Bicycle wheel

The first wheel to use the tension in metal spokes was invented by Sir George Cayley to achieve lightness in his 1853 glider. ==Construction==

The first bicycle wheels followed the traditions of carriage building: a wooden hub, a fixed steel axle (the bearings were located in the fork ends), wooden spokes and a shrink fitted iron tire. A typical modern wheel has a metal hub, wire tension spokes and a metal or carbon fiber rim which holds a pneumatic rubber tire. Hub A hub is the center part of a bicycle wheel. It consists of an axle, bearings and a hub shell. The hub shell typically has two machined metal flanges to which spokes can be attached. Hub shells can be one-piece with press-in cartridge or free bearings or, in the case of older designs, the flanges may be affixed to a separate hub shell. Axle The axle is attached to dropouts on the fork or the frame. The axle can attach using a: • Quick release skewer - a lever and skewer that pass through a hollow axle designed to allow for installation and removal of the wheel without any tools (found on most modern road bikes and some mountain bikes). • Nut - the axle is threaded and protrudes past the sides of the fork/frame. (often found on track, fixed gear, single speed, BMX and inexpensive bikes) • Bolt - the axle has a hole with threads cut into it and a bolt can be screwed into those threads. (found on some single speed hubs, Cannondale Lefty hubs) • Thru-axle - a removable axle with a threaded end that is inserted through a hole in one fork leg, through the hub, and then screwed into the other fork leg. Some axles have integrated cam levers that compress axle elements against the fork leg to lock it in place, while others rely on pinch bolts on the fork leg to secure it. Diameters for front thru axles include 20 mm, 15 mm, 12 mm, and 9 mm. Rear axles typically have diameters of 10 or 12 mm. Most thru axles are found on mountain bikes, although increasingly disc-braked cyclocross and road bikes are using them. Thru axles repeatably locate the wheel in the fork or frame, which is important to prevent misalignment of brake rotors when using disc brakes. Unlike other axle systems (except Lefty), the thru axle is specific to the fork or frame, not the hub. Hubs/wheels do not include axles, and the axle is generally supplied with the fork or frame. Adapters are usually available to convert wheels suitable for a larger thru axle to a smaller diameter, and to standard 9mm quick releases. This allows a degree of re-use of wheels between frames with different axle specifications. • Female axle - hollow center axle, typically 14, 15, 17, or 20 mm in diameter made of chromoly and aluminum, with two bolts thread into on either side. This design can be much stronger than traditional axles, which are commonly only 8 mm, 9 mm, 9.5 mm, or 10 mm in diameter. (found on higher end BMX hubs and some mountain bike hubs) Since the 1980s, bicycles have adopted standard axle spacing: the hubs of front wheels are generally 100 mm wide fork spacing, road wheels with freehubs generally have a 130 mm wide rear wheel hub. Mountain bikes have adopted a 135 mm rear hub width, which allows clearance to mount a brake disc on the hub or to decrease the wheel dish for a more durable wheel. File:Through-axle and derailleur hanger 1.jpg|Three M12 through-axles. Top: 1 mm pitch axle for bicycle trailer shown with a universal derailleur hanger (UDH). Bottom: 1.5 mm pitch axle shown with a pre-UDH derailleur hanger Bearings The bearings allow the hub shell (and the rest of the wheel parts) to rotate freely about the axle. Most bicycle hubs use steel or ceramic ball bearings. Some hubs use serviceable "cup and cone" bearings, whereas some use pre-assembled replaceable "cartridge" bearings. A "cup and cone" hub contains loose balls that contact an adjustable 'cone' that is screwed onto the axle and a 'race' that is pressed permanently into the hub shell. Both surfaces are smooth to allow the bearings to roll with little friction. This type of hub can be easily disassembled for lubrication, but it must be adjusted correctly; incorrect adjustment can lead to premature wear or failure. In a "cartridge bearing" hub, the bearings are contained in a cartridge that is shaped like a hollow cylinder where the inner surface rotates with respect to the outer surface by the use of ball bearings. The manufacturing tolerances, as well as seal quality, can be significantly superior to loose ball bearings. The cartridge is pressed into the hub shell and the axle rests against the inner race of the cartridge. The cartridge bearing itself is generally not serviceable or adjustable; instead the entire cartridge bearing is replaced in case of wear or failure. Hub shell and flanges The hub shell is the part of the hub to which the spokes (or disc structure) attach. The hub shell of a spoked wheel generally has two flanges extending radially outward from the axle. Each flange has holes or slots to which spokes are affixed. Some wheels (like the Full Speed Ahead RD-800) have an additional flange in the center of the hub. Others (like some from Bontrager and Zipp) do not have a noticeable flange. The spokes still attach to the edge of the hub but not through visible holes. Other wheels (like those from Velomax/Easton) have a threaded hub shell that the spokes thread