Bicycle hub
The bicycle hub is the center of a wheel. On a bicycle wheel, it rotates around an axle that is firmly clamped in the dropouts .
The essential components of a bicycle hub are the axle , bearings and hub housing. Depending on the design, the hub can be supplemented with additional elements such as brakes or freewheels . The hub shell are spokes attached.
In principle, a distinction is made between the front wheel hub and the rear wheel hub.
Front hub
The front hub can also be equipped with a hub dynamo and a hub brake . The usual installation width (hub width) is 90–92 or 100 mm, other dimensions are also used for special bicycles.
Rear hub
The main difference to the front hub is the ability to accommodate a sprocket or a set of sprockets , a larger installation width and a freewheel. In contrast to the front wheel hub , the hub brake (if available) can also be designed as a coaster brake.
There are a number of different designs. The most common are:
- Hub gear hub (also known as gear hub )
-
Derailleur hub
- Freewheel hub
- Cassette hub
Other designs are combinations of gear hubs and cassette hubs or special hubs for cycling such as. B. BMX . In the past, the entry-withdrawal hub was predominant. This type of hub is now only of marginal importance.
There are differences between the freewheel hub and the cassette hub: The more modern version is the cassette hub. In comparison to the freewheel hub, the axle bearing on the drive side can be positioned closer to the support ( dropout ). The result is less bending stress on the axis and consequently a reduction in the risk of breakage. This advantage is made possible by the fact that the right-hand bearing shell (or the corresponding bearing seat in the case of industrial bearings) does not sit relatively deep in the hub housing in the case of the cassette hub, but is part of the freewheel body screwed onto the hub on the right with a sleeve screw. As a result, the right axle bearing and freewheel mechanism swap their place in the broadest sense, which leads to a displacement of the bearing outwards. In the freewheel hub, the sprockets and freewheel form a unit, which is usually screwed directly onto the hub shell using a BSA thread (1.37 ″ × 24 threads per inch ). Freewheel hubs are also used on pedelecs with driven rear axles.
In the case of the cassette hub , the ring gear package is positively attached to the grooved freewheel body and fixed with a threaded locking ring. The specifications of the Shimano company have become the norm in practice . Only in the racing bike sector is there a competing factory standard from Campagnolo .
To assemble or dismantle the sprocket set , a sprocket pickup is required for the derailleur hub, and a chain whip to hold the sprockets when opening is required for cassette hubs. Depending on the manufacturer, this special tool is available in different versions, but in recent times the standards of the Shimano company have also been decisive here. Loosening freewheels that have been used for a long time can be force-consuming, because they tighten themselves very firmly due to the continuously transmitted torque when pedaling.
Dimensions
In terms of installation widths (distance between the dropouts), prevailing dimensions have become established in the course of the development of the bicycle, which are now considered to be the industry standard. This is 100 mm for the front wheel and 135 mm for the rear wheel, with the exception of the racing bike (racing bike: 130 mm). There may be deviations in gear hubs, folding bikes, special bikes such as B. tandems and almost always with historical bicycles.
