bike - Bicycle wheel
Photograph by Velo Steveon Flickr.
Other wheels (like those from Velomax/Easton) have a threaded hub shell that bike the spokes thread into. Some hubs have attachments for disc brakes or form an integral part of drum brakes. For information on other types of bicycle brakes see the full article on bicycle brake systems. The rear hubs have one or more methods bike Loveland Bike Trail for attaching a gear to it. The rim is commonly a metal extrusion that is butted into itself to form a hoop, though may also be a structure of carbon fiber composite, and was historically made of wood. However, on the rear wheel, because most bicycles accommodate a rear sprocket (or group of them), the dishing will often be asymmetrical: it will be dished at a deeper angle on the non-drive side than on the drive side. In addition to the three geometrical aspects of truing, the overall tension of the spokes is significant to the wheel s fatigue durability, stiffness, and ability to absorb shock.
In wheel design, reducing the rotational inertia has the benefit of more responsive, faster-accelerating wheels. The sealing fluid can also be added inside UST wheelsets to provide enhanced sealing capability in the event of thorn or spike punctures. “29-inch wheels”, which also conform to the popular 700C (622 mm diameter clincher wheel standard) are becoming more popular for not only cyclocross bikes but also cross-country mountain bikes for larger riders.
This is not always the case: for example if the hub used has harder, steel flanges like those on a vintage bicycle. Wheelbuilders also employ other exotic spoke lacing patterns (such as crow s foot , which is essentially a mix of radial and tangential lacing) as well as innovative hub geometries. However, to efficiently transfer torque from the hub to the rim, as with driven wheels or wheels with drum or disc brakes, durability dictates that spokes be mounted at an angle to the hub flange up to a tangential lacing pattern to achieve maximum torque capability (but minimum vertical wheel stiffness).
A nipple at the rim of a wheel usually protrudes from the rim towards the center of the wheel, but in racing wheels may be internal to the rim, offering a slight aerodynamic advantage. Butted spokes with reduced thickness of the spokes over the center section, are lighter, more elastic, and more aerodynamic than spokes of uniform thickness. The hub shell typically has 2 machined metal flanges to which spokes can be attached.
For most rim-brake bicycles, the dish will be symmetrical on the front wheel. A third alternative is titanium nipples, which are extremely strong, but substantially lighter than brass.
At constant speed, aerodynamics are a significant factor. If the inner part of the rim where the inner tube fits has spoke holes, they must be covered by a rim tape, usually rubber, cloth, or tough plastic, to protect the inner tube. An advantage of this system is that the inner tube can be easily accessed in the case of a leak to be patched or replaced. The ISO 5775-2 standard defines designations for bicycle rims.
Too much tension leads to overstressed spokes which have a short life. and thermoplastic. Rims designed for use with rim brakes provide a smooth parallel braking surface, while rims meant for use with disc brakes or hub brakes sometimes lack this surface. The Westwood rim is designed for use with rod-actuated brakes, which press against the inside surface of the rim.
Most bicycle hubs use steel or ceramic ball bearings. Vertical truing refers to adjustments of local deviations (known as hop) of the radius, the distance from the rim to the center of the hub.
Each flange has holes or slots to which spokes are affixed. The spokes still attach to the edge of the hub but not through visible holes.
More important, the rims must be heavier when there are fewer spokes, as the unsupported span between spokes is greater. The rest of the wheel remains approximately circular. Some authors conclude that the hub stands on those spokes immediately below it that experience a reduction in tension. 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.
A single eyelet reinforces the spoke hole much like a hollow rivet. Titanium spokes are softer and more expensive than steel, and aluminum spokes are less durable. Conventional metallic bicycle wheels for single rider bikes commonly have 28, 32 or 36 spokes, while wheels on tandems have as many as 40 or 48 spokes.
Older designs used cup and cone , whereas some modern wheels utilize pre-assembled 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. Most of these designs take advantage of new high-strength materials or manufacturing methods to improve wheel performance.
