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Shimano Nexus and Alfine 8-Speed Hubs
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by Sheldon "All Fine with Me" Brown
revised by John "...Roku...Nana...Hachi" Allen
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Nexus Hub Cutaway

On-line Gear Calculator for Internally-Geared Hubs

General information

This article applies to Shimano 8-speed internal-gear hubs only. Another article on this site covers maintenance issues that apply generally to 4-, 7-, 8- and 11-speed Shimano internal-gear hubs:

There are also articles on this site more generally about

Read those articles along with this one. For more-detailed advice on installation of sprockets and setting the gear range, see the section on sprockets in the main article on internal-gear hubs.

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Gear range

Nexus is a family of parts, of which the Nexus Inter 8 eight speed hub is one. The Alfine 8-speed hub is a very similar, higher-end model which has a disc-brake fitting.

The overall range of the Shimano 8-speed hubs is 307%, and the steps in gears are a bit uneven:

Ratio 0.527 0.644 0.748 0.851 1.000 1.223 1.419 1.615
Step 22.3% 16.0% 13.9% 17.5% 22.3% 16.0% 13.9%  
 

For comparison, the Nexus 7-speed hub as a range of 244%, and the gear steps are more even:

Ratio 0.632 0.741 0.843 0.989 1.145 1.335 1.545
Step 17.3% 13.8% 17.3% 15.8% 16.6% 15.8%  
 

Click here for an On-line Gear Calculator for Internally-Geared Hubs

Does a hub need repair?

The Nexus 8-speed is more rugged than the 7-speed, but it has some well-known failure modes, and there are also well-known ways to prevent failure.

Aaron Goss, of Aaron's Bicycle Repair, reports:

A "clunk" now and again on a Shimano 8 speed hub is normal. It is the sun gear rotating and engaging the axle pawls. Even if you pedal lightly it will make that noise/feeling but not as loud. The harder you pedal during shifting or right after, the louder the noise. It can change as the hub gets older. Full cleaning and lubing usually restores like-new function but is expected that there will be slight differences in the noise over time.

Sometimes the shift spring on the axle can get weak or the axle sleeve that lifts the pawls can get sticky as it wears. I have solved the problem by replacing the axle unit or rebuilding it.

Care should be taken to release force on the pedals when shifting. Applying power to a pawl which is partly engaged can damage the pawl. Shock loads have also broken other parts of the axle assembly. Aaron has photos of axles showing typical failures. He also recommends not standing to pedal on hills. Instead, shift down and spin.

Probably the most common failure, though, is due to insufficient lubrication, leading to contamination by water and dirt.

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Installation and Rebuilding Instructions

(Links to instructions may be found at the end of this section)

The Shimano 8-speed hubs have a overlocknut spacing ranging of 132 to 135 mm, as sold: see Shimano's overlocknut spacing chart. It is possible to reduce the spacing of the Nexus Rollerbrake/freewheeling models to as little as 126 mm by leaving off the Rollerbrake and using a narrower locknut. See our Rollerbrake page for instructions. This is not possible with the coaster-brake or disc-brake models.

The internal mechanism of these hubs is complicated, and the usual repair is to replace the mechanism in its entirety. Shimano indicates little compatibility with hub shells of different models -- see the last two pages of this document -- but the internal mechanism can usually be replaced with a newer version as long as the hub is in the same series (with or without coaster brake; same number of roller clutches -- also be aware of other differences which may affect the design of the shell). See this Shimano document for description of some internal differences. You'll find details about interchangeability if you keep reading this page...

Shimano sells the axle assembly only as a unit and does not provide rebuilding instructions for it -- but you might disassemble it either by mistake or to cannibalize parts. Rebuilding instructions for the axle assembly are available on the Web site of Aaron's Bicycle Repair.

The right-hand hub bearing cup is vulnerable to damage from water contamination. Factory lubrication is inadequate, and better lubrication is advisable -- even with a new hub -- also, to make later cleaning and rebuilding easier.

The right-hand bearing cup is listed as a replaceable part in some parts lists. The old one would have to be extracted from the shell and a new one pressed in. If you succeed with this, please send advice, because that repair can save a wheel!

Do not lubricate the cassette joint (cable attachment parts): see advice in the Nexus technical article.

Basic models have a ratchet and pawls at the left side of the internal mechanism, and a roller clutch in the middle. Premium models have two or three roller clutches rather than only the one. These make only a very minor improvement in efficiency but are quieter than pawls and ratchets, and engage more quickly when resuming pedaling or changing gears. Coaster-brake models have at most one roller clutch.