The information in the lower part of the table all relate to the rear wheel:
| Installation width [mm] | Type | typical axle thread or diameter | typical axis length [mm] |
|---|---|---|---|
| 90-92 | simple front hubs | FG7.9 (5/16 ″ × 26TPI), rarely M7 × 1 or M8 × 1 | (105), 125 |
| 96 | rare with older front hubs | ||
| (98-) 100 | modern front hubs | FG7.9 (5/16 ″ × 26) or
M9x1 hollow axle with quick release |
|
| 108-110 | Front wheel: newer thru axles; Special wheels
Rear wheel: older wheels |
Thru axle Ø 15 or 20 mm
FG9.5 (3/8 ″ × 26), rarely 8.9 × 1 or M10 × 1 |
Rear wheel: 135-140 |
| 114 | 3–4-speed derailleur | FG9.5 (3/8 ″ × 26), rarely 8.9 × 1 or M10 × 1 | |
| 117-120 | 3-speed hub gear | FG9.5 or 13/32 ″ × 26 (~ 10.3 × 1) | |
| 120-124 | 3–5-speed derailleur; Track bikes with fixed hub | FG9.5 (3/8 ″ × 26), rarely 8.9 × 1 or M10 × 1 | 153 |
| 126-127 | Derailleur: older racing bikes 6–7-speed
Gear hub: up to 7 gears |
FG9.5 or M10 × 1 solid or hollow axle
FG9.5 or 13/32 ″ × 26 |
157, 165, 175, 185 |
| 130 | Derailleur gears: 7–11-speed racing bike, 7-speed mountain bike | FG9.5 or M10 × 1 solid or hollow axle | 173 or hollow axle 140 |
| 130-135 | newer hub gears | FG9.5 or M10 × 1 or 13/32 ″ × 26 | |
| 135 | Derailleur: Mountain bike 7-10 times | FG9.5 or M10 × 1 solid or hollow axle or thru axle Ø 12 mm | 178 or hollow axle 145 |
| 140-142 | modern mountain bikes; tandem | FG9.5 or M10 × 1 hollow axle; M12x1 or M12x1.5 as well as M12x1.75 thru-axle | |
| 145 | Tandem (newer models) | FG9.5 or M10 × 1 hollow axle | |
| 148 | modern mountain bikes "Boost" | M12x1 and M12x1.5 as well as M12x1.75 thru-axle | 172, 178, 180 |
| 150 | Downhill & freeride mountain bikes; Retro chopper | FG9.5 or M10 × 1 hollow axle | |
| 157-160 | Downhill & freeride mountain bikes; Tandem (Santana) | FG9.5 or M10 × 1 hollow axle | |
| 177 | Fat bikes | M12x1.5 or M12x1.75 thru-axle | 209 |
| 197 | Fat bikes | M12x1 or M12x1.5 as well as M12x1.75 thru-axle | 217, 229 |
- ↑ clear distance between the dropouts
- ↑ FG = bicycle thread according to DIN 79012
- ↑ TPI = threads per inch = threads per inch
- ↑ z. B. Singlespeed, track bikes, some hub gears before 1970 (Centrix or Shimano 3CC without spacer nut, GDR bikes with coaster hub)
- ↑ a b c older (torpedo) hub gears from Fichtel & Sachs and SRAM
- ↑ Full axle derailleur gears except Shimano
- ↑ Full axle Shimano derailleurs
- ↑ Full axle derailleur gears except Shimano
- ↑ Full axle Shimano derailleurs
- ↑ z. B. Hub gears from SRAM, Shimano Alfine & Nexus and Rohloff
- ↑ z. B. Shimano Alfine / Nexus 7- & 8-speed hub gears
- ↑ z. B. SRAM 9-speed and Rohloff hubs
- ↑ Full axle derailleur gears except Shimano
- ↑ Full axle Shimano derailleurs
- ↑ The previously common standard from 142 was increased to 148 in 2016 in order to be able to use wider tires without them coming too close to the chain.
axis
In addition to the traditional screw and quick release axles, thru axles with a diameter of 10 to 20 mm have recently been used on sporty bikes .
Axles are usually made of high-strength steel or titanium.
The axis length is determined by the installation width and the type of hub. With the common rear wheel installation width of 135 mm, the free axle length between the end pieces for quick release axles is 145 or 146 mm. Screw axles are 30–40 mm longer and protrude 15–20 mm on both sides, depending on the installation width, to accommodate washers and axle nuts.
In addition to metric threads with a thread pitch of 1 mm (or, as an exception, 1.5 mm) , traditional English inch sizes with a pitch of 26 tpi (tpi = threads per inch), which are slightly finer, are still widely used.
Screw axes
These are axles made of solid material that are more likely to be used with simple hubs. With the two axle nuts including washers, the axle is clamped with the inner rings of the bearings between the dropouts.
