Track bike
A track bike (also track machine ) is a racing bike for track races . It has no brakes, gears or freewheels and has a different frame geometry than road racing bikes.
Track bikes are basically designed according to the same construction principles that are also used for racing bikes for road racing, but some of them are more prominent: The focus is on the maneuverability of the rider on the bike - i.e. H. the wheel should react as immediately as possible to the driver's steering maneuvers.
Basic principles
The following basic principles apply to track bikes :
- Wheelbase: while road racing bikes already have a shorter wheelbase of 95–100 cm compared to conventional utility bikes, this is usually less than 95 cm for track bikes;
- Head tube angle: While road bikes aim for head tube angles between 72 and 74 degrees , track bikes have steeper head tubes with angles that are sometimes well above 74 degrees. The head tube angle influences the caster of a bicycle: the steeper the angle, the less the caster. Since the caster dampens the steering angle, a wheel with a high caster is slower, but more stable. Since this property is not desired in track cycling, the caster is kept low: the track bike is more agile due to the steeper head tube , but also more nervous in its straight line .
Specific construction principles and technical features of track bikes
While the aforementioned properties gradually differentiate the track bike from the road racing bike, track bikes have other special features:
- Bottom bracket : While road racing bikes have a significantly lowered bottom bracket compared to utility bikes, the bottom bracket on track bikes is again 3–5 cm higher to prevent the cranks from touching down in bends or during evasive maneuvers.
- Lack of gearshifts and brakes, rigid gear : In order to reduce the risk of falls at the high speed and tight conditions on the track, track bikes have neither freewheel nor brakes, the so-called rigid gear is mandatory, which is why they have no gearshift. The rigid gear means that you have to pedal continuously while driving. In order not to run into another driver, you swerve - especially to the right, because the railway crossing then immediately reduces your speed. In an emergency, the speed can also be "countered", i. H. Counter-holding with muscle power against the rotating pedal. Since the road traffic licensing regulations u. a. requires at least two brakes, the use of rail bikes without brakes on public roads in Germany is not allowed.
- Stiffness and weight: Track bikes have to withstand the special forces (above all acceleration, changes in direction and centrifugal forces in curves). For this reason, weight is not so important as stability.
- Tires: come exclusively 27- As Tires inches - tubulars used. They can be inflated more than the clincher tires known from normal bicycles and thus withstand greater loads. For safety reasons, tubular tires are prescribed by the UCI for track races.
- Axle width: In contrast to the standard axle width of 130 mm for normal racing bikes and 135 mm for mountain bikes , track bikes have an installation width reduced to 120 mm on the rear wheel due to the lack of a pinion set.
Position of the driver
The position of the rider is usually more bent on the track bike. In competition, it is often driven in the "lower link maintenance" . Because of the high pressure in the bends and in order to enable a more comfortable position of the hands on the handlebars while maintaining the lower links, many drivers turn the handlebar ends more downwards, so that inclinations of up to 45 degrees are often encountered compared to the usual 15 to 25 degrees inclination. It is also popular not to mount the saddle horizontally, but rather with the tip sloping downwards.
Because of the higher cadence and the shorter cranks used on the track, a saddle position 0.5 to 2 cm lower is often set.
Speed, gear ratio, cadence and crank length
Basically, there is a fixed relationship between the three variables of speed, gear ratio and cadence : the higher the speed, the higher the cadence with a constant ratio , the smaller the ratio, the higher the cadence at constant speed.
Both can be found on the train: higher speeds with consistently lower gear ratios. That is why the pedaling frequencies in track races are consistently higher at 110 to 170 bpm than on the road (85 bpm to 120 bpm - on the mountain even below 50). Higher gear ratios, which would allow a lower cadence, do not correspond to the performance structure of track competitions and inhibit the driver in his mobility during special driving maneuvers.
When assessing the effectiveness and appropriateness of a gear ratio, in addition to the nominal gear ratio as the numerical ratio of chainring to sprocket set, the crank length must also be taken into account. In addition to the translation and the speed, it also determines the contraction speed of the muscles. For example, a crank length of 180 mm with a gear ratio of 53/17 enables the same contraction speed and the same average effort as a crank length of 170 mm with a gear ratio of 53/18.
Whether one or the other of these two "equally large" translations is chosen depends on various framework conditions. These include:
- Height and build of the athlete
- Type of exercise: endurance exercise or sprint.
While longer cranks are preferred for endurance performances on the road or on the track, track sprinters use extremely short cranks because they want to move as far as possible in the strength-optimal range during the entire pedaling cycle. (E.g. Eddy Merckx chose a comparatively high gear ratio for his world hour record of 52/14, but also used cranks with 175 mm longer than is usual on the track with his body size.)
As in road racing, translation restrictions apply to the school, youth and junior classes .
Regulations
The UCI has defined exactly what track bikes should look like. The shape of time trial machines in track cycling is strictly prescribed for record rides such as the world hour record and largely corresponds to the technical status of the bikes that are used on the road in time trials. For example, Jens Voigt used a converted road time trial bike for his world hour record in autumn 2014. Disk wheels are common and approved, but are not used exclusively.
New trends
In the mid-1980s, New York bike couriers began using train bikes for their work on the streets of Manhattan. This trend also continued in European cities. Special shops, often in combination with bicycle courier services, offer converted racing bikes with a fixed gear ("fixies" from English: fixed gear) for use on the street. For this, however, brakes are not always installed, which makes the approval for public road traffic void. For some riders, it is enough to reduce the speed with muscle power on the rear wheel. So-called "track bikes" are also offered. These are mostly racing bikes without gears and brakes. In the meantime, however, there are special “road fixation frames” for a wide variety of purposes such as B. Courier bike or trick bike. However, apart from their external appearance, these bicycles have nothing to do with track bicycles; they are unsuitable for driving on the track and are prohibited.
Web links
Individual evidence
- ↑ bikecult.com
- ↑ WB Bahn ( Memento from February 4, 2016 in the Internet Archive ) (PDF; 567 kB) Federation of German Cyclists: Competition regulations for track racing, Section 4.3.2