Thus it is generally preferred to build a crossed-spoke wheel where braking and drive forces are present. Some wheel designs also locate the spokes unequally into the rim, which requires a stiff rim hoop and correct tension of the spokes.
A spoked wheel with a disc cover may not be legal under UCI Union Cycliste Internationale rules because it is a non-structural fairing. 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. Bicycle wheels can be categorized by their primary use. For road bicycle racing performance there are several factors which are generally considered the most important: Semi-aerodynamic and aerodynamic wheelsets are now commonplace for road bicycles. The cogset (or cassette) on a rear wheel and disc brake rotors, if installed, take up width on the hub, and so the spoke flanges may not be located symmetrically about the center plane of the bike and wheel hub.
The common practice for minimizing wind-up in round spokes is to turn the nipple past the desired orientation by about a quarter turn, and then turn it back that quarter turn. In wheel truing, all these factors must be incrementally brought into balance against each other. The latter may be used for high-end aerodynamic racing wheels. Disc wheels are designed to minimize aerodynamic drag.
Road wheels may be designed for tubular or clincher tires, commonly referred to as 700C tires. Usually 20 inches in diameter (rim diameter of 406 mm), BMX (Bicycle Motocross) 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. Bicycle rims and tires came in many different types and sizes before efforts were made to standardize and improve wheel/tire compatibility. Universal System Tubeless (UST), originally developed by Mavic, Michelin and Hutchinson Some cyclists have avoided the price premium for a tubeless system by sealing the spoke holes with a special rim strip and then sealing the valve stem and bead seat with a latex sealer. The drawbacks to tubeless tires are that they are notorious for being harder to mount on the rim than clincher tires, In 2006, Shimano and Hutchinson introduced a tubeless system for road bikes. The rim is connected to the hub by several spokes under tension.
The average 29-inch mountain bike tire has an outside diameter of about 28.5 (724 mm). The lightest possible weight and optimum aerodynamic performance are beneficial for road bicycles, while for cyclo-cross strength gains importance, and for touring bicycles strength becomes even more important.
This is easiest to see with bladed or ovalized spokes, but occurs in round spokes as well. When forward torque is applied (i.e., during acceleration ), the trailing spokes experience a higher tension, while leading spokes are relieved, thus forcing the rim to rotate.
Some wheels (like the Full Speed Ahead RD-800) have an additional flange in the center of the hub. Their rim diameter of 622 mm (~24.5 inch) is identical to most road, hybrid and touring bicycle wheels but are typically reinforced for greater durability in off-road riding.
While braking, with leading spokes tighten and trailing spokes are relieved. See Bicycle performance for more detail. Tension spokes of modern bicycle wheels always are mounted so that the hub flanges are wider spaced than the spoke attachment at the rim.
In addition to elimination of rim strip and inner tube, the UST rim and tire combination allows the rider to run lower tire pressures for better traction and shock absorption without risking puncturing the tube in conventional bicycle tires. The axle can attach using a Modern bicycles have adopted standard axle spacing: the hubs of front wheels are generally 100 mm wide fork spacing, road wheels generally have a 130 mm wide rear wheel hub.
Conventionally laced 36- or 32-spoke wheels are most commonly built as a cross-3 or a cross-2, however other cross-numbers are also possible. Too little tension leads to a rim that is easily deformed by impact with rough terrain.
When a nipple turns, it twists the spoke at first, until there is enough torsional stress in the spoke to overcome the friction in the threads between the spoke and the nipple. A separate airtight inner tube enclosed by the rim supports the tire carcass and maintains the bead lock.
In 2007, Mavic introduced their R-Sys, a new bicycle spoke technology that allows the spokes to be loaded in both tension and compression. A pair is often called a wheelset, especially in the context of ready built off the shelf performance-oriented wheels. Bicycle wheels are typically designed to fit into the frame and fork via dropouts. 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.
