Chainring
A chainring is the directly driven chain wheel of the chain transmission of a bicycle which is connected by the crank to the so-called spider . The number of chainrings depends on the type of gear shift and the model group of the bike , i.e. the area of application. Bicycles with a fixed gear ratio single- speed gear (fixie or single speed) have a chainring, bicycles with a hub gear , a bottom bracket gear or with a 12-speed or 13-speed sprocket package usually also have. Bicycles with a 9-speed, 10-speed or 11-speed sprocket package usually have two or three chainrings. The connection of several chainrings is called a chainring set .
Chainring size - gear ratio - drain length
In racing bikes , chainrings between 30 and 53 teeth are usually installed (with double sets usually 53 and 39 teeth). On mountain bikes with 9-speed, 10-speed and 11-speed sprocket packs, the chainrings often have 22, 32 and 44 teeth; on trekking bikes, 26, 36 and 48 teeth are a common combination. Recumbent bikes usually have gears with a large gear ratio range, so that mountain bike gears are often used here.
In the model group of mountain bikes and cyclocross bikes (or gravel bikes), so-called single drives have become popular in recent years. Only a chainring is installed here. This trend is made possible by the development of 12-speed and 13-speed cassettes. The pioneers in this area are SRAM and ROTOR. On mountain bikes, chainrings with 32, 34 or 36 teeth are installed in conjunction with a single crank. For gravel bikes, chainrings with 50 teeth are used in conjunction with the 13-speed ROTOR group.
The number of teeth of the rear sprocket, and that of the pinion , which determine the translation . It is particularly important to note that in bicycle technology the translation has always been calculated differently than in general mechanical engineering (reciprocal value). The decisive factor for the choice of chainrings and sprockets is not the translation, but the distance covered with one turn of the crank, which is called the development or expiration length . It is calculated from the circumference of the driven wheel and the translation.
Attachment to the crank
Cheap chainrings are permanently connected to the right crank and cannot be replaced separately. Otherwise, the chainrings are screwed to a crank spider, which is usually part of the crank. The crank star usually has four (mountain bike) or five (racing bike) mounting holes, to which two differently sized chainrings can be attached on both sides at the same time. The chainring bolts and nuts mostly have ISO fine threads M8 × 0.75. The larger one is mounted on the outside, the smaller on the inside. The imaginary circle on which all the fastening holes are located is called the bolt circle. There are several different bolt circles. Many crank stars have additional mounting holes for a third chainring (each with a significantly smaller bolt circle). The crank star is exchangeable for very high quality cranks.
Cranks for the front bottom bracket of tandems have an attachment on the left side for a single chainring, which holds the synchronous chain. The right crank is without a chainring. The rear bottom bracket for tandems has an ordinary crank for several chainrings on the right side, while the chainring for the synchronous chain is attached to the left crank.
Hole dimensions of the 5-arm cranks
| Crank type | Bolt circle diameter |
Hole distance |
smallest possible sheet |
|---|---|---|---|
| Racing bike "standard" | 130 mm | 76.4 mm | 38 teeth |
Road bike / MTB small blade with triple cranks , together with 110/130/135 mm |
74 mm | 43.5 mm | 24 teeth |
| Campagnolo (current) | 135 mm | 79.4 mm | 39 teeth |
| Compact crank , on racing and touring bikes and MTB standard until the early 1990s for large and medium-sized blades | 110 mm | 64.7 mm | 33 teeth |
| Campagnolo (before 1963) | 151 mm | 88.8 mm | 44 teeth |
| Campagnolo / Stronglight | 144 mm | 84.6 mm | 41 teeth |
| Stronglight 93 | 122 mm | 71.7 mm | 38 teeth |
| Ofmega, SR | 118 mm | 69.4 mm | 36 teeth |
| Campagnolo (old) | 116 mm | 68.2 mm | 35 teeth |
| Compact triple | 94 mm | 55.3 mm | 29 teeth |
| Shimano Dura-Ace (3-way, inner blade) | 92 mm | 53.3 mm | 30 teeth |
| Stronglight 99, Sugino | 86 mm | 50.6 mm | 28 teeth |
| MTB small sheet, together with 110/130/135 mm | 74 mm | 43.5 mm | 24 teeth |
| Microdrive Shimano | 58 mm | 34.1 mm | 20 teeth |
| Microdrive Suntour | 56 mm | 32.9 mm | 20 teeth |
The specified possible chainring sizes refer to series-produced chainrings. Larger chainrings in particular are available as custom-made products.
