Types of Bicycle: Purpose Shapes Form

Purpose shapes form

Walk into a bike shop for the first time and almost everyone feels the same bewilderment. Every bike has two wheels, pedals and a handlebar, yet prices range from a few hundred thousand to tens of millions of KRW, and they look subtly or dramatically different. Some have handlebars that curve downward like a pair of horns; others have tires as thick as an adult's fist. On some, the saddle sits almost on the frame; others come with a backrest like a chair.

This diversity isn't a matter of fashion or decoration. Because a bicycle runs on a very small power source, human muscle, its design changes completely depending on where that small amount of power is spent. If you want to ride at 40 km/h on smooth asphalt, you have to stake everything on cutting air resistance and weight; if you want to descend a rocky mountain trail, absorbing impacts and staying stable enough not to crash matter above all. A bike for carrying children to the market needs load capacity and a low center of gravity more than speed. In the end, the question “Where are you riding, and what for?” determines the shape of the bicycle.

In this chapter we divide today's common bicycles into four broad families: the road family, pursuing speed and efficiency on pavement; the off-road family, built to conquer mountains and dirt; the city and everyday family, making daily travel comfortable; and the special-purpose family, with distinctive aims such as hauling cargo, riding two-up or riding reclined. Of course, the boundaries aren't razor-sharp. The gravel bike sits between road and mountain bikes, and e-bikes exist in almost every genre. It's worth remembering that classification is just a map to aid understanding; real riding always crosses those boundaries.

Five ways to classify bikes

Even when bikes look alike, the key variables that define their character boil down to surprisingly few. Understand the five below and you can tell a great deal about what an unfamiliar bike is for from a single photo.

These five variables move in concert. Fitting a suspension fork, for example, lengthens the fork and raises the front end, so the head tube is shortened to compensate; wider tires require more clearance in the frame and fork and tend to lengthen the chainstays. Smaller wheels mean a longer seatpost and stem to achieve the same riding position. That's why experienced mechanics look at a bike's frame proportions before its component brands. Every silhouette in the gallery below is drawn from this kind of geometric data (wheel size, head angle, reach and stack, handlebar shape, suspension or not), so you can compare the differences in proportion between types with your own eyes.

Road family: designed for speed and efficiency

The history of the road bike is the history of bike racing. For more than 100 years, European road racing, starting with the Tour de France in 1903, has served as a laboratory testing how fast and how far a human can travel under their own power. The result is a shared grammar for road bikes: a light frame, narrow high-pressure tires and a drop bar that lets the rider crouch low. The drop bar offers several hand positions, on the tops, on the hoods above the brake levers and in the drops, so riders can shift position to spread fatigue over long distances and, when needed, fold their body to cut air resistance sharply.

On the flat, above about 25–30 km/h most of a rider's effort goes into overcoming air resistance. Because air resistance grows with the square of speed, even a small increase in speed demands a steep rise in power. On climbs, by contrast, speeds are low, so gravity, in other words weight, becomes the bigger factor. That is exactly why modern road bikes divide into 'aero' and 'lightweight' models, 'all-rounders' that balance the two, and comfort-focused 'endurance' bikes.

Aero, endurance and climbing: same road, different priorities

Aero road bikes have tube profiles shaped like wings and fully hidden cables to smooth the airflow. They're dominant in fast group rides on the flat and in sprints, but sensitive to crosswinds and fairly harsh-riding. Climbing road bikes do the opposite, focusing on shedding weight. Because the Union Cycliste Internationale (UCI) sets a minimum weight of 6.8 kg for race bikes, high-end lightweight bikes are sometimes built right to this limit. Endurance road bikes are long-distance machines with a taller head tube and longer wheelbase to ease the strain on the upper body, and their generous clearance for wide tires keeps them comfortable even on Korea's rough bike paths. For first-time road bike buyers, the safest choice is usually an endurance model.

Road bikes have seen two major changes in the past decade. One is the switch from rim brakes to disc brakes; the other is the widening of tires. Narrow 23 mm tires at high pressure were once thought to be fastest, but research and experience have shown that on real roads, because of surface vibration, 25–28 mm tires at slightly lower pressures roll with similar or even lower resistance, and 28 mm or wider has now become the de facto standard. Because disc brakes grip a rotor at the hub rather than the rim, braking stays consistent even in the rain, and designers gained freedom in rim shape and tire width.

