Downhill bike

A downhill bike (also known as a downhill mountain bike) is a full suspension bicycle designed for downhill cycling 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 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.

Geometry
These bikes will also have very slack head tube angles (63 degrees or less), long wheelbases (over 45 in), and will accommodate the use of up to 2.5 in width knobbed tires. Downhill frames are also overbuilt to handle the stress of riding over rocky terrain, drops, and jumps. Bike weights have been typically over 34 lb, but modern downhill bikes have broken the 30 lb weight barrier (with some custom builds on carbon frames weighing between 27 - 29 lb). Some newer (2014/5) downhill bikes can be built to weigh under 30 lb, such as the Trek Session 9.9 or Kona Supreme Operator. Dual crown e-bikes typically weigh 25 - 35 kg.

Adjustable head tube angles are also available to adapt the bike to the owner's preferred style of riding.

Suspension
Will typically have 7 - 10 in of rear suspension travel, and be designed around a 7 - 8 in suspension fork. The suspension sag 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 standard, which uses a 1.5 in wide steerer tube, instead of the more conventional 1.125 in diameter, for added stiffness and strength. Most downhill bikes use dual crown forks which allow longer travel at the front(usually 203 mm 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, 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 or carbon fiber. Some manufacturers have started using 3d printed "lugs" for a more personalized geometry.