into. On traditionally spoked wheels, flange spacing affects the lateral stiffness of the wheel, with wider being stiffer, and flange diameter affects the torsional stiffness of the wheel and the number of spoke holes that the hub can accept, with larger diameter being stiffer and accepting more holes. allowing high (6–10 bar, 80–150 psi) air pressure. Tubular or sew-up rims Some rims are designed for tubular tires which are torus shaped and attached to the rim with adhesive. The rim provides a shallow circular outer cross section in which the tire lies instead of flanges on which tire beads seat. Tubeless A tubeless tire system requires an airtight rim — capable of being sealed at the valve stem, spoke holes (if they go all the way through the rim) and the tire bead seat — and a compatible tire. Universal System Tubeless (UST), originally developed by Mavic, Michelin and Hutchinson for mountain bikes is the most common system of tubeless tires/rims for bicycles. One end of each spoke is threaded for a specialized nut, called a nipple, which is used to connect the spoke to the rim and adjust the tension in the spoke. This is normally at the rim end. The hub end normally has a 90-degree bend to pass through the spoke hole in the hub, and a head so it does not slip through the hole. This is the J-bend type. Another type is straight pull spokes, which have no bend at the hub end, just a head. The major materials for spoke nipples are aluminum and brass. Double-butted spokes have reduced thickness over the center section and are lighter, more elastic, and more aerodynamic than spokes of uniform thickness. Single-butted spokes are thicker at the hub and then taper to a thinner section all the way to the threads at the rim. Cross section Spokes are usually circular in cross-section, but high-performance wheels may use spokes of flat or oval cross-section, also known as bladed, to reduce aerodynamic drag. Some spokes are hollow tubes. Wheels with fewer spokes have an aerodynamic advantage, as the drag is reduced. The reduced number of spokes also results in a larger section of the rim being unsupported, necessitating stronger and often heavier rims. Some wheel designs also locate the spokes unequally into the rim, which requires a stiff rim hoop and correct tension of the spokes. Conventional wheels with spokes distributed evenly across the circumference of the rim are considered more durable and forgiving to poor maintenance. The more general trend in wheel design suggests technological advancement in rim materials may result in further reduction in the number of spokes per wheel. Lacing Lacing is the process of threading spokes through holes in the hub and rim Alternatives A wheel can be formed in one piece from a material such as thermoplastic (glass-filled nylon in this case), carbon fiber or aluminium alloy. Thermoplastic is commonly used for inexpensive BMX wheels. They have a low maximum tire pressure of 45 psi (3bars or atmospheres). Carbon fiber is typically used for high-end aerodynamic racing wheels. Disc wheels Disc wheels are designed to minimize aerodynamic drag. A full disc is usually heavier than traditional spoke wheels, and can be difficult to handle when ridden with a cross wind. For this reason, international cycling organizations often ban disc wheels or limit their use to the rear wheel of a bicycle. However, international triathlon federations were (and are still) less restrictive and this is what led to the wheels' initial usage growth in popularity in the 1980s. A disc wheel may simply be a fairing that clips onto a traditional, spoke wheel, addressing the drag that the spokes generate by covering them; or the disc can be integral to the wheel with no spokes inside. In the latter case, carbon fiber is the material of choice. A spoke wheel with a disc cover may not be legal under UCI (Union Cycliste Internationale) rules because it is a non-structural fairing while it may be legal under ITU (International Triathlon Union) rules. A compromise that reduces weight and improves cross wind performance has a small number (three or four) tension-compression spokes molded integral to the rim – also typically carbon fiber. ==Types==

Bicycle wheels can be categorized by their primary use. Road/racing bicycle wheels rear wheel with "G3" triplet spoke lacing. There are 18 tangential spokes on the right side, but only 9 radial on the left. Picture also shows a 10-speed cassette For road bicycle racing performance there are several factors which are generally considered the most important: • aerodynamics • weight • rotational inertia • hub/bearing smoothness • stiffness Semi-aerodynamic and aerodynamic wheelsets are now commonplace for road bicycles. Aluminum rims are still the most common, but carbon fiber is also becoming popular. Carbon fiber is also finding use in hub shells to reduce weight; however, because of the hub's proximity to the center of rotation reducing the hub's weight has less effect to the rotational inertia than reducing the rim's weight. Semi-aerodynamic and aerodynamic wheelsets are characterized by greater rim depth, which is the radial distance between the outermost and the innermost surfaces of the rim; a triangular or pyramidal cross-section; and by fewer numbers of spokes, or no spokes at all—with blades molded of composite material