Hybrid bicycles blend characteristics from more specialized road bikes, touring bikes and mountain bikes to create a general-purpose, user-friendly bicycle. Their stability, comfort and ease of use makes them popular with beginning bicyclists, casual riders and urban commuters.
Hybrids may integrate the flat handlebars, upright posture and brake system of a mountain bike. They may also have numerous accommodations for accessories (front and rear racks, water bottles, and fenders) typically found on a touring bike. Many also have the larger wheel diameter (e.g. 700c) and lighter componentry of a road bike — and a rim/tire configuration that falls between the road/touring bikes and mountain bikes.
Hybrid bikes have spawned numerous sub-categories satisfying diverse ridership. They are classified by their design priorities, such as those optimized for comfort or fitness — and those offered as city, cross or commuter bikes.
Trekking bike 
Cross bike 
So-called cross bikes utilize a road bicycle frame similar to a racing or sport/touring bicycle, and are normally equipped with nearly flat handlebars to provide a more upright riding position than a racing or sport/touring bike. As a hybrid bike intended for general recreational and utility use, the cross bike differs from the cyclo-cross bicycle, which is a racing bicycle purposely designed to compete in the sport of cyclo-cross competition. Cross bikes are fitted with 700c wheels using somewhat wider semi-treaded tires (1.125–1.25 inches, or 28–32 mm) than those fitted to most racing or sport/touring models. The additional tire width and tread is intended to give the cross bike hybrid some ability to deal with rough or littered surfaces that might be encountered on paved or unpaved bike trails, such as gravel, leaves, hard-packed sand, and shallow mud. Most cross bikes are biased towards moderate off-pavement use and light weight, and as such are not normally fitted with fenders, lights, or carrier racks. The larger 700c wheels are a little faster on paved surfaces and can give an advantage for longer trips or for touring purposes.
Commuter bike 
The commuter bike is a hybrid designed specifically for commuting over short or long distances. It typically features derailleur gearing, 700c wheels with fairly light 1.125 inch (28 mm) tires, a carrier rack, full fenders, and a frame with suitable mounting points for attachment of various load-carrying baskets or panniers. It sometimes, though not always, has an enclosed chainguard to allow a rider to pedal the bike in long pants without entangling them in the chain. A well-equipped commuter bike typically features front and rear lights for use in the early morning or late evening hours encountered at the start or end of a business day.
City bike 
Similar to the commuter bike, the city bike is more optimized for urban commuting. The city bike differs from the familiar European city bike in its mountain bike heritage, gearing, and strong yet lightweight frame construction. It usually features mountain bike-sized (26-inch) wheels, a more upright seating position, and fairly wide 1.5–1.95 inch (38–50 mm) heavy belted tires designed to withstand road hazards commonly found in the city, such as broken glass. Using a sturdy welded chromoly or aluminum frame derived from the mountain bike, the city bike is more capable at handling urban hazards such as deep potholes, drainage grates, and jumps off city curbs. City bikes are designed to have reasonably quick, yet solid and predictable handling, and are normally fitted with full fenders for use in all weather conditions. A few city bikes may have enclosed chainguards, while others may be equipped with suspension forks, similar to mountain bikes. City bikes may also come with front and rear lighting systems for use at night or in bad weather.
Comfort bike 
Another subclass of the hybrid category is the comfort bike. Comfort bikes are essentially modern versions of the old roadster and sports roadster bicycle, though modern comfort bikes are often equipped with derailleur gears rather than hub gears. They typically have a modified mountain bike frame with a tall head tube to provide an upright riding position, 26-inch wheels, and 1.75 or 1.95 inch (45 or 50 mm) smooth or semi-slick tires. Comfort bikes typically incorporate such features as front suspension forks, seat post suspension with wide plush saddles, and drop-center, angled North Road-style handlebars designed for easy reach while riding in an upright position.
- Ballantine, Richard (2001). Richard's 21st Century Bicycle Book. New York: Overlook Press. pp. 32–39. ISBN 1-58567-112-6.
- "Trekking bike". Cyclists' Touring Club.
- Sheldon Brown. "Sheldon Brown's Bicycle Glossary – Trekking Bicycle".
- "Sheldon Brown's Bicycle Glossary – Hybrid Bicycle". Retrieved 2008-11-07.
- Howells, Bob, and Lehrer, John, A City Bike Sampler, Outside Magazine (March 1992), Vol. 17, pp. 88-91
- Mellion, Morris B., Sports Medicine Secrets, Elsevier Health Sciences, 3rd ed. (2003), ISBN 1-56053-548-2, ISBN 978-1-56053-548-5, p. 552
- Museum of Mountain Bike Art & Technology Article
- Howells, pp. 88–91
Media related to Hybrid bikes at Wikimedia Commons