Time trial and track: extremes shaped by the rules

Time trial (TT) bikes exist for solo races against the clock, where the rider battles the wind alone. Riders rest their elbows on long, forward-reaching aero bars, with the seat angle steepened to 76–80° so the torso lies nearly horizontal. On the final day of the 1989 Tour de France, Greg LeMond used aero bars in the time trial to overturn the overall standings by just eight seconds, an iconic moment that showed how position alone can decide a race. Triathlon bikes look almost identical to TT bikes, but because they're less constrained by cycling's race rules, they have more freedom in nutrition storage and frame shape.

Track bikes race on banked velodromes. They have a single fixed gear, with the rear wheel connected directly to the cranks, and no brakes, because in a controlled arena where everyone rides in the same direction, sudden braking is actually dangerous. The 'fixie' craze in 2000s cities brought this simple mechanical beauty to the streets, but if you ride on public roads you must fit front and rear brakes. In Korea, too, riding brakeless bikes on the road carries a very high risk of crashes and has been the target of police enforcement and public awareness campaigns.

Gravel and cyclocross: beyond the pavement

In the mid-2000s, long-distance races on the endless unpaved farm roads of the American Midwest grew popular, and the culture of riding drop-bar bikes on dirt spread rapidly, giving rise to a category of its own: Gravel bike. With a head angle 1–2° slacker than a road bike's, a long wheelbase, wide 40–50 mm tires and low gearing, these bikes stay stable on gravel, and plenty of mounts for bottles and bags make them ideal for multi-day bikepacking trips. Swap the tires and they're fast enough for the road, which has made them the go-to answer to the question 'If you could own only one bike…'.

Cyclocross bikes are far older than gravel bikes, born in the winter races of early 20th-century Europe. In races lasting about an hour, riders cross mud, sand and stairs, sometimes running with the bike on their shoulder, so wide clearances that don't clog with mud and a frame that's easy to shoulder matter. UCI race rules limit tire width to 33 mm. They look similar to gravel bikes, but their character is different: a higher bottom bracket and shorter wheelbase make them far more agile.

Touring: the goal is to go the distance

Touring bikes are the traveler's tool, carrying a tent, sleeping bag and even cooking gear in front and rear panniers over thousands of kilometers. Durability and ease of repair come before speed, so a chromoly steel frame, 36-hole wheels and a wide gear range are the traditional recipe. Chainstays of 45 cm or more keep your heels from hitting the bags as you pedal, and some riders use 'low-rider' racks that hang luggage at front-axle height to lower the center of gravity. For long trips in Korea such as the cross-country route, if you're carrying a lot of gear, a touring bike is still the most dependable choice.

Geometry and tire width: reading a bike's character in numbers

Switch between the buttons on the diagram above and you'll see that, from road to downhill, the bike stretches out front to back and the front wheel gradually 'lays back' farther forward. Four terms are all you need to understand this change.

Head angle is the angle between the ground and the head tube, which holds the front wheel. The larger (steeper) the angle, the quicker the bike changes direction with only a small turn of the bar, making it agile; the smaller (slacker) the angle, the farther the front wheel sits ahead of the rider, reducing the risk of going over the bars on steep terrain and stabilizing it at high speed in a straight line. Race road bikes are around 73° and downhill bikes about 62–63.5°; that difference of about 10° creates an entirely different ride.

Stack and reach are the vertical and horizontal distances from the center of the bottom bracket to the top of the head tube. The 'top tube length' in size charts varies with seat angle, which makes comparisons difficult, but stack and reach tell you where the handlebar is regardless of saddle position, making them the most objective way to compare different bikes. High stack and short reach put you upright; low stack and long reach stretch you out and down. Mountain bikers spend a lot of time standing, so a long reach is less of a burden; in fact, a long reach gives you room to move your body on descents.

Wheelbase is the distance between the front and rear axles. A short wheelbase makes for quick turning and instant response to acceleration; a long one improves straight-line stability and ride comfort. Even in the same size M, a race road bike is often around 1 m, while a downhill bike often exceeds 1.25 m. Add bottom bracket height (or BB drop) and you have the height of the center of gravity. A lower BB is more stable in corners but increases the risk of pedals striking the ground or rocks, which is why track bikes and BMX are actually designed with a high BB.