supporting the rim. The spokes are also often flattened in the rotational direction to reduce wind drag. These are called bladed spokes. However, semi-aerodynamic and aerodynamic wheelsets tend to be heavier than more traditional spoked wheelsets due to the extra shapings of the rims and spokes. More importantly, the rims must be heavier when there are fewer spokes, as the unsupported span between spokes is greater. A number of wheel manufacturers are now producing wheels with roughly half the spokes of the highest performance traditional wheel from the 1980s, with approximately the same rotational inertia and less total weight. These improvements have been made possible primarily through improved aluminum alloys for the rims. Most clincher carbon fiber wheelsets, such as those made by Zipp and Mavic, still use aluminum parts at the clinching part of the rim. An increased number of all-carbon rims, such as Campagnolo Hyperon Ultra Clincher, Viva v8 wheels, Bontrager's Carbon Clincher wheels, DT Swiss RRC1250, Corima Winium and Aero (also tubeless, see below) and Lightweight Standard C wheelsets are now available. 700C road bicycle wheels / ISO 622 mm Touring, race, and cyclo-cross bicycles may have vastly different design goals for their wheels. Aerodynamic performance and low weight are beneficial for road bicycles, while for cyclo-cross strength gains importance, and for touring bicycles, strength becomes more important again. However, this diameter of rim, identical in diameter to the "29er" rim, is by far the most common on these styles of bicycles. Road wheels may be designed for tubular or clincher tires, commonly referred to as "700C" tires. 650C triathlon bicycle wheels / ISO 571 mm These wheels experienced a brief popularity in the 1990s on triathlon bikes. This tradition was started initially because the early mountain bike pioneers procured the wheels for their early bikes from American-made bicycles rather than the larger European standards in use. The typical 26-inch rim has a diameter of and an outside tire diameter of about . 27.5 inch / ISO 584 mm 27.5-inch mountain bike wheels 36 inch / ISO 787 36-inch wheels have been developed to create bikes more proportional for taller riders. BMX wheels There are two distinct wheel sizes that get described as 20 in., and both get used in the BMX sport. 20 inch / ISO 406 mm Usually 20 inches in diameter (rim diameter of 406 mm), BMX wheels are small for several reasons: they are suitable for young and small riders; their lower cost is compatible with inexpensive bicycles; the size makes them stronger to withstand the additional loads generated by BMX jumps and stunts; and to reduce rotational inertia for easier wheel acceleration. 20 inch / ISO 451 mm Nominally 20 x 1-1/8″ or 20 x 1-3/8″, with rim diameter 451 mm. These are intended for racing by lightweight BMX riders, and sometimes referred to as "skinnies". The size is also used on classic British folding or shopping bikes. ==Technical aspects==

Sizes Bicycle rims and tires came in many different types and sizes before efforts were made to standardize and improve wheel/tire compatibility. The International Organization for Standardization (ISO) and the European Tyre and Rim Technical Organisation (ETRTO) define a modern, unambiguous system of sizing designations and measurement procedures for different types of tires and rims in international standard ISO 5775. For example: • For wired-edge tires the ISO designation lists the width of the inflated tire and the "bead-seat diameter", both in millimeters and separated by a hyphen: 37-622. The bead seat diameter (BSD) is the diameter of the surface of the rim upon which the tire bead sits. • For rims the ISO designation lists the rim's bead seat diameter and the rim's inner width, both in millimeters and separated by a cross, along with a letter code for the rim type (e.g., "C" = Crochet-type): 622x19C In practice, most tires (and inner tubes) sold today carry, in addition to the modern ISO 5775-1 designation, some historic size markings, which are still widely used: • an old French tire designation that was based on the approximate outer diameter of the inflated tire in millimeters. The Japanese Industrial Standard JIS D 9112 continues to provide an official definition for the French tire designations. For example: 700×35 C. • an old British inch-based designation: 597 mm (26 × ), 590 mm (26 × ), 630 mm (27 × ), and 635 mm (28 × ) Which designation is most popular varies with region and type of bicycle. For a comprehensive equivalence table between old and new markings, see the ISO 5775 article, the table in Annex A of the ISO 5772 standard, as well as Tire Sizing by Sheldon Brown. Most road and racing bicycles today use 622 mm diameter (700C) rims, though 650C rims are popular with smaller riders and triathletes. The 650C size has the ISO diameter size of 571 mm. Size 650B is 584 mm and 650A is 590 mm. 650B is being promoted as a 'best of both worlds' size for mountain biking. Most adult mountain bikes use 26 inch wheels. Smaller youth mountain bikes use 24 inch wheels. The larger 700C (29 inch) wheels have enjoyed some recent popularity among off-road bicycle manufacturers. These rims are the same bead seat diameter as 700C wheels and are generally compatible with bicycle frames and tires designed for the 700C