Bicycle wheel

A wheel is defined as the whole of a front or rear wheel for bicycle. Sometimes a wheel is colloquially referred to as the rim or tire, although it is only talking about components of the impeller. What parts exactly the term impeller is not fixed and depends on external circumstances. In operation, ie in the race, the term always denotes a complete and production ready bike with the purchase of these wheels are supplied mostly without tire and tube, but with rim tape, without sprocket assembly and brake disc. All wheels of a bicycle are collectively referred to as wheelset.

Designs

Classic impeller

In a classic wheel all the items are standardized. Thereby can be used in assembling a wheel easily components from different manufacturers. All parts are available separately, so that defective parts can be easily replaced. In addition, all the tools are easy to obtain. A classic wheel consists of:

• Rim,
• Spokes and nipples
• Possibly washers for the spoke heads,
• Hub,
• Axis, often in the form of a quick release or thru axle,
• Tires with jacket ( also called blanket ), tube and rim tape or ( in tubular tires ) tires and rims adhesive ( mostly Rim, formerly tar band )
• One or more gears ( only on the rear wheel ) and
• Possibly brake disc.

The number of the spokes depends on the price of the impeller and on the intended use. Most common are wheels with 36 spokes, the less heavily loaded front wheel are also wheels with 32 spokes to be found. Modern mountain bike wheels sometimes have front and rear 32 or 28 spokes. Especially in the past were on tandems wheels spread with 40 or 48 spokes; with modern components are 36 spokes usually sufficient. Racing bikes have to reduce the weight and improve aerodynamics often substantially less than 36 spokes; on the front wheels are only 12 spokes possible.

For training on the road bike wheelsets classic 36 -hole rims are rarely used yet. In bicycle racing up in the 90s almost exclusively 28 -hole rims were used. In track cycling, however, was the 36 -hole rim standard, until they were replaced by other types.

Classic wheel with straight spokes

A variation of the classic wheel is one with straight spokes. To build up appropriate hubs and spokes are required, the rim, and any other components do not differ. The advantage is that the hubs are easier for straight spokes and the bending stress on the spokes arc omitted. Matching hubs and spokes are available from different manufacturers, so that defects are repairable.

System wheel

For system impellers individual manufacturers change the items and designs of impellers. Tire, tube and rim tape correspond to those classic wheels to ensure a choice and interchangeability.

Disseminated particular " reverse" built spokes, that is with the nipples on the hub rather than on the rim. This reduces the moment of inertia of the impeller and the air resistance, because the nipple on the hub move slower. These spokes are often straightened instead. The profile of the spokes of road bike wheels is usually oval or narrow diamond-shaped to reduce air resistance ( " spokes "). By a vote of the individual components to each other can reduce the number of spokes, sometimes only 12 spokes in the front wheel used. The spokes are usually made of solid steel, aluminum alloys rare and only in very few cases, such as expensive race wheels with carbon or aramid fibers (Kevlar ) reinforced plastics. As rim material is aluminum except increasingly carbon-fiber reinforced plastic ( "Carbon" ) are used.

The advantages of reduced air resistance are only released at about 40 km / h and thus only in the professional racing relevant and measurable; the benefits of a lower mass moment of inertia show through more efficient acceleration. System Wheels put in practice only in high-performance sports advantages, there they are not more widely used because of the lower stability of the asymmetrical lacing.

Although impellers have only a small attack surface for the wind, they play a large role in the aerodynamics of the bike. This is because that the upper side of an impeller to move at twice the speed of the driver or the front frame. That is, if a cyclist travels at 50 km / h, moves the top of its wheels with 100 km / h Since the power that is needed to overcome a given air resistance increases with the third power of the velocity, the drag coefficient (Cd value) is an eight times as strong.

The disadvantage of system wheels is that spare parts (except tires, tubes and rim tape ) are difficult or impossible to obtain, because it is not about standardized parts. Wheel repairs are therefore often possible only by the manufacturer.