The tire width spectrum

Tires are the only point where the bike meets the ground. Wider tires can run lower pressures for a bigger contact patch and more shock absorption; narrower tires are lighter with less air resistance. The bars below show typical tire widths for each type as a proportion of the widest, the fat bike (about 4.8 inches, 122 mm).

Off-road family: mastering terrain

The mountain bike's origins go back to 1970s Marin County, California. Riders such as Joe Breeze, Gary Fisher and Tom Ritchey modified old cruisers and timed themselves down the fire roads of Mount Tamalpais; the race became famous as 'Repack' because the grease in the brake hubs burned off from the heat and had to be repacked every time. Their experiments led to the first mass-produced mountain bikes in the early 1980s, and the mountain bike quickly became a worldwide craze. Cross-country became an Olympic event from the 1996 Atlanta Games.

Early mountain bikes had rigid frames with no suspension, but as suspension forks spread in the 1990s and rear suspension followed, mountain bikes split into categories by terrain. Today the most important way to classify them is suspension travel, the distance the suspension can move. More travel absorbs bigger hits, but makes the bike heavier and lets pedaling energy leak away into suspension movement, reducing climbing efficiency.

From XC to downhill: balancing climbs and descents

Cross-country (XC) bikes are the lightest and most efficient mountain bikes. With 29-inch wheels and 100–120 mm of travel, they race quickly over courses of repeated climbs and descents; for beginners, a hardtail with front suspension only is still the most sensible choice. Trail bikes, with 130–150 mm of travel, are mountain all-rounders that balance the fun of climbing and descending. They focus on the joy of weekend rides rather than racing, and a dropper seatpost, which changes saddle height on the move, is standard. Recently a halfway genre called 'downcountry' has also emerged, trimming travel slightly and adding XC-level efficiency.

Enduro takes its name from races in which only the descents are timed. Riders must pedal up the climbs themselves, but the descents demand near-downhill aggression, so these bikes combine 150–180 mm of travel with a slack head angle of around 64° and a steep seat angle. Downhill (DH) bikes give up on pedaling uphill in exchange for descending the roughest terrain as fast as possible. They feature around 200 mm of travel, a dual-crown fork supported by two crowns, upper and lower, and a head angle of around 63°, and they're mostly ridden at bike parks with lifts or shuttle vehicles. A full-face helmet and body armor are essential, not optional.

Over the past decade or so, mountain bike geometry has followed a clear trend: 'longer, lower, slacker', meaning longer reach, lower bottom brackets and slacker head angles. As a result, today's trail bikes have numbers similar to the enduro bikes of 10 years ago, with steeper seat angles to keep the front wheel down on climbs. Wheels have also grown from 26 to 27.5 and 29 inches, and the 'mullet' setup, a 29-inch front with a 27.5-inch rear, has become common in enduro and downhill.

BMX and dirt jump: small wheels, big skills

BMX began in the early 1970s when kids in California raced bikes on dirt tracks in imitation of motocross riders. Twenty-inch wheels, a small, tough frame and a tall handlebar are common to all BMX bikes. BMX racing is a short, intense race in which several riders start together from a sloped starting gate and tackle jumps and banked corners; it has been an Olympic event since the 2008 Beijing Games. BMX freestyle pits riders against each other with aerial and balance tricks in skateparks and on the street; the park event became an Olympic discipline for the first time at Tokyo 2020 (held in 2021). The bikes carry trick-specific equipment such as pegs on the axles and rotors that let the bar spin endlessly.

Dirt jump bikes combine BMX trick culture with mountain bike components. With 26- or 24-inch wheels, short chainstays, a very low saddle and a stiff 80–100 mm suspension fork, they're optimized for launching and twisting the bike in the air on dirt jumps and pump tracks. As more local governments in Korea build pump tracks, riders who want to practice bike-handling skills without heading to the mountains are turning to this genre.

Fat bikes: floating on snow and sand

Fat bike tires, an ultra-wide 3.8–5 inches, let these bikes 'float' over snow and sand. They grew out of experiments by riders in Alaska's winter snow races and places such as Patagonia in South America, who widened rims by joining two together, and went mainstream when production models appeared in the mid-2000s. Dropping the pressure to around 0.5 bar lets the tire squash and wrap around the terrain for remarkable grip and cushioning, but fat bikes are heavy with high rolling resistance, so they're slow on pavement. It's a genre that offers special enjoyment to riders in beach-rich areas or those who want to keep riding through winter.

