The impossible wheel, also known as the BC wheel (after the comic strip B.C.), represents the most basic type of
unicycle
A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a bicycle frame, frame with a bicycle saddle, saddle, and has a human-powered vehicle, pedal-driven direct-drive mechanism, direct-drive. A two spee ...
, consisting of a single, spoked
wheel
A wheel is a circular component that is intended to rotate on an axle Bearing (mechanical), bearing. The wheel is one of the key components of the wheel and axle which is one of the Simple machine, six simple machines. Wheels, in conjunction wi ...
with pegs extending from the
axle
An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearing ...
. The rider mounts the wheel by jumping onto the pegs while in motion or by putting one foot onto one plate or peg and pushing along like a skateboard.
This device has no drivetrain, so when forward inertia runs out due to gravity and friction, the ride ends. Newer BC wheels use plates which hang below the axle instead of pegs in line with the axle. This makes them easier to ride since the center of gravity is lower.
The unicycling community favors the term ''BC wheel'' because the device is not actually impossible to ride; proficiency can be gained with a few hours of practice. Tricks, such as hopping, drops,
grinds
In Ireland, grinds are private tuition; a major industry in Ireland, particularly at secondary school level.
In 2012, the Office of the Revenue Commissioners launched an investigation into a perceived failure of some teachers to declare extra ...
, and spins, are possible.
Ultimate wheel
An ultimate wheel is a wheel with two pedals directly connected – similar to a
unicycle
A unicycle is a vehicle that touches the ground with only one wheel. The most common variation has a bicycle frame, frame with a bicycle saddle, saddle, and has a human-powered vehicle, pedal-driven direct-drive mechanism, direct-drive. A two spee ...
and impossible wheel. It has no seat or frame but offset and functional pedals. There are several different designs: the most popular involves a solid or semi-solid disk inside a regular small bicycle wheel rim with the pedals attached directly to the disk. A less common style uses metal cross braces instead of wood.
Some mounting and riding techniques include:
* Regular mount – have one pedal lower than the other and step up to the other pedal
* Free jump mount – release the wheel then jump onto the pedals
* Standard riding – simply being able to ride without falling off
* Turning – turning by twisting your body and the wheel
*
Bunny hop The bunny hop is a novelty dance created at Balboa High School in San Francisco in 1952.Monowheel