A unicycle has one wheel. The prefix “uni” means one, and that single wheel is the defining feature that separates it from every other human-powered vehicle. But that one wheel supports a surprisingly diverse machine, and there’s more to the story than the simple answer suggests.
What Makes Up That Single Wheel
A unicycle’s wheel is built from the same basic components as a bicycle wheel: a hub at the center, spokes radiating outward, a metal rim, an inner tube, and a tire. The key difference is that the hub connects directly to the crank arms (the metal bars your feet push on), with no chain or gears in between. When you pedal forward, the wheel turns forward. When you stop pedaling, the wheel stops. This direct connection is what makes riding a unicycle so physically demanding and why balance is entirely up to the rider.
The rest of the machine is minimal. A fork-shaped frame sits above the wheel, holding a seat post and saddle. Pedals attach to the crank arms on either side of the hub. Some unicycles include a brake, but many don’t. That’s the entire vehicle: one wheel, one seat, two pedals, no handlebars.
Wheel Size Changes Everything
Not all unicycle wheels are the same diameter, and the size you choose determines what the unicycle can do. Trials unicycles, built for jumping and technical tricks, typically use a 20-inch wheel. Mountain unicycles (often called munis) step up to 24-inch or 26-inch wheels with fat, knobby tires around 3 inches wide for grip on rough terrain. Touring unicycles designed for long-distance riding use 29-inch or 36-inch wheels, which cover more ground per pedal revolution.
Crank arm length varies with the discipline too. A 20-inch trials unicycle pairs well with cranks around 145 millimeters long for quick, responsive control. Mountain unicycles often use 150 to 170 millimeter cranks, giving riders more leverage on steep hills. Shorter cranks on larger wheels let distance riders maintain higher speeds with less effort, which is how record-setting riders cover enormous distances on 36-inch unicycles.
Multi-Wheel Unicycles Exist (Sort Of)
Here’s where things get interesting. Some unicycles stack two or more wheels vertically on top of each other, with friction between the tires transmitting power from one wheel to the next. These are still technically unicycles because only one wheel touches the ground at any time. The extra wheels spin against each other in opposite directions, creating a tall, visually striking machine.
Riding a two-wheeled stacked unicycle is one of the hardest variations because the rider’s pedaling reflexes have to be completely reversed. Since the power passes through an even number of wheels, pushing the pedals forward actually drives the bottom wheel backward. An odd number of stacked wheels gives normal steering. Multi-wheeled giraffe unicycles, some built with many wheels extending from the pedals all the way up to the seat, were famously constructed by Mr. Tsukahara of Nagoya, Japan in 1980. They’re essentially performance pieces, with all those wheels spinning in alternating directions as the rider pedals.
Electric Unicycles: Still One Wheel
Electric unicycles, or EUCs, are a modern reinvention of the concept. They keep the single-wheel design but replace pedaling with a battery-powered motor. Instead of crank arms and pedals, riders stand on foot platforms on either side of the wheel and lean forward to accelerate. Gyroscopic sensors detect the rider’s weight shift and adjust the motor to maintain balance, making the learning curve very different from a traditional unicycle.
Despite the technology inside, the core principle remains the same: one wheel, one rider, no handlebars. The gyro-assisted balance is the biggest departure from the manual version, where staying upright depends entirely on constant micro-adjustments through the pedals.
What One Wheel Can Actually Do
The single wheel might seem like a limitation, but competitive unicyclists push it remarkably far. In January 2025, Ken Looi of New Zealand rode 455.235 kilometers in 24 hours on a 36-inch unicycle, a distance that would challenge many cyclists. Lisanne Boer of the Netherlands set the women’s record in June 2025 at 412.147 kilometers over the same time frame. Both riders used 100-millimeter cranks, prioritizing speed and efficiency over control.
Beyond distance records, unicycles are used for mountain trail riding, basketball, hockey, and freestyle routines that resemble figure skating. All on one wheel.