Tables are available online which list tensions for each spoke length, either in terms of absolute physical tension, or notes on the musical scale which coincide with the approximate tension to which the spoke should be tuned. The typical 26-inch rim has a diameter of 559 mm (22.0 ) and an outside tire diameter of about 26.2 (665 mm).
Size 650B is 584 mm and 650A is 590 mm. Bladed and ovalized spokes may be held straight with an appropriate tool as the nipple is turned.
For example: In practice, most tires (and inner tubes) sold today carry apart from the modern ISO 5775-1 designation also some historic size markings, for which there exists no longer any officially maintained definition, but which are still widely used: Which designation is most popular varies with region and type of bicycle. Road Tubeless rims, like UST rims, have no spoke holes protruding to the air chamber of the rim.
When viewed in cross section, the spoke planes and hub form a triangular support shape for the rim, a structure that is stiff both vertically and laterally. This technology is promised to allow for fewer spokes, lower wheel weight and inertia, increased wheel stiffness, with no loss of durability. 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.
However this diameter of rim, identical in diameter to the 29er rim, is by far the most common on these styles of bicycles. To accelerate a wheel, total wheel mass matters less than the moment of inertia, which describes the inertial effect of the mass resisting acceleration (inertia) based on its location with respect to the axis of rotation (the center of the wheel hub/axle).
The former are commonly used for inexpensive BMX wheels and have a maximum tire pressure of 45 psi (3bars or atmospheres). The manufacturing tolerances, as well as seal quality, can be significantly superior to loose ball bearings.
The wider the hub flanges, the deeper the dishes, and the stronger the wheel can be laterally; but vertical stiffness will be low. A typical modern wheel has a metal hub, wire tension spokes and a metal or carbon fiber rim which holds a pneumatic rubber tire. A hub is the center part of a bicycle wheel.
A full disc is usually heavier than traditional spoked wheels, and can be difficult to handle when ridden with a cross wind. Lateral truing refers to elimination of local deviations of the rim to the left or right of center.
It should be noted that in the real world, a properly trued wheel will not, in general, have a uniform tension across all spokes, due to variation among the parts from which the wheel is made. Finally, for best, long-lasting results, spoke wind-up should be minimized. An increased number of all-carbon rims, such as Campagnolo Hyperon Ultra Clincher, Bontrager s Carbon Clincher wheels, DT Swiss RRC1250, and Lightweight Standard C wheelsets are now available. French tire manufacturer Hutchinson has introduced a tubeless wheel system, Road Tubeless, that shares many similarities to the UST (Universal System Tubeless) that was developed in conjunction with Mavic and Michelin.
The more vertical the spokes, shallower the dish, and the less stiff and strong the wheel will be laterally. A bicycle wheel is a wheel, most commonly a wire wheel, designed for a bicycle.
Hubs that have previously been laced in any other pattern should not be used for radial lacing, as the pits and dents created by the spokes can be the weak points along which the hub flange may break. These improvements have been made possible primarily through improved aluminium 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.
For all common tension-spoke wheels with crossed spokes, a torque applied to the hub will result in one half of the spokes - called leading spokes tensioned to drive the rim, while other half - trailing spokes are tensioned only to counteract the leading spokes. Kits such as those developed by Stan Koziatek (Stan s NotTubes) are available to convert non-UST bicycle wheels and tires to a tubeless configuration.
The angle at which the spoke interfaces the hub is not solely determined by the cross-number; spoke count, and hub diameter will lead to significantly different spoke angles. 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 inertial effect 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 use of aluminium nipples at the rim also reduces the moment of inertia, but they are less durable than brass. In addition to revised hub geometry, some rims have off-center drillings, and the mounting of common J-bend spokes at the hub flange can be altered inboard or outboard . .
Conventional wheels with spokes distributed evenly across the circumference of the rim are considered more durable and forgiving to poor maintenance. The 650C size has the ISO diameter size of 571 mm.
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. The rim provides a shallow circular outer cross section in which the tire lies instead of flanges on which tire beads seat. A tubeless tire system requires an air tight 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.
Thus, a wide range of small bike wheels are still found, ranging from 239 mm (12 inches) diameter to 400 mm (18 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.