City and everyday bikes: designed for daily life

If sports bikes push the limits of performance, everyday bikes aim for frictionless daily life. Questions at the heart of the design include: Can you ride it in ordinary clothes? Will it keep muddy spray off your clothes in the rain? Is it easy to get going after waiting at a light? Can you carry it into your home or onto the subway? That's why everyday bikes come standard with fenders, a chain guard, a rack, a kickstand and lights, all things sports bikes leave off to save weight.

Hybrids: the widest door into cycling

Hybrid bikes were born after the mountain bike boom of the 1980s and '90s, from attempts to blend the comfortable position of a mountain bike with the light feel of a road bike. 700C wheels, 35–45 mm tires and a straight flat bar are the basic recipe. In Korea, with well-developed riverside bike paths along the Han River and elsewhere, hybrids remain consistently popular for combining commuting and exercise. The range is wide, from comfort models with suspension forks to fitness models that are essentially road bikes with a flat bar in place of the drop bar, so if you ride long distances choose a lighter model with narrower tires, and for rough surfaces and short distances, one with wider tires.

City and Dutch bikes: the answer from the kingdom of cycling

In the Netherlands, where cycling accounts for a large share of all trips, decades of refinement have produced the everyday-optimized city bike. Often called the 'Dutch bike', it has a step-through frame you can mount without lifting your leg high, swept-back handlebars that keep your back upright, a case that fully encloses the chain, and internal hub gears that are less prone to rust or dropped chains. At around 20 kg it's heavy, but because you can ride it in a suit or in the rain without any special preparation, it's arguably the perfected form of the everyday bike. In Korea, however, with its walk-up apartments and hilly terrain, the weight can be a drawback, so check how and where you'll store it first.

Mini velos and folding bikes: small wheels rediscovered

Small-wheeled bikes were long seen as 'for kids' or 'slow', but in 1962 Britain's Alex Moulton shattered that prejudice with a small-wheeled bike featuring suspension, opening up a new genre. Mini velo is the name commonly used in Korea and Japan for any adult-frame bike with small wheels of around 20 inches. Small wheels have little rotational inertia, so they get away briskly, and the short bike fits easily into elevators and entryways. But because the wheels must turn more times to reach the same speed, mini velos use large chainrings, and since you feel small surface bumps more directly, tire width and pressure have a big effect on ride comfort.

Folding bikes go one step further, folding the frame to reduce its bulk. The Brompton, designed by Andrew Ritchie in Britain in the mid-1970s, folds to the size of a suitcase with its 16-inch wheels and has become synonymous with folding bikes. For commutes combined with the subway or bus, storage at the office, or trips with the bike in the car trunk, nothing beats a folding bike. The folding hinges are safety-critical, so make a habit of checking that they're locked before you ride and having them inspected immediately if any play develops.

Cruisers: the art of slowness

Cruiser bikes are descendants of the balloon-tire bikes popular in 1930s America. The position created by fat tires, a curved steel frame, a wide sprung saddle and a tall, swept-back handlebar is far from fast, but the relaxed feel of rolling slowly along a beach promenade or through a park is hard for other bikes to match. Some models use a coaster brake, which you operate by pedaling backward, so it takes some getting used to at first. Interestingly, these cruisers were exactly what the early mountain bike pioneers mentioned earlier modified. The most laid-back bike is the ancestor of the toughest.

E-bikes: a motor added to every genre

E-bike are less a specific form than an attribute, power assistance, that can be added to almost any genre. They range from city and hybrid models to e-MTBs, e-cargo bikes and e-folding bikes, and they lower the biggest barriers to commuting by bike: hills and headwinds. In Korea, e-bikes allowed on bike paths must meet legal standards: they must be pedal-assist, with the motor helping only while you pedal; the motor must cut out above 25 km/h; and the total weight must be under 30 kg. Motor types, batteries, regulations and care tips are covered in detail in the E-bikes chapter.

Special-purpose bikes: form that solves problems

The final family consists of bikes that boldly reshape the usual bicycle form to solve a particular problem. They're few in number, but they best demonstrate just how adaptable the bicycle is.

