A downhill bike (also known as a downhill

mountain bike A mountain bike (MTB) or mountain bicycle is a bicycle designed for off-road cycling. Mountain bikes share some similarities with other bicycles, but incorporate features designed to enhance durability and performance in rough terrain, which ...

) is a full suspension

bicycle A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist. Bic ...

designed for

downhill cycling Downhill mountain biking (DH) is a style of mountain biking practiced on steep, rough terrain that often features Glossary of cycling#gap jump, jumps, Glossary of cycling#drop, drops, Glossary of cycling#rock garden, rock gardens and other obst ...

on particularly steep, technical trails. Unlike a typical mountain bike, durability and stability are the most important design features, compared to lighter, more versatile

cross-country Cross country or cross-country may refer to: Places * Cross Country, Baltimore, a neighborhood in northwest Baltimore, Maryland * Cross County Parkway, an east–west parkway in Westchester County, NY * Cross County Shopping Center, a mall in Yo ...

bikes. Downhill bikes are primarily intended for high-speed descent, and downhill riders will usually push, or shuttle via chairlifts or motorized vehicles, to the trailhead. Downhill bikes share similarities with freeride bikes due to their large strong frames and increased travel.

History

Geometry

These bikes will also have very slack head tube angles (63 degrees or less), long wheelbases (over ), and will accommodate the use of up to width knobbed tires. Downhill frames are also overbuilt to handle the stress of riding over rocky terrain,

drops Drop, DROP, drops or DROPS may refer to: * Drop (liquid) or droplet, a small volume of liquid ** Eye drops, saline (sometimes mydriatic) drops used as medication for the eyes * Drop (unit), a unit of measure of volume * Falling (physics), allowi ...

, and

jumps Jumping or leaping is a form of locomotion or movement in which an organism or non-living (e.g., robotic) mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and o ...

. Bike weights have been typically over , but modern downhill bikes have broken the weight barrier (with some custom builds on carbon frames weighing between 27-29 pounds) Some newer (2014/5) downhill bikes can be built to weigh under , such as the Trek Session 9.9 or Kona Supreme Operator. Dual crown e-bikes typically weigh 25-35kg. Adjustable head tube angles are also available to adapt the bike to the owner's preferred style of riding.

Components

Suspension

Will typically have of rear suspension travel, and be designed around a suspension

fork In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tines with which one can spear foods ei ...

. The suspension

sag SAG, SAg, or sag may refer to: Land formations * Sag (geology), or ''trough'', a depressed, persistent, low area * Sag pond, a body of water collected in the lowest parts of a depression People * Ivan Sag (1949–2013), American linguist ...

is also much higher than cross-country bikes (25%-50% of total travel vs. 10%-20%) for a more supple ride at higher speeds.

Fork

Other innovations include the use of OnePointFive

head tube The head tube is the part of a cycle's tubular frame within which the front fork steerer tube is mounted. On a motorcycle, the "head tube" is normally called the steering head. On bicycles the manufacturer's brand located on the head tube is kno ...

standard, which uses a wide steerer tube, instead of the more conventional diameter, for added stiffness and strength. Most downhill bikes use dual crown forks which allow longer travel at the front(usually and increased stiffness that a single crown fork cannot offer. Drawbacks though, are increased weight and reduced turning radius.

Brakes

Downhill bikes usually have hydraulic, quad piston

disc brakes A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hol ...

, and the discs may be 200 mm or larger. Brake discs and calipers may come with finned heatsinks for better heat dissipation.

Drivetrain

Downhill bikes usually have a chain guide to prevent accidental chain derailment. Some manufacturers are experimenting with internal gearboxes for improved reliability. Cassettes will usually only contain a few small sprockets instead of the 12 sprockets found on other types of mountain bikes.

Tires

Downhill bikes need very strong tires and wheels. The standard wheel size for downhill bikes is 27.5, but with recent changes to UCI World Cup Downhill rules, some brands are experimenting with 29" and "mullet" 29" cross 27.5" downhill bikes. Tires are usually 2.5-2.6" wide, plus tires are 2.8-3.0". Plus tires are only used in recreational riding, not competition.

Materials

Downhill bikes are typically made of steel,

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...

carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...

. Some manufacturers have started using 3d printed "lugs" for a more personalized geometry.

References

External links

"A Brief History of the Mountain Bike"
by

Jobst Brandt Jobst Brandt (January 14, 1935 – May 5, 2015) was an American mechanical engineer, inventor, bicycle enthusiast, educator, and author. Early life Brandt was born in New York City, where his father, the German-born agricultural economist Karl Br ...

{{Human-powered vehicles Cycle types Mountain biking Cycle sport