standard, however, rims designated as 29 inch are designed for wider tires than rims designated 700C, so frame clearance may be an issue. The formerly popular 27 inch (630 mm) wheel size is now rare. Children's bicycles are commonly sized primarily based on wheel diameter rather than seat tube length (along the rider's inseam) dimension. Thus, a wide range of small bike wheels are still found, ranging from diameter to . Smaller wheel sizes are also found on folding bicycles to minimise the folded size. These range from 16-inch diameter (e.g. Brompton) through 20 inches (e.g. Bike Friday) up to even 26 inches. Wheel rims also come in a variety of widths to provide optimum performance for different uses. High performance road racing rims are narrow, 18 mm or so. Wider touring or durable off-road tires require rims of 24 mm wide or more. • 650 - ISO 32-597 (26 ⋅ ) - Older British sport bikes. Schwinns with narrow tires. • 650A - ISO 37-590 (26 ⋅ ) - Common on many vintage frames ranging from American-made Murray and Huffy as well as English and French manufactures like Raleigh and Peugeot. • 650B - ISO 40-584 (26 ⋅ ) - Also 650B demi-ballon. French tandems, Porteurs, touring bicycles; enjoying a revival. Widths of tires and corresponding ISO width designations may vary, though the wheel outside diameter remains approximately the same. 28 inch Traditionally, there were four different sizes of 28-inch diameter wheels, from the narrow tires to the widest, they all measured the same outside diameter, which coincide with four different families of 700 tire sizes, these are 700, 700A, 700B and 700C. The largest of these rims (ISO 647mm/642mm) with the narrower tires are no longer available. Rolling resistance There are a number of variables that determine rolling resistance: tire tread, width, diameter, tire construction, tube type (if applicable), and pressure are all important. Smaller diameter wheels, all else being equal, have higher rolling resistance than larger wheels. "Rolling resistance increases in near proportion as wheel diameter is decreased for a given constant inflation pressure.". Rotating mass Due to the fact that wheels rotate as well as translate (move in a straight line) when a bicycle moves, more force is required to accelerate a unit of mass on the wheel than on the frame. In wheel design, reducing the rotational inertia has the benefit of more responsive, faster-accelerating wheels. To accomplish this, wheel designs are employing lighter rim materials, moving the spoke nipples to the hub or using lighter nipples such as aluminum. Note however that rotational inertia is a factor only during acceleration (and deceleration/braking). At constant speed, aerodynamics are a significant factor. For climbing, total mass remains important. See Bicycle performance for more detail. Dish The hub flanges of modern tension-spoked bicycle wheels are always spaced wider than where the spokes attach to the rim. When viewed in cross section, the spokes and hub form a triangle, a structure that is stiff both vertically and laterally. In three dimensions, if the spokes were covered (visualize paper covering the spokes on each side), they would form two cones or "dishes." The greater the separation between the hub flanges, the deeper the dishes, and the stiffer and stronger the wheel can be laterally. The more vertical the spokes, the shallower the dish, and the less stiff the wheel will be laterally. The dishes on each side of a wheel are not always equal. The cogset (freewheel or cassette) of a rear wheel and disc brake rotors, if installed, takes up width on the hub, and so the flanges may not be located symmetrically about the center plane of the hub or the bike. Since the rim must be centered, but the hub flanges are not, there is a difference in dish between the two sides. Such an asymmetrical wheel is called a "dished" wheel. The side of the wheel with less dish has slightly shorter but significantly higher-tensioned spokes than the side with more dish. Several different techniques have been tried to minimize this spoke asymmetry. In addition to modified hub geometry, some rims have off-center spoke holes, and the mounting of common J-bend spokes at the hub flange can be altered "inboard" or "outboard".{{cite web A truing stand or a dishing gauge, can be used to measure the position of the rim relative to the hub. Thus "dishing" is also used to describe the process of centering the rim on the hub, even in the case of symmetrical wheels.{{cite web Stiffness The stiffness of a bicycle wheel can be measured in three primary directions: radial, lateral, and torsional. The radial stiffness is primarily a measure of how well the wheel absorbs bumps from the surface on which it rolls. Lateral stiffness, especially of the front wheel influences the handling of the bicycle. Torsional, or tangential stiffness is a measure of how well the wheel transmits propulsive and braking forces, if applied at the hub, as in the case of hub or disc brakes. Several factors affect these stiffnesses to varying degrees. These include wheel radius, rim bending and torsional stiffness, number of spokes, spoke gauge, lacing pattern, hub stiffness, hub flange spacing, hub radius.{{cite web Too much spoke tension, however, can lead to catastrophic failure in the form of buckling.{{cite web ==See also==