The so-called compact cranks are smaller and thus enable smaller chainrings than are possible with the common bolt circle standard of 130 mm. In the racing bike sector, compact cranks have attachment options for 2 chainrings, usually with a bolt circle of 110 mm. Compact cranks for mountain bikes with three chainrings usually have bolt circles of 94 and 58 or 104 and 64 mm (previously 110 and 74 mm), usually with chainrings with 22, 32 and 42 teeth (instead of the usual 28, 38 and 48 or 24, 36 and 46 teeth).
Hole dimensions of the 4-arm cranks
| Crank type | Outside bolt circle diameter |
Pitch circle diameter center |
Pitch circle diameter inside |
smallest sheet |
|---|---|---|---|---|
| MTB "standard" | 104 mm | 104 mm | 64 mm | 20 teeth |
| Shimano XTR until 2006 | 145 mm | 102 mm | 64 mm | 20 teeth |
material
Most chainrings are made of steel or duralumin ; chainrings made of titanium or carbon (with teeth made of aluminum or steel) are less common . They often have climbing aids . They should make it easier for the chain to switch between the chainrings when shifting. This mechanical peculiarity stands out due to the different dimensions of the individual teeth and different types of grinding on the tooth flanks.
Determination of the size (number of teeth) of the chainrings
The choice of the number of teeth of the two (three) chainrings in relation to each other and to the available sprockets (one speaks of a “sprocket set” or “cassette”) is very complex. Since the range of ratios of both chainrings overlaps, a solution has to be found in which as few of the “practicable” (see below) ratios as possible occur twice. "Passable" are translations where the chain skew is not too great - for this reason the two largest sprockets should not with the large chainring and the two smallest sprockets not with the small chainring.
For this reason, the so-called “step wreath” was used until the 1960s. In this variant, the gear ratios of the small chainring “grabbed” the gaps that were created by the 2-tooth gradation of the sprocket set when using the large chainring.
Today, on the other hand, sprocket sets are used in which the sprocket gradation has a difference of one tooth each and the range of ratios of the small chainring, neglecting the inoperable ratios, with a small overlap area, follows that of the large sprocket. For this reason, the chainring combination 53/39 is used almost exclusively in road racing today. With a sprocket cassette, which has, for example, the sprockets 11-12-13-14-15-16-17-18-19-21, the last possible gear ratio 53/18 with a gear ratio of 2 follows , 94 the gear ratio 39/14 with a quotient of 2.79 - in the overlap area are the gear ratios 53/19 and 39/14 with 2.789 and 2.786 and 53/18 and 39/13 with 2.94 and 3.00 respectively almost identical. The remaining overlap area is intentional because it avoids double shifting (chainring and sprocket change ) in certain racing situations.
Common translations in cycling
The following translations are common in cycling (here we are talking about the male adult area):
- Street, top amateurs and professionals: 53/13 in the flat; 53/18 to 53/15 on moderate inclines; Mountains: on short climbs, a higher gear ratio (up to 20% greater) is often used than on long mountains, therefore more or less binding information is only to be given for long climbs (passes etc.). The gear ratio depends on the amount of force used (the resulting cadence ) and speed. When traveling alone on an 8% incline, a rider who drives in the high-performance range (assumed 6.2 watts / kg; 430 watts) and achieves a good 21 km / h must achieve his (assumed) optimal cadence of 75 / min drive a gear ratio of 39/17. The example shows that there cannot be any schematic translation recommendations in this area. The “12er (53/12)” and “11er (53/11)” are also used for downhill runs and quick pursuits / attempts to break away.
- Track, top amateurs and professionals: 52/16, 53/16, and 52/15 in endurance competitions , up to 54/14 or 60/14 in competitions behind engines (Derny or Steher), 48/14 to 50/14 in sprinters .