A red band on the shell identifies a Nexus hub with needle-bearing pinions, for higher efficiency. The lower efficiency of 4th gear compared with the direct-drive 5th gear is noticeable on Nexus 8-speeds with plain-bearing pinions. Needle-bearing and plain-bearing pinions can be identified by their different appearance even in a fully-assembled gear-carrier unit.

plain-bearing pinions needle-bearing pinions

The SG-8R20, SG-8R22 and SG-8R31 have plain bearings; the SG-8R25, SG-8R27 and SG-8R45, needle bearings. Among models with a roller clutch at the left side, the SG-8R30, SG-8R31, SG-8R35 and SG-C6000 have plain bearings; the SG-8R36, SG-8R55, SG-8R56, SG-C6010 and SG-C6060, needle bearings.

A drag spring raises additional issues, and is even used in some models without coaster brakes, to improve engagement of roller clutches. Reader Bruce Dance indicates:

Drag springThe Alfine SG-S500-based models (hubs and wheelsets) have an 'A' and a 'B' version.  The 'A' versions are 'two-roller' internals, i.e. they use a pawl drive on the right-hand side (in 1-4) and the main (body center) roller clutch is preloaded by a drag spring that is set into the hub shell (as also found found in most of the coaster brake versions as well as Nexus hubs with pawl drive e.g., SG-8R25, SG-8R27).

(The image at the left shows the drag spring as it slips into the hub shell. The part number for the drag spring is the same for the Alfine as for some coaster brake hubs).

A difference in the SG-S500-A hubs (and some Nexus models) is that the roller retainer is castellated (has points which protrude to the left to engage the drag spring) whereas the SG-8R25, SG-8R27 (Rollerbrake/brakeless also, later coaster-brake and Alfine) hubs have no castellations on the roller retainer. Instead, there are protrusions on the carrier unit. The castellations, when present, are easily damaged.

A parts list for the SG-S500 'A' version formerly on the Paul Lange site (now in the Internet Archive) helpfully indicates compatibility with some Nexus 8 hub variants.

There is considerable compatibility between shells and internals provided the number of roller clutches is the same. However whilst you can usually fit a tension-spring preload clutch internal into one that was originally fitted with a drag spring, you do need to remove the drag spring. If you try to fit a drag-spring preload clutch internal into a hub shell that wasn't originally fitted with one, there usually is no place to fit the drag spring, and the centre clutch won't work reliably, perhaps at all.

Nexus and Alfine axlesWhile the axle assemblies are mostly identical, a section of the left end of the Alfine axle shown, as well as others, is fatter to withstand the bending moment from the optional disc brake, as shown in the image at the right (courtesy Aaron's Bike Repair). The Alfine left bearing cone threads onto the wider part of the axle. The Alfine requires a wider overlocknut distance than the Nexus without Rollerbrake. There are several different left-bearing-cone part numbers. Mix and match at your own risk.

The Rollerbrake and coaster brake are weatherproof, but drag slightly when not engaged, so if efficiency is a concern, avoid them. They also overheat when used on long downhill runs. We don't know for sure whether any coaster-brake model has needle-bearing pinions, but it appears not.

For all Nexus and Alfine 8-speed hubs except the S7000 series Alfine hubs, the cable is loosest in the lowest gear. The S7000 series is the opposite, and the cassette joint and axle assemblies are significantly different.

Bruce Dance sends the following warning:

It is very easy for parts (pawls or balls) to come adrift during assembly. For example commonly a ball (or balls) can come adrift from the ring bearing, either during assembly, or even in service (if the bearing adjustment slackens). This very often results in destruction of the hub internal, especially in the single or dual-roller hubs with a pawl-drive in the RHS, because the balls can easily get into where the pawls sit and then break them.

I therefore advise anyone working on these hubs to assemble the internal into the hub shell without the sprocket and the dust cover, and to be sure that all the balls are still present, and that the cone adjustment is pretty much done before the covers are refitted. Similarly if the hub has a pawl drive on the LHS (for gear 1 and 5), the internal ought to be rotated backwards as it is installed, else pawls may be dislodged.

I have seen one hub in which a roller came adrift (presumably during the factory assembly, since they cannot easily come out in service) and this smashed the hub shell to pieces. Kind of ugly.

Shimano has information on most but not all 8-speed models. These hubs have gone through several minor design changes, resulting in new model numbers and parts incompatibilities. Hubs parts numbers start with SG but there are also other parts listed, including brakes and shift levers. These pages are available in multiple languages, with a language list box at the upper right corner of the screen.

Several Shimano dealer's manuals offer information on installation, adjustment and maintenance of newer hubs:

Model numbers are of the form

Shimano made information sheets available individually for earlier hubs. The tables below list hubs in each series individually in order from newest to oldest, describing their differences, linking to information from various sources. The right-hand column holds links to available information, except for information common to many hubs and covered in dealer's manuals. Shimano has provided rebuilding instructions for only one model, though others are similar.