Cargo bikes: the bicycle that replaces the car

Cargo bike designs carry both people and goods. The main types are the long john (also called a 'bakfiets' in Dutch-speaking countries), with a large cargo box between the front wheel and handlebar; the longtail, with an extended rear end carrying a rack and seats; and the three-wheeled trike. On a long john the front wheel sits far ahead of the cargo box, so the handlebar and fork are linked by a rod for steering, and a small 20-inch front wheel keeps the box low for a stable center of gravity. In Copenhagen and Amsterdam, parents taking two children to daycare by cargo bike are a common sight, and e-cargo bikes with electric assist are also used for urban parcel delivery and by small businesses. Many are well over 2 m long, so be sure to check your storage space and turning circle.

Recumbents: forbidden speed

Recumbent bikes are ridden leaning back against a backrest like a chair, with the legs stretched forward. When France's Francis Faure beat the Hour Record of the day (the distance ridden in one hour) on a recumbent in 1933, the UCI decided the following year to separate such machines from conventional bicycle records. Recumbents then disappeared from mainstream racing, but recumbents with aerodynamic fairings still hold the human-powered vehicle speed records. Because body weight is spread across the whole back and buttocks, there's almost no wrist, neck or perineal pain, making them a good alternative for people whose back or joint problems make regular bikes difficult. They sit low, though, so it's wise to fit a flag and lights to stay visible on the road.

Tandems: two riders as one

Tandem bicycles seat two riders, one behind the other, pedaling together. The front rider (the captain) handles steering, shifting and braking, while the rear rider (the stoker) concentrates on pedaling and balance. Two riders' power is combined but the air resistance is close to that of a single bike, so tandems are very fast on the flat and downhill, and their greatest appeal is that two people of very different fitness can ride together at the same speed. Tandems are also used in Paralympic cycling, where visually impaired athletes ride with sighted pilots. Given the greater weight and loads, brakes and wheels must be much stronger than on a regular bike.

Kids' and balance bikes: the new standard for a first bike

For a long time children learned to ride on bikes with training wheels, but these days it's become common to learn balance first on a pedal-less balance bike. Children push off the ground with both feet and naturally learn to lift their feet and balance, so when they move on to a pedal bike, many can ride straight away without training wheels. When choosing a kids' bike, look first not at wheel size but at whether the child can sit on the saddle with both feet on the ground, and whether the bike is too heavy relative to the child's weight. As they grow they'll move through 12, 14, 16, 20 and 24-inch sizes, and it's best to make wearing a helmet a habit from the very start.

Pre-purchase checklist: what to do after choosing a type

Once you've chosen a type, you're halfway there. The other half is choosing, within that type, the one bike that suits your body and your life. Many people start by comparing component tiers and weight, but what actually determines satisfaction is, surprisingly, the basics: size, tires and storage. No matter how good the components, a frame that doesn't fit will hurt your knees and back, tires that don't suit the surface will ride badly, and if storage is a hassle you'll end up not riding at all.

When setting a budget, factor in essential gear beyond the bike itself, such as a helmet, lights, a lock, a pump, basic tools and bottle cages. Setting aside roughly 10–20% of the bike's price gives you some leeway. Also remember that the more disc brakes, suspension and electronics a bike has, the higher its regular maintenance costs. The table below gives rough ranges based on Korean retail prices in the mid-2020s; they can vary greatly with exchange rates, brand policies and sale seasons.

Five things to check before visiting a shop

1. Sum up where and how far you'll mostly ride in one sentence. The more specific, such as “8 km each way commuting on weekdays, 50 km along the Han River on weekends”, the more accurate the recommendations.
2. Measure your height and inseam (inside leg length). This lets you do a first pass using the recommended ranges in brands' size charts.
3. Check where you'll store the bike and how you'll get it there. Stairs, elevator size and whether you'll combine it with public transport determine how much weight matters and whether you need a folding bike.
4. Check tire clearance. Room to fit wider tires later greatly expands what the bike can do.
5. Always test-ride. Even for the same type and size, geometry differs between brands, and the difference you feel is bigger than you'd expect.

FAQ

Now that you understand the types of bicycle, it's time to find out what parts a bike is made of and what each one does. In the next chapter, we take the bicycle apart and examine it piece by piece, from the frame to the drivetrain, brakes and wheels.