Had the least number of spokes for years the Shamal wheelset Campagnolo with 12 spokes.

Disc Wheel

Especially for the time trial and for the Track Cycling Disc wheels are made. These reduce the air resistance and reduce turbulence. According to measurements in the wind tunnel they save compared to the normal 36 -spoke wheels at a speed of 40 km / h around 15 watts of power a. These wheels also have a tough ride.

Originally consisted of clad sheets spoke wheels disc wheels, later the covers were made ​​of stronger plastics. The current versions are laminated in predominantly leinwandgebundenem GRP or CFRP. In this manner, the disc acts as the spokes ( power transmission side stiffness). Disc wheels weigh between 1300 g ( for low-cost wheels ) and 1000 g In the world's lightest serial disc Lightweight 900 g were realized by the rovings ( carbon fiber bundles ) are only in the loaded direction. Disc wheels are very susceptible to crosswinds, which can specifically cause the front wheel to dangerous situations. In side winds that come at an angle of 60 ° from the rear, disc wheels, however, act like a sail and can additionally provide propulsion. However, the side wind is at an angle of 60 ° from the start, there occurs a substantial braking effect. Disc wheels can be noisy in bad ground. They are used primarily behind and are only allowed in the time trial at the UCI competitions. Disc wheels on the front are usually forbidden due to safety at the races UCI.

Special shapes

Three stores are impellers with three spokes. The aerodynamics is not quite as good as the disc wheel, but three stores are not susceptible to crosswinds. Three memories are often used as a front in the time trial. You count basically to the system wheels because they do not consist of standardized parts.

In simple mountain bikes and children's bikes sometimes find wheels use to be made ​​of one piece of plastic. This design has predominantly financial aspects. Such wheels are not repairable and can be found in the low range.

Size

Impellers are manufactured in different sizes, depending on the use and tradition.

Spoking

The basic step in the assembly of a wheel is about connecting the hub and rim with the spokes, known as the lacing. There are different types, depending on the use of the impeller and impeller taste of the manufacturer.

By far the most widespread is the tangential lacing pattern, in which the spokes are inclined in the impeller. Due to the inclination of the spokes can transfer torque, which is important when the impeller driven or a brake has in or on the hub ( drum, roller or disc brakes ). Thus, the impeller is stable in itself, the spokes must be alternately inclined forward or backward, resulting in a crossover of the spokes. The more oblique leave the spokes from the hub, the more torque it can transmit, and the more spokes cross each other. However, means a greater skew, longer spokes and thus a higher impeller mass. The most common is the triple junction, because they can be applied to impellers 24-36 spokes and already transmits a very large torque. The largest torque can be transmitted when the spokes go off tangent to the flange of the hub. Is at 24 with spokes of the triple, 36 spokes to the quadruple intersection and 40 spokes to the junction of the five-way case.

When Radialeinspeichung the spokes are straight from the hub to the rim. The advantage is the short length of the spoke and the correspondingly low mass the impeller and a slightly higher lateral stiffness. However, the hub flange is heavily loaded. Therefore, all hubs are not enabled for this Einspeichmethode. Because there is no torque can be transmitted, the radial lacing is only suitable for non-driven wheels without brake in or on the hub. Widespread she is in front racing wheels.

Less common are Sondereinspeichungen, like the pictured at the top of this article Campagnolo wheel. Some special Einspeichungen serve only aesthetic purposes, while others are designed to improve the function. Thus, occasionally, the sprocket - side tangentially spoked wheel when driven because it has to transmit torque, while the opposite side is radially spoked. Some special Einspeichungen lead to a strong load on the hub flange, so they are only useful with certain hubs. Among the special Einspeichungen include methods, hubs and rims with a different number of spoke holes to join.

The length of the spoke is calculated as follows:

• L = length of the spoke
• S = width hub flange
• Di = inner rim diameter
• D = diameter of the hub flange
• Nk = number of crossings