The tables below include Shimano's information on parts from older models which fit newer ones. To find which parts from neser models fit older ones, open the search function in your browser to look on this page for instances of an older hub's model number. Compatibility may cascade to yet another hub or hubs. At the small-parts level, there is much more interchangeability than is shown.

There is some interchangeability between Alfine and Nexus models. When a model number in the interchangeability column is in italics, the entire internal assembly is compatible.

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Alfine 8-speed (Disc brake/no brake) models

Model Features Documentation MU/Cassette Joint Interchangeability
SG-S7051-8 Electrical (Di2) shifting. Mostly compatible with SG-7001-8 but axle assembly and right-hand cone assembly are different.

Parts list, exploded drawing
User Manual

MU-S705 SG-7001-8
SG-S7001-8 Uses CJ-7000 cassette joint with cable entry above axle.

Parts list, exploded drawing
User Manual

CJ-S7000 SG-7000, SM-7000
SG-C6000-8D
SG-S7000-8 and SM-S7000 Mostly compatible with S501 but axle assembly and cassette joint are different. Parts list, exploded drawing
User Manual
CJ-S7000 SG-S501
SG-S505 Electrical (Di2) shifting. Most parts compatible with S501. Parts list, Exploded Drawing
User Manual
MU-S705 SG-S501
SG-S705 (11-speed)
SG-S501 Three roller clutches, fully-compatible with S500. Parts list, exploded drawing
Installation instructions
CJ-8S20 SG-S500

SG-S500

Two roller clutches (A type); three (B type). The A type has a drag spring and castellated roller-clutch assembly. See comments by Bruce Dance.) Parts list, exploded drawing (A type)
Parts list, exploded drawing (B type)
Installation instructions
CJ-8S20 A type: SG-8R20
SR-8R25
B type: A type,
SG-8R35, SG-8R30
WH-S501-8D 8-Speed rear wheel; three roller clutches Parts list, exploded drawing
Servicing instructions
CJ-8S20

WH-S500-8D (A type, B type), SG-S500 (B type)

WH-S501-V-8D 8-Speed rear wheel; three roller clutches Parts list, exploded drawing
CJ-8S20 WH-S500-V-8D (A type, B type), SG-8R35
WH-S500-8D 8-Speed rear wheel; two (A type) or three (B type) roller clutches. The A type has a drag spring and castellated roller-clutch assembly. See comments by Bruce Dance.) Parts list, exploded drawing (B type)
A type: see SG-S500
Installation instructions
CJ-8S20 WH-S500-V-8D (A type, B type), SG-8R35
WH-S500-V-8D 8-Speed rear wheel; two (A type) or three (B type) roller clutches. The A type has a drag spring and castellated roller-clutch assembly. See comments by Bruce Dance.) Parts list, exploded drawing (B type)
A type: see SG-S500
Installation instructions
CJ-8S20 WH-S500-V-8D (A type), SG-8R35

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Nexus 8-speed Freewheeling/Rollerbrake Models

Model Features Documentation MU/Cassette Joint Interchangeability
SG-C6061-8R, SG-6061-8V Electrical shifting, three roller clutches, Rollerbrake Parts list, exploded drawing
User manual
MU-S705

SG-C6060-8R
SG-C6010-8R

SG-C6061-8D Electrical shifting, three roller clutches, Shell appears to have Centerlock disc rotor fitting Parts list, exploded drawing
User manual
MU-S705 SG-C6060-8D
SG-C6060-8R
SG-6060-8V
Electrical shifting, three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
User manual
MU-S705 SG-C6010-8R
SG-C6000-8R

SG-C6060-8D
Electrical shifting, three roller clutches, Shell appears to be for band brake (?)/brakeless Parts list, exploded drawing
User manual
MU-S705

SG-C6060-8R
SG-C6000-8D
SG-S505


SG-C6011-8R,
SG-C6011-8V
Three roller clutches, Rollerbrake/brakeless. Parts list, exploded drawing
User manual
CJ-8S20 SG-C6010-8R
SG-C6000-8R
SG-C6000-8V

SG-C6010-8R,
SG-6010-8V
Three roller clutches, Rollerbrake/brakeless. Parts list, exploded drawing
User manual
CJ-8S20 SG-8R36
SG-8R31
SG-C6001-8D Three roller clutches, Band brake (? -- none shown in exploded drawing)/brakeless. Parts list, exploded drawing
User manual
CJ-8S20

SG-C6000-8D

SG-C6001-8R,
SG-6001-8V
Three roller clutches, Rollerbrake/brakeless. Entirely compatible with SG-6000-8R, SG-6000-8V and SG-6010-8R. Parts list, exploded drawing
User manual
CJ-8S20