Axle diameter and thread front wheel:
- M7x1 - rare, for example on older GDR wheels
- 5/16 "× 26 or FG7.9 (7.9 × 0.98 mm) - The diameter can also be 7.7 mm , for example for GDR bikes
- M8x1 - the standard size
Axle diameter and thread rear wheel:
- 8.9 × 1 mm - for example DDR wheels
- 3/8 ″ x26 or FG9.5 (9.5 × 0.98 mm) - this is the most common size; There were rarely axles in this diameter with a coarser thread
- M10x1 - corresponds to the hollow axles from Shimano and was used, for example, on GDR bikes
- 13/32 "× 26 (10.32 × 0.98 mm)
Quick release axles
These are hollow axles through which a tie rod that can be tensioned by means of an eccentric is guided. The hollow axle should rest in the dropouts with a width of at least 3.5 mm, but less is usually not a problem in practice. In the tensioned state, a compressive force acts on the hollow axle. The axis compressed as a result becomes more resilient because the preload counteracts the tensile stress that is decisive for the load capacity (as a component of the bending stress). The compression of the hollow axle can also reduce the bearing play. This must be taken into account when setting the cones. The axis length is determined by the installation width and the type of hub. With the common rear wheel installation width of 135 mm, the axle length for quick release axles is 145 or 146 mm.
Axle diameter and thread front wheel:
- M9x1 - the standard size
- 9 × 26 (9 × 0.98 mm) - e.g. B. Campagnolo
Axle diameter and thread rear wheel:
- M10x1 - the usual size (e.g. Shimano)
- 10 × 26 (10 × 0.98 mm) - e.g. B. Campagnolo
Thru axles
Thru axles are primarily intended to improve the stiffness of suspension forks. Although the large-sized thru axles increase the weight of the hub, a suspension fork intended for use with thru axles can be constructed lighter, so that there is an overall weight advantage.
Thru axles are less sensitive to bending around the longitudinal axis, which occurs when lateral forces act on the bicycle tire while driving. While a rigid fork hardly allows the axle to be inclined, using a bicycle off-road with the less stiff suspension fork can result in the dip tubes deflecting unevenly or twisting against each other, so that the driving behavior becomes a bit spongy. The twisting of the tubes can also be caused by heavy braking with the disc brake, as the brake caliper stresses the bending of the immersion tube to which it is attached on one side.
Finally, there are concerns that the front wheel could be levered out of the dropout when using a disc brake (which is attached to the rear of the fork as usual) if the quick release has not been tightened enough or has loosened while riding. This would not be possible if a thru-axle axle was used.
The thru axle is usually clamped either with an Allen key or with the integrated quick-release lever. The latter are called QR20, QR15, QR12, QR10 or QR9 according to their outer diameter. QR stands for the English term quick release (Schnellspanner).
The front wheels of robust downhill mountain bikes have thru axles with an outer diameter of 20 mm. Otherwise, a diameter of 15 mm has prevailed for mountain bikes. Axles with a diameter of 12 mm and 9 mm are less common, although the former could possibly become the new standard for racing bikes. Axles with a diameter of 10 or 9 mm and installation widths of 135, 150 or 165 mm are usually used for the rear wheel.
Wheels with thru axles always require matching dropouts or axle mounts on the fork. Some hubs can be converted to different axle systems.
Thru-axle quick-release axles
A thru-axle thru axle is similar to a long screw bolt that has a short thread on one end and a screw head or quick release lever on the other end. There are also locking systems without threads, which only require a quarter turn to fix.
In the frame and fork of the bike, instead of the conventional dropouts, there is on the one hand a hole for inserting the axle and on the other hand an embedded threaded nut into which the thru-axle is screwed.
The thru axle often only fits into the associated frames or forks from the respective manufacturer. Third-party products must be specified explicitly for the respective system.
A hub from any manufacturer that is intended for use with a thru axle will usually fit if the diameter of the thru axle and the installation width match.
Thru-bolt thru axles
Thru-Bolt thru axles are similar in function to a standard quick release, but have a significantly larger outer diameter, so that they fit directly into the conventional dropouts used so far.
So far, the hollow axle has positioned the hub in the dropout and the quick release secured the hub against falling out by pressing the dropouts against the lock nuts. The new, larger-sized quick-release axles now take on both functions at the same time.
camp
The hub body is mounted on the axle with roller bearings . There must be at least two bearings.
The classic hub bearing is the design using a cone bearing. This consists of a bearing shell, balls (with 3/16 ″ or 1/4 ″ diameter), cone and lock nut. There is also a spacer washer or a spacer tube between the cone and the lock nut . The bearing play is set by moving the cones on the thread axis and fixed locks in the correct position.
A simple dust cover made of metal or plastic is usually available for sealing against dirt. This disk - sometimes also a cap - forms an annular gap either to the cone or to the hub housing. The sealing effect against ingress of foreign matter is lowest when the wheel is stationary.
