooves as the tire rolls over the ground. These materials can be ejected from the surface of the tire at high velocity as the tire imparts kinetic energy to the attached objects. For a vehicle moving forward, the top of the tire is rotating upward and forward, and can throw objects into the air at other vehicles or pedestrians in front of the vehicle.
In British English, the fender is called the wing (usually only refers to the panels over the front wheel arches, in modern cars, since the rear 'fenders' are more an integral part of the car's body shape). The equivalent component of a bicycle or motorcycle, or the "cycle wing" style of wing fitted to vintage cars which is not integral with the bodywork, is called a mudguard in Britain, as it guards other road users - and in the case of a bicycle or motorcycle, the rider as well - from mud, and spray, thrown up by the wheels.
In the United States, a minor car accident is often called a "fender bender".
Trucks and automobiles Edit
Most passenger automobiles have four fenders, one over each wheel. For vehicles with a narrow car body that exposes the tire, the fender is an exposed curve over the top of the tire. For wide body vehicles that cover the tire, the fender forms the wheel well surrounding the tire, and is not directly visible from above the car body.
Wheel wells tend to be much larger than the diameter of the tire, because they do not move with the tire suspension and consequently must be large enough to allow the full range of tire motion on the suspension without touching the interior of the wheel well. More elaborate designs include fender skirts for enclosing the outside edge of the wheel well, and stylized pontoon fenders for exposed fenders.
Certain types of cars with narrow bodies, such as the Lotus Seven, Allard, and Caterham Seven, use what are called cycle fenders in the US or cycle wings in Britain, for their resemblance to those used on bicycles. They are attached to the wheel suspension and remain at a fixed distance from the tire regardless of wheel motion, and can therefore be much closer to the tire than fixed wheel wells. This was popular on early Classic Trials cars because the fenders were lightweight and allowed for a thin streamlined body. They persist on cars wanting a "vintage" look.
Bicycles and motorcyclesEdit
There are generic fenders for bicycles that can be fitted to most bicycle frames. These catch and redirect road spray thrown up by the tires, allowing the rider to remain relatively clean. They are relatively uncommon on bicycles in the more car dependent English-speaking countries, as bikes in these countries tend to be sports-oriented, with minimal clearance between tires and frame tubes for fenders, or are only ridden in clement conditions, although there are a few fenders that are designed to be attached to the seat post. However, European utility bicycles, traditional roadsters used in developing countries, serious touring bicycles, and beach cruisers are nearly always fitted with fenders, universally known in British English as mudguards. They are also fitted to motorcycles.
In the UK it is a legal requirement that a motorcycle should be fitted with mudguards. While motorcycles are invariably fitted with mudguards, only touring cycles generally have fully functional mudguards. Some machines can be seen with a stub of a mudguard only a few inches long, which satisfies the legal requirements but does not actually provide any protection from thrown mud and spray.
Sporty-styled or racing motorcycles sometimes come with, or have added as an aftermarket accessory, a "hugger" rear fender, attached to the rear swingarm and very close to the tire, rather than attached to the rear subframe and away from the tire. Conversely, the practice of removing the front fender and reducing the size of the rear fender produced the bobber customization style of the 1950's onwards.