Increasingly common are tubeless tires conforming to the UST (Universal System Tubeless) standard pioneered by French wheel manufacturer Mavic in conjunction with tire manufacturers Hutchinson and Michelin. These are called bladed spokes.
Off-road and mountain bikes have adopted a 135 mm rear hub width, which allows clearance to mount a brake disc on the hub or to increase the wheel dish for a more durable wheel. The bearings allow the hub shell (and the rest of the wheel parts) to rotate freely about the axle. A double eyelet is a cup that is riveted into both walls of a double-walled rim. Most bicycle rims are clincher rims for use with clincher tires.
It rolls more easily than smaller diameter tires. The wheel can thus transfer the hub torque in either direction with the least amount of change in spoke tension, allows the wheel to stay true while torque is applied. Wheels that are not required to transfer any significant amount of torque from the hub to the rim are often laced radially.
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. Various hook (also called crotchet ) designs emerged in the 1970s to hold the bead of the tire in place, allowing high (6–10 bar, 80–150 psi) air pressure. Some rims are designed for tubular tires which are torus shaped and attached to the rim with adhesive.
Thus since the rim must be centered but the hub flanges are not symmetric, there is a difference in dish between the left and right side of the wheel. It distinguishes between Traditional clincher rims were straight-sided.
To accomplish this, wheel designs are employing lighter rim materials, moving the spoke nipples to the hub or using lighter nipples such as aluminum. BMX bikes commonly have 36 or 48 spoke wheels.
Aluminum rims are still the most common, but carbon fiber is also becoming popular. Dish refers to the left-right centering of the plane of the rim between the lock nuts on the outside ends of the axle.
A spoke can connect the hub to the rim in a radial fashion, which creates the lightest and most vertically stiff wheel. Original bicycle wheels used wooden spokes that could be loaded only in compression, modern bicycle wheels almost exclusively use spokes than can only be loaded in tension.
For a dished wheel, the shallower dished side of the wheel (with more vertically aligned spokes) will have shorter and higher tensioned spokes than the deeper dished side spokes on the same wheel. These rims cannot be used with caliper rim brakes. The cross-section of a rim can have a wide range of geometry, each optimized for particular performance goals.
Aerodynamics, mass and inertia, stiffness, durability, tubeless tire compatibility, brake compatibility, and cost are all considerations. Aluminum rims are often reinforced with either single eyelets or double eyelets to distribute the stress of the spoke. 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.
In 3 dimensions, if the spokes were covered, they would form two cones ( dishes ). These rims are slightly larger in diameter than 700C ( 29er ) wheels and are non-compatible with bicycle frames and tires designed for the 700C standard. Children s bicycles are commonly sized primarily based on wheel diameter rather than seat tube length (along the rider s inseam) dimension.
Some wheels use both an aerodynamic carbon hoop bonded to an aluminum rim on which to mount conventional bicycle tires. Metallic bicycle rims are now normally made of aluminium alloy, although until the 1980s most bicycle rims - with the exception of those used on racing bicycles - were made of steel. Wheels with fewer spokes have an aerodynamic advantage, as the aerodynamic drag from the spokes is reduced.
The formerly popular 27 inch wheel size is now rare. A commonly recommended practice is to find the worst spot on the wheel, and bring it slightly more into true before moving on to the next worst spot on the wheel. Truing stands are mechanical devices for mounting wheels and truing them.
On the other hand, the reduced number of spokes results in a larger section of the rim being unsupported, necessitating stronger and often heavier rims. 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 refers to the pattern by which the spokes connect the hub to the rim.
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. The hub shell is the part of the hub to which the spokes (or disc structure) attach.
Names for various lacing patterns are commonly referenced to the number of spokes that any one spoke crosses. 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.
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. The axle is attached to dropouts on the fork or the frame. These tires have a wire or aramid (Kevlar) fiber bead that interlocks with flanges in the rim.
