dirt bike with a
paddle tire Off-road motorcycles, also known as
adventure bikes,
dirt bikes or
scramblers, are specially designed for
off-road use. The term off-road refers to driving surfaces that are not conventionally paved. These are rough surfaces, often created naturally, such as sand, gravel, a river, mud or snow. These types of terrain can sometimes only be travelled on with
vehicles designed for off-road driving (such as
SUVs,
ATVs,
snowmobiles and
mountain bikes in recent decades, and
minibikes even earlier) or vehicles are designed to better handle off-road conditions. Compared to road-going motorcycles, off-road machines are lighter and more flexible, typically have
long travel suspension, high ground clearance, and are geared higher to provide more torque in off-road situations. Wheels (usually 21" front, 18" rear) have
knobby tires, often clamped to the rim with a
rim lock. Many competitive events have emerged and developed into a variety of off-road
motorcycle sports, for which a number of specialized motorcycles have been built: •
Motocross - Such bikes are raced on short, closed off-road tracks with a variety of obstacles. The motorcycles have a small fuel tank for lightness and compactness. Long-travel suspension allows riders to take jumps at high speed. Motocross engines are single-cylinder
two-stroke or
four-stroke units, which vary in size from 50cc up to about 500cc. At the professional level, bikes are split up into two levels based on their displacements:
MX and
MX Lite. The MX Lite class contains 125cc two-stroke
engines and 250cc four-stroke engines, while the MX class pits 250cc two-stroke engines against 450cc four-stroke engines. The actual displacement for both four-strokes and two-strokes can be under what is listed for the different bikes. The differences in power,
displacement, torque, and weight are all variables that balance the competition between two-stroke and four-stroke engines. Motocross sidecar outfits have bigger engines, usually four-stroke and often twin-cylinder. Motocross bikes are also used in
freestyle motocross. •
Trials - A specialized form of off-road competition testing balancing skills and precision rather than speed. For a trials bike, low weight and crisp throttle response power are prioritized, so trials bikes tend to have a small (125 cc to 300 cc) engine, with two-strokes being common. During the trial, the rider stands on the foot-pegs, so a trials bike will have only a vestigial seat, or no seat at all. Fuel tanks are very small, giving a very limited range. Trials bikes are designed to tackle obstacles which would be impossible for other kinds of motorcycle. •
Enduro - A modified and road-legal motocross bike which is something between a Trial motorcycle and Motocross, having the addition of a horn, lights, effective silencing and a number plate. Enduro riders compete over a longer course (which may include roads); and an enduro event may last between one day and six days (such as the
International Six Days Enduro). Some enduro events (known as "multi-lappers") are held on rather shorter circuits, not unlike
scramble tracks. "Multi-lappers" are especially popular with novice riders. •
Hard Enduro–Enduro bike with more focus on durability, lighter weight, agility and low-end torque. •
Rally raid, or "rallies"—A special type of enduro bike with a significantly larger fuel tank for very long distance racing, typically through deserts (e.g.
Paris-Dakar rally). Engine capacities tend to be larger, usually between 450 cc and 750 cc. •
Hill Climb–Longer wheelbase to prevent
backflip,
paddle or spiked tyres. Unlike the small screws/studs found on snow tyres, each spike is 4cm long and 1cm thick, bolted on with two washers on interior and exterior of tyre. 1, 2 or 3 in a row, spaced equidistantly around the circumference of a tyre. •
Dual-Sport—A dual-sport bike is a multi-purpose bike, made for on-road and recreational off-road riding. A dual-sport bike may resemble an enduro bike, but since a dual-sport bike is not intended to be used for competition, it may be less rugged, and equipped with dual-purpose tires and with more road legal equipment, such as indicators, mirrors and extra instruments. Most dual-sport bikes require a number plate to be ridden on state and county roads. •
Track racing—High-speed oval racing, typically with no brakes, nor rear suspension. The engines, fueled by methanol, are long-stroke four-stroke singles, such as
JAP and
Jawa. They have at most two gears. Some types, such as speedway, and grass-track bikes, are designed to take left turns only. • Snow bikes—A snow bike takes a typical dirt-bike and replaces the rear wheel with a single tread system similar to a
snowmobile and the front wheel with a large ski. They are much smaller and more nimble than a snowmobile, and they have a tighter turning radius, which lets the rider go where many snowmobiles cannot. The first prototype of motorcycles with a rear tread date all the way back to the 1920s, with failed attempts to bring them onto the market until recent times. Many motorcycles made after the 1990s or later can be fitted with a kit that transforms them into a snow bike. == Dual-purpose ==