So-called “industrial bearings” can also be used instead of conical bearings. These are, for example, commercially available deep groove ball bearings sealed with a shaft seal . Adjusting the bearing play is usually not possible or necessary here.
Hub shell / spoke flange
The central component of a bicycle hub is the hub housing. The material aluminum has almost completely replaced the sheet steel previously used. In addition to holding the bearings, the freewheel including the sprocket and other elements such as the hub brake or hub dynamo , the main function is to hold the spokes .
There are usually two spoke flanges on the hub shell. The spokes are inserted through holes in the spoke flanges. Depending on the design of the flanges, the spoke ends are curved or straight. 36 or 32 spokes are common, but significantly more or fewer spokes are possible.
Asymmetrical lacing: especially on wheels with derailleur hubs or disc brakes , the center of the rim is not on the center line between the two spoke flanges. The spokes on the drive side or, in the case of front wheels, the spokes on the brake side are therefore at a steeper angle to the hub axis and are also shorter. The stability of the impeller is reduced compared to an otherwise identical, but symmetrically spoked impeller.
Special spoke designs can also be riveted, screwed or glued to the hub. Another possibility is that the hub housing, spoke and rim form a single unit as a cast part made of light metal or plastic.
maintenance
The bearings must be re-greased depending on the version. A grease nipple can only be found on older models that were built into the 1970s. Exceptions are the hubs for track bikes from the Italian manufacturer Campagnolo and the XC-PRO hubs from the Japanese company Suntour, which were built from 1990 to 1994 . The Rohloff Speedhub 500/14 and the Shimano Alfine 11 are the only models on the market with oil bath lubrication .
A complete disassembly of the axle is therefore usually unavoidable for maintenance of the hub.
Divisible drive hub
With the divisible drive hub, the drive block is an independent component that is attached to the chain-side dropout independently of the hub body. This means that the sprocket and the chain can remain on the bike when the wheel is removed. Cinelli offered the Bivalent model in the 1960s . As a further special feature, the wheel part could also be used as a front wheel. In the 1990s, WECO manufactured divisible hubs (3BS Synchro). In contrast to the Cinelli hub, this was designed as a cassette hub. Divisible drive hubs have not established themselves on the market.
Manufacturer
The market for manufacturers of common hubs is now very clear. The market leaders Shimano and SRAM manufacture the majority of bicycle hubs for almost all types of bicycles. In addition, Quando is primarily active in the German market in the lower price segment. A number of manufacturers from France and Germany disappeared from the market in the late 1980s and 1990s. These include the manufacturers Maillard , Altenburger , Fichtel-Sachs , Weinmann , Sturmey-Archer (the name is used today by Sunrace) and others.
Shimano and Sturmey-Archer also build gear hubs . The German manufacturer Rohloff builds gear hubs in the higher price segment.
For racing bikes, Campagnolo , DT Swiss , Swiss Edco , Tune , Mavic (MTB and racing bike) and Fulcrum Wheels produce hubs in the higher price segment, mostly for their own system wheel sets .
For track bikes , singlespeeds and rigid wheels build u. a. the manufacturers Novatec , Phil Wood , White Industries , Halo , Dia-Compe and Miche special "track hubs" without freewheel. Stable hubs for BMX use are u. a. Made by Odyssey of California, Éclat and Halo.
literature
- Michael Gressmann, Franz Beck, Rüdiger Bellersheim: specialist knowledge of bicycle technology , European teaching aids, Haan-Gruiten 2006, ISBN 3-8085-2291-7
See also
Web links
Footnotes
- ↑ Dimensions at the fork failure at Fahrradmonteur.de
- ↑ see also the table at Radtechnik.awiki.org and Ralf Roletschek
- ↑ Detailed overview of the threads commonly used on bicycles by Ralf Roletschek
- ↑ Christian Artmann: What does the Boost standard bring? In: bike-magazin.de. November 29, 2016, accessed December 16, 2019 .
- ↑ Discussion of the introduction of thru axles for racing bikes in English on the website Cyclingtips.com, accessed in March 2016.
- ↑ Divisible hub from Cinelli. Retrieved April 1, 2015
- ↑ Company overview u. a. Taken from the Radspannereie website http://www.rad-spannerei.de/laufradbau-verbindungen.php