Stainless steel spokes are favored by most manufacturers and riders for their durability, stiffness, damage tolerance, and ease of maintenance. Several different techniques have been tried to minimize spoke cone asymmetry ( dish ).
Others (like the some from Bontrager and Zipp) do not have a noticeable flange. 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.
Spoke tensiometers are tools which measure the tension in a spoke. 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.
For climbing, total mass remains important. This system eliminates the need for a rim strip and inner tube. 26-inch clincher tires (with inner tubes) are the most common wheel size for off-road mountain bikes.
Smaller youth mountain bikes use 24 inch and newer off-road bikes for large riders have adopted heavy 700C 29 inch wheels. The nipple is usually located at the rim end of the spoke but on some wheels is at the hub end to move its weight closer to the axis of the wheel, reducing the moment of inertia.
This lacing pattern can not transfer torque as efficiently as tangential lacing. If a wheel is ridden with this torsional stress left in the spokes, they may untwist and cause the wheel to become out of true.
There are advantages and disadvantages associated with this change discussed in detail in the main article. Touring, race, and cyclo-cross bicycles may have vastly different design goals for their wheels. In the latter case carbon fiber is the material of choice.
The flange of the Road Tubeless rim is similar to the hook bead of a standard clincher rim but is contoured to very close tolerances to interlock with a Road Tubeless tire, creating an airtight seal between tire and rim. This is accomplished by using a special tape to seal any nipple holes in a standard rim and injecting a liquid latex compound into the tire before inflation.
Here, the spokes leave the hub at perpendicular to the axle and go straight to the rim, without crossing any other spokes - e.g., cross-0 . The dishes on each side of a wheel are not always equal.
While most manufacturers use the same lacing pattern on both left and right sides of a wheel, it is becoming increasingly common to find specialty wheels with different lacing patterns on each side. Some spokes are hollow tubes. The spokes on the vast majority of modern bicycle wheels are steel, stainless steel, titanium, aluminum, or carbon fiber.
This plane is itself determined as an average of local deviations in the lateral truing. It is also possible to true a wheel while it is mounted on the bike: brake pads or some other fixed point may be used as a reference mark, however this is less accurate. A wheel can be formed in one piece from a material such as thermoplastic (glass-filled nylon in this case) or carbon fiber.
A dishing gauge or truing stand can be used to measure the position of the rim relative to the hub. As with any structure, however, practical usefulness is not always agreed, and often wheel designs may be opted solely for aesthetic reasons. There are three aspects of wheel geometry which must be brought into adjustment in order to true a wheel.
The hub shell of spoked wheels generally have two flanges extending radially outward from the axle. Note however that rotational inertia is only a factor during acceleration (and deceleration/braking).
Both surfaces are smooth to allow the bearings to roll with little friction. Common vernacular calls an asymmetrically dished wheel simply a dished wheel.
The liquid latex fills the crevices and rubber voids of non-UST wheels and tires, creating an airtight seal. Wider touring or durable off-road tires require rims of 24 mm wide or more. 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 wheels, all else being equal, have higher rolling resistance than larger wheels. Rolling resistance also is reduced with increasing tire pressure, although the practical benefits become small at pressures significantly above 120 psi for the average bicycle rider. When a radial load is applied at the hub to a well tensioned wheel, such as by a rider sitting on a bicycle, it causes the wheel to flatten slightly near the ground contact area.
There are a few companies making wheels with spokes that are used in both compression and tension. At the end of each spoke is a specialized nut, called a nipple, which is used to adjust the tension in the spoke. It consists of an axle, bearings and a hub shell.
Another common method for making rough estimates of spoke tension involves plucking the spokes and listening to the musical tone of the vibrating spoke. For this reason, international cycling organizations often ban discs wheels or limit their use to the rear wheel of a bicycle. A disc wheel may simply be a fairing that clips onto a traditional, spoked wheel, addressing the drag that the spokes generate by covering them; or the disc can be integral to the wheel with no spokes inside.
Most adult mountain bikes use “26 inch” wheels.
