Bicycle helmets can reduce injury in the event of a collision or accident, and a suitable helmet is legally required of riders in many jurisdictions. A pair of wheels may be called a wheelset, especially in the context of ready-built "off the shelf", performance-oriented wheels. Without a freewheel, coasting is impossible, so when the rear wheel is moving, the cranks are moving. A rear hub brake may be either hand-operated or pedal-actuated, as in the back pedal coaster brakes which were popular in North America until the 1960s. Upright handlebars, the norm in Europe and elsewhere until the 1970s, curve gently back toward the rider, offering a natural grip and comfortable upright position.
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In a lower gear, every turn of the pedals leads to fewer rotations of the rear wheel. A very small number of bicycles use a shaft drive to transmit power, or special belts. ] More expensive bikes use carbon fibre due to its significantly lighter weight and profiling ability, allowing designers to make a bike both stiff and compliant by manipulating the lay-up. These are inherently more aerodynamic than upright versions, as the rider may lean back onto a support and operate pedals that are on about the same level as the seat. The seat stays connect the top of the seat tube (at or near the same point as the top tube) to the rear fork ends.
Bicycles are popular targets for theft, due to their value and ease of resale. Countries which require adult cyclists to wear helmets include Spain, New Zealand and Australia. Along with advertising, and to gain free publicity, Albert A. Pope litigated on behalf of cyclists.
Early in its development, as with automobiles, there were restrictions on the operation of bicycles. As of 2009update, 130 million bicycles were sold every year globally and 66% of them were made in China. One of the major reasons for the proliferation of Chinese-made bicycles in foreign markets is the lower cost of labor in China. Despite this shift in production, as nations such as China and India become more wealthy, their own use of bicycles has declined due to the increasing affordability of cars and motorcycles. Early bicycles were an example of conspicuous consumption, being adopted by the fashionable elites.
Seating
The European Committee for Standardization (CEN) also has a specific Technical Committee, TC333, that defines European standards for cycles. Bicycle lights, reflectors, and helmets are required by law in some geographic regions depending on the legal code. Toe-clips and toestraps and clipless pedals help keep the foot locked in the proper pedal position and enable cyclists to pull and push the pedals. Bicycles can also be fitted with a hitch to tow a trailer for carrying cargo, a child, or both.
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Morris Motors Limited (in Oxford) and Škoda also began in the bicycle business, as did the Wright brothers. Bicycles helped create, or enhance, new kinds of businesses, such as bicycle messengers, traveling seamstresses, riding academies, and racing rinks. In addition, by serving as a platform for accessories, which could ultimately cost more than the bicycle itself, it paved the way for the likes of the Barbie doll.
Los Angeles removed a small amount of seating on some trains to make more room for bicycles and wheel chairs. Suspension is especially important on recumbent bicycles, since while an upright bicycle rider can stand on the pedals to achieve some of the benefits of suspension, a recumbent rider cannot. Track bicycles do not have brakes, because all riders ride in the same direction around a track which does not necessitate sharp deceleration. With comfort bikes and hybrids, cyclists sit high over the seat, their weight directed down onto the saddle, such that a wider and more cushioned saddle is preferable. Some, mainly utility, bicycles use hub gears with between 3 and 14 ratios, but most use the generally more efficient dérailleur system, by which the chain is moved between different cogs called chainrings and sprockets to select a ratio. Virtually all professional racing bicycles now use carbon fibre frames, as they have the best strength to weight ratio.
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For racing bikes where the rider is bent over, weight is more evenly distributed between the handlebars and saddle, the hips are flexed, and a narrower and harder saddle is more efficient. Most bikes have two or three chainrings, and from 5 to 12 sprockets on the back, with the number of theoretical gears calculated by multiplying front by back. Bamboo, a natural composite material with high strength-to-weight ratio and stiffness has been used for bicycles since 1894. Historically, materials used in bicycles have followed a similar pattern as in aircraft, the goal being high strength and low weight. Furthermore, it was considered "unladylike" for women to open their legs to mount and dismount—in more conservative times women who rode bicycles at all were vilified as immoral or immodest. The rear triangle consists of the seat tube and paired chain stays and seat stays.
The chain stays run parallel to the chain, connecting the bottom bracket to the rear dropout, where the axle for the rear wheel is held. In terms of the ratio of cargo weight a bicycle can carry to total weight, it is also an efficient means of cargo transportation. This lean is induced by a method known as countersteering, which can be performed by the rider turning the handlebars directly with the hands or indirectly by leaning the bicycle. The combined center of mass of a bicycle and its rider must lean into a turn to successfully navigate it. This steering is usually provided by the rider, but under certain conditions, may be provided by the bicycle itself. Military uses of bicycles include communications, reconnaissance, troop movement, supply of provisions, and patrol, such as in bicycle infantries.
- One of the profound economic implications of bicycle use is that it liberates the user from motor fuel consumption.
- Bicycle tires usually have a marking on the sidewall indicating the pressure appropriate for that tire.
- A bicycle stays upright while moving forward by being steered so as to keep its center of mass over the wheels.
- Around the turn of the 20th century, bicycles reduced crowding in inner-city tenements by allowing workers to commute from more spacious dwellings in the suburbs.
Groupset generally refers to all of the components that make up a bicycle excluding the bicycle frame, fork, stem, wheels, tires, and rider contact points, such as the saddle and handlebars. Disc brakes are more common for mountain bikes, tandems and recumbent bicycles than on other types of bicycles, due to their increased power, coupled with an increased weight and complexity. While some women's bicycles continue to use this frame style, there is also a variation, the mixte, which splits the top tube laterally into two thinner top tubes that bypass the seat tube on each side and connect to the rear fork ends.
Since then aluminum alloy frames and other components have become popular due to their light weight, and most mid-range bikes are now principally aluminum alloy of some kind.
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