In the youth classes there are translation restrictions that are usually fully exploited. The translations for women are mostly between those of the professionals and the juniors.
The myth of the "big leaf" in cycling
Both theories and legends have grown up around the use of the large chainring in cycling. These stem from the fact that the "big blade" is used at higher speeds and can therefore only be used by strong riders, especially when climbing. In his classic Tour der Leiden , Hans Blickensdörfer describes in great detail the moment when a famous cyclist on the mountain switches from the small to the large chainring and first has to “press” this translation.
In fact, there are serious physical reasons :
- Because of the higher moment of inertia of the chain and thus better synchronization, larger chainrings are used in endurance disciplines (road, rail from 4000 m ).
- When sprinting on the track, on the other hand, the smallest possible chainrings are used.
Everything else that is discussed in cycling circles about the large chainring can be traced back either to the myth or to certain common shifting practice (e.g. avoiding double shifting, see above). Expressions like “chain on the right!” (The big chainring is on the right), “leaving the big blade in there” etc. and the fact that many sprinters used to file out the number of teeth stamped in the chainring are testimony to the psychological factors involved play an important role.
The translation for mountain biking, the "little leaf"
A mountain bike often covers routes with a soft surface (sand, mud, etc.), which means that the rolling resistance is considerably higher than on asphalt. In addition, mountain bikes are usually heavier than racing bikes. For these reasons, mountain bikes have to be equipped with very small gears. When downhill on mountains without a lift, the particularly heavy downhill bikes must be driven up with a good mountain transmission. Therefore, the smallest chainring must not be too big.
In mountain races, a particularly large development area is desirable, because steep climbs can occur as well as elongated, flat passages or moderate descents, where additional “pressure” can be applied with a particularly large blade. However, mountain bike races are also won uphill rather than downhill.
Out of round chainrings
In the history of cycling there have been repeated attempts with non-circular, for example oval, chainrings. These have a different torque curve and should make the step more ergonomic. The best-known system is Biopace from Shimano that was popular in the 1980s. At the moment of the greatest pedaling force, i.e. with a horizontal crank, the radius was also reduced, i.e. the drive force increased. Conversely, at the moment of the lowest pedaling force, i.e. with the crank arms standing vertically, the radius was increased, i.e. the drive force was reduced. So, so to speak, Biopace reinforced the uneven torque curve. It has not caught on either in the consumer sector or in cycling.
Compared to those of the 1980s, today's oval chainrings have an oval that is shifted by approx. 80 ° in the direction of rotation , as it is assumed that this position is more likely to accommodate the force development favored by the physiology. Here it is so that in the moment of unfavorable crank position (vertical) the translation is reduced and vice versa. This is used to smooth the torque curve. None of the oval designs were able to establish themselves on the broad market, but there are some riders in professional cycling (e.g. Chris Froome and Bradley Wiggins ) who use these blades.
Individual evidence
- ↑ Marty Nothstein in an interview with Cyclingnews.com, accessed on March 29, 2011
- ↑ ROTOR Q-Rings vs. Biopace | ACS Distribution GmbH. Retrieved on May 28, 2018 (German).
- ↑ Why does Chris Froome use Osymetric chainrings and do they work? - Cycling Weekly . In: Cycling Weekly . March 16, 2017 ( cyclingweekly.com [accessed May 28, 2018]).
literature
- Rob van der Plas: The bicycle workshop - repair and maintenance step by step. 1st edition, BVA Bielefelder Verlaganstalt, Bielefeld, 1995, ISBN 3-87073-147-8 .
- Frank Lewerenz, Martin Kaindl, Tom Linthaler: Das Rennrad Technikbuch. 1st edition, Pietsch Verlag, Stuttgart, 2005, ISBN 3-613-50486-3 .
- Michael Gressmann, Franz Beck, Rüdiger Bellersheim: specialist knowledge of bicycle technology. 1st edition, Verlag Europa Lehrmittel, Haan-Gruiten, 2006, ISBN 3-8085-2291-7 .
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld, 1999, ISBN 3-87073-131-1 .