This FAQ is a brief overview to some of the different types of bicycles available.
Bicycle Moto Cross (BMX) bicycles are designed for rough off road riding and are typically single speed. People also use them for stunt riding, and you may see some fitted with stunt pegs.
Mountain Bike (MTB)
A mountain bike is designed for trail riding and downhill riding. It can also be ridden on the road. They come in many shapes and forms. Some have no suspension, whilst others have front and rear suspension. A mountain bike without rear suspension is usually called a hard tail bike.
Most MTBs use 26 inch wheels which is the standard. This size wheel is fairly strong, especially when coupled with the large off road tyres that are fitted to MTBs.
An MTB is suited for off road riding and will handle rough terrain quite easy. It is very stable on rough terrain, but is a lot slower to ride on the road when compared to a road bike. It is also suitably geared for climbing hills.
Another style of bike that has a similar riding position to a mountain bike, but better road speed is a Hybrid bicycle. Hybrids are a cross between a mountain bike and a road bike. They have an upright comfortable position, road tyres, and are usually a lot lighter than a mountain bike.
Hybrid bicycles are typically used for commuting.
A touring bicycle is designed for loaded cycle touring and has the capability to be fitted with mudguards, racks, panniers and extra water cages. They are typically fitted with wider road type tyres that are suitable for gravel riding also.
They usually come with a stronger frame and longer chainstays so that the back of your feet don't hit the rear panniers. They are usually fitted with a relaxed drop bar style handlebar. The geometry of the frame is also different and allows for much more easier steering and handling when loaded.
As above for touring, but usually fitted with Trekking bars and MTB gear and is designed for extreme off road conditions.
Randonneur or 'All Rounder'
A rare beast in Australia where we like to specialise. 'Randonneur' is a French term, coined to describe a bike that can do a bit of everything - you can ride with the pack or take a doddle with the kids, you can ride light or carry a load, you'd use it to visit Gran on Sunday then pick up some groceries on the way home. They are the 'family station wagon' of cycling. However, like any Jack of All Trades, they do everything well but the specialists do it better. They can carry a load but not like a heavy tourer. They are fast but heavier than a racer and with more comfortable geometry. They have wider wheels and tyres to ride on rough roads but wont handle true off road work.
Typically, they look like any other racing or flat bar road bike ... until you look at the details. Most randonneurs start life as a touring bike or hybrid, and are then modified by the owner over time to reflect how they are used.
Road Racing Bicycle
A bicycle designed to provide the fastest ride possible on sealed surfaces while conforming to the rules of the Union Cycliste Internationale (UCI). Their design facilitates high performance riding providing a good aerodynamic position to minimise the effort required at a given speed. They are also designed to permit the rider to ride in close formation with other cyclists, for protection from the wind.
Triathlete Racing Bicycle
Similar to a Road Racing Bicycle and not constrained by the UCI rules, a Triathlete Bicycle provides better aerodynamics than the Road Racing Bicycle while sacrificing some maneuverability and ability to climb hills as most Triathlete courses are generally flat. Triathlete bicycles are also designed to cater for the riders legs being transitioned to a run.
A track bicycle is intended for velodrome riding events and compared to a road bicycle has no brakes, a fixed wheel, usually a high gear ratio and higher (steeper) seat position and higher bottom brackets with dropouts facing backwards. The UCI set limits defining geometry and design. The higher the gear ratio, the slower the rate of acceleration that is possible and the higher the top speed. The fixed gear means that there is no freewheel, the pedals / cranks continue to revolve while the bike is in motion and braking is possible only slowly - stopping pedaling and pushing against the pedals.
Fixed Wheel Bicycle
Essentially a track bike however can also be a road bike or other styles of bikes. The modern fixed wheel bike is intended for city and urban cycling. The rear wheel is fixed (see track bike). Fixed wheel cycling is currently a popular trend in cycling, in particular with bike messengers. Due to the popularity many top bike brands currently have fixed wheel (and fixed wheel / single speeds with flip flop hub) on the market.
Single Speed Bicycle
A single speed bike has no gears and is limited to one front chain ring and one rear cog. The rear cog is a freewheel allowing the rider to pedal forward and to stop pedaling while the momentum continues. Single speed bicycles offer lower maintenance compared with geared bicycles and while being limited to one single gear ratio. Many simple holland bikes and childrens bikes are essentially single speed.
Tag-along Kid's Bikes
Essentially half a bicycle that attaches to the rear of the parent's bicycle. The child can pedal the bike but can not balance or steer the bike. They come in a variety of types, some single speed, some with gears. They are useful for the child who can not ride or is too young to endure the longer distances that adults ride.
A BOB (Beast of Burden) trailer is a single wheeled trailer that attaches to the bike's rear axle with a swing arm. It faithfully follows the bike everywhere. Being a single wheel trailer it places half of the load's weight on the rear wheel of the bike, and the rest on the trailer's wheel.
BOB trailers are usually used by cycle tourists, but are used by other cyclists as well. They can carry a load up to 32 kgs (recommended) and come in several models. One model has suspension for off road riding.
They usually come with a dry sak bag and a flag to aid in visibility.