Bicycle wheel#Hub

The hub is the center of a wheel, which rotates about a fixed clamped into the lower leg axis at the wheel of a bicycle.

The essential components of a bicycle hub axle are, bearings and hub shell. Depending on the version, the hub may be supplemented with additional elements such as brake or freewheel. The hub shell, the spoke to be fixed.

The system distinguishes between the front wheel hub and rear hub.

Front Hub

The front hub can also be equipped even with a hub dynamo and a hub brake. The usual installation width ( hub width ) is 90-92 or 100 mm, find special bicycles Other measures application.

Rear Hub

The main difference is the front wheel hub of accommodating a gear or a sprocket assembly, a larger pave width and a freewheel. In contrast to the front hub, the hub brake - if any - are designed as coaster brake.

There are a number of different embodiments which are common:

• Nabenschaltungsnabe ( also referred to as hub transmission )
• Kettenschaltungsnabe Schraubkranznabe
• Cassette

More designs are combinations of gear hub and cassette hub or special hub for cycling sports such as BMX. Predominant was once the input - coaster brake. This hub design is now only to a marginal significance.

Difference between Schraubkranznabe and Cassette: The modern version is the cassette hub. Can here - compared to Schraubkranznabe - the drive-side axle bearing closer to the support ( dropout ) are positioned. The consequence is a lower stress on the axle and, consequently, a reduction in the risk of breakage. This advantage is made possible by the fact that the freewheel is a part of the hub. In Schraubkranznabe this is not the case. This form freewheel and freewheel a unit that wird.b screwed most by a BSA - threading ( 1.37 "x 24 speeds ) on the hub Schraubkranznaben also be used in pedelec with driven rear axle.

When the cassette hub sprocket assembly is attached to the form-fitting grooved freewheel and fixed with a threaded locking ring. As standard, the specifications of the company Shimano have prevailed in practice. Only in the racing area there is a competing company standard of Campagnolo.

For assembly / disassembly of the gear package a chain wrench is required when Kettenschaltungsnabe. Depending on the manufacturer, there is this special tool in different designs, but also the standards of the Company Shimano prevail.

The figures in the lower part of the table all refer to the rear wheel:

M7x1 M8x1 or

M9x1 hollow axle with quick release

Rear: older wheels [note 3]

FG9, 5 ( 3/8 " x 26), often 8.9 or x1 M10x1

Rear: 140

Hub gear to 7 -course

FG9, 5 or 13/32 "× 26 [ Note 4 ]

[Note 9]

Axis

The most common versions are Schraubachsen and quick-release axles. But other versions - like a thru-axle - are possible.

The shaft length is determined by the overall width and the type of hub. In the standard rear - installation width of 135 mm, the free shaft length between the end pieces with quick-release axles 145 or 146 mm. Schraubachsen are 30 mm longer and stand on either side depending on the installation width 15-20 mm in order to include washers and axle nuts.

The axis is usually made from high-strength steel.

Screw axis: This is a solid axle that is present in rather a simple hub. Means of the two axle nuts with washers is clamped the wheel hub between the dropouts.

Schraubachsen often have a shaft diameter of 3 /8 " (about 9.5 mm) with a thread pitch of 26 tpi ( tpi = threads per inch = pitches per inch), which is slightly finer than the pitch of 1 mm of DIN thread.

Quick release axle: This is a hollow shaft through which one can be stressed by means of eccentric tie rod out. The hollow axis should rest with at least 3.5 mm width in the dropouts, less is in practice usually not a problem in the tensioned state acts on the hollow axle, a compressive force. The resulting compressed axis becomes more resilient because the bias of the events relevant to the load tension counteracts ( as a component of bending stress ). The compression of the hollow shaft can also reduce the bearing clearance. This must be considered when setting the cones. The shaft length is determined by the overall width and the type of hub. In the standard rear - installation width of 135 mm, the axial length is at quick-release axles 145 or 146 mm.

A conventional rear axle diameter is 10 mm, with right-hand thread M 10 x 1 at both ends.

Thru-axle:

I thru-axle, the frame or fork with a system form (English Thru Axle )

The thru-axle itself usually fits only in the appropriate frame or forks of the respective manufacturer. Third-party products must be explicitly specified for the respective system.

The hub of any manufacturer, which is intended for use with thru-axle, fits a rule, if the diameter of the wheel spindle and the installation width match.

II quick-release axles, which are used instead of screw or quick release axle on conventional framework (English thru bolt )

Diameter and length of the stub axles corresponds to the dimensions of the usual mountain bike quick-release axles, so they should can be used in most modern frame.

Stock

The hub body is supported with bearings on the axis. At least two bearings must be present.

The classic hub bearing is the execution by means of cone bearing. It consists of bearing cup, balls ( 3/16 "or 1/ 4" diameter ), cone and locknut. Between cone and locknut is still a spacer or a spacer tube. Bearing clearance is adjusted by moving the cone on the axis.

Usually a simple dust disk of metal or plastic is available for sealing against dirt. This disc - sometimes a cap - either forms the conus and the hub body an annular gap. The sealing effect against invading foreign substances is lowest during standstill of the wheel.

Instead of cone bearings can also be used so-called " industrial warehouse ". These are for example commercially available, sealed with shaft seal ball bearings. An adjustment of bearing play is usually not necessary here.

Hub shell / spoke flange

A central component of a bicycle hub is the hub shell. The material aluminum has almost completely replaced the sheet steel used previously here. In addition to receiving the bearing, together with the freewheel sprocket and other elements such as brake hub or hub dynamo, the main function is the recording of the spokes.

Normally, two spoke flanges on the hub body are present. Through bores in the Speichenflanschen the spokes are inserted. Depending on the design of the flanges, the spoke heads are bent or straight. Are usual 36 or 32 spokes, but also significantly more or less spokes are possible.

Asymmetrical Lacing: the center of the rim is not on the center line between the two Speichenflanschen Especially with impellers with derailleur hub or disc brake. The drive side, or on the front wheels, the brake -side spoke therefore are at a steeper angle to the hub axis and is shorter. The stability of the impeller is thus reduced compared to an otherwise identical but symmetrical eingespeichtem impeller.

Special spokes versions can be riveted, screwed or glued to the hub. Another possibility is that the hub shell, spoke and rim form a casting of light metal or plastic a single unit.

Maintenance

The bearings must - depending on model - be greased. A grease nipple is, however, found almost exclusively in older models that were built up in the 1970s. Exceptions are, among others, the hub for rail wheels of the Italian manufacturer Campagnolo and the 1990 built until 1994 XC -PRO - hub of the Japanese company Suntour. The Rohloff 500/14 and the Shimano Alfine 11 have the only models on the market with oil bath lubrication.

A complete disassembly of the axis is therefore the maintenance of the hub usually unavoidable.