SG-C6000-8R
SG-C6000-8V
SG-C6010-8R

SG-C6000-8D Three roller clutches, Band brake (? -- none shown in exploded drawing)/brakeless. Parts list, exploded drawing
User manual
CJ-8S20

SG-C6000-8R
SG-C6000-8V
SG-S7000-8

SG-C6000-8R,
SG-6000-8V
Three roller clutches, Rollerbrake/brakeless. Parts list, exploded drawing
User manual
CJ-8S20 SG-8R36
SG-8R31
SG-8R60, SR-8R60-VS Electrical shifting. Three roller clutches, Rollerbrake/brakeless No parts list/ exploded drawing!
User manual
MU-S705 No information
SG-8R56 Electrical shifting. Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Installation of right-hand dustcap B
MU-8S40 SG-8R55
SG-8R55 Three roller clutches, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
Installation of right-hand dustcap B
MU-8S40 SG-8R45
SG-8R45 One external roller clutch, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
Installation of right-hand dustcap B
MU-8S40

SG-8R25
SG-8R27

SG-8R36,
SG-8R36-VS
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
User manual
CJ-8S20

SG-8R35
SG-8R31

SG-8R35 Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
CJ-8S20

SG-8R25
SG-8R27
SG-8R30

SG-8R31,
SG-8R31-VS
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
User manual
CJ-8S20

SG-8R36
SG-8R35
SG-8R30

SG-8R30 Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
CJ-8S20

SG-8R35
SG-8R22
SG-8R20
SG-8C22
SG-8C20

SG-8R27 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
CJ-8S20

SG-8R25
SG-8R22
SG-8R20

SG-8R25 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
CJ-8S20 SG-8R27
SG-8R22
SG-8R20
SG-8R22 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
CJ-8S20 SG-8R27
SG-8R25

SG-8R20

SG-8R20 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
(and for the belt-drive version)
Installation instructions
Rebuilding instructions, from Shimano site
Rebuilding instructions, on this site
CJ-8S20 SG-8R27
SG-8R25

SG-8R22
WH-8R25 8-Speed Rear Wheel; for rim brakes only; one external roller clutch Parts list, exploded drawing
Installation instructions
CJ-8S20 None listed but similar to SG-8R22

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Nexus 8-speed Coaster-Brake Models

Model Features Documentation MU/Cassette Joint Interchangeability
SG-C6061-8CD Electrical shifting, one external roller clutch, coaster brake and disc brake rotor! Parts list, exploded drawing
User manual
MU-S705 None listed but probably compatible with SG-C6060-8CD
SG-C6061-8C Electrical shifting, one external roller clutch, coaster brake. Parts list, exploded drawing
User manual
MU-S705 SG-C6060-8C
SG-C6060-8CD Electrical shifting, one external roller clutch, coaster brake and disc brake rotor! Parts list, exploded drawing
User manual
MU-S705 SG-C6060-8C
SG-C6000-8CD
SG-C6060-8C Electrical shifting, one external roller clutch, coaster brake. Partial compatibility withSG-C6060-8R and SG-C6000-8C Parts list, exploded drawing
User manual
MU-S705 SG-C6000-8C
SG-C6060-8R
SG-C6001-8CD One external roller clutch, coaster brake and disc brake rotor! Parts list, exploded drawing
User manual
CJ-8S20 SG-C6060-8CD
SG-C6001-8C Electrical shifting, one external roller clutch, coaster brake. Parts list, exploded drawing
User manual
CJ-8S20 SG-C6000-8C
SG-C6000-8CD One external roller clutch, coaster brake and disc brake rotor! Parts list, exploded drawing
User manual
CJ-8S20 SG-C6000-8C
SG-C6000-8C One external roller clutch, coaster brake Parts list, exploded drawing
User manual
CJ-8S20

SG-8C31
SG-8C22
SG-8C20

Nexus SG-8C56 One external roller clutch, coaster brake, electrical shifting Parts list, exploded drawing
Installation instructions
MU-8S40 SG-8C45
Nexus SG-8C45 One external roller clutch, coaster brake, electrical shifting Parts list, exploded drawing MU-8S40 None listed but similar to SG-8C56
Nexus SG-8C31 One external roller clutch, coaster brake Parts list, exploded drawing
Installation instructions
Coaster brake instructions
CJ-8S20 SG-8C22
SG-8C20
Nexus SG-8C22 One external roller clutch, coaster brake Parts list, exploded drawing CJ-8S20 SG-8C20
Nexus SG-8C20 One external roller clutch, coaster brake Parts list, exploded drawing. CJ-8S20 None listed but probably compatible with SG-8C22

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Converting an Existing Bicycle

In some cases, it is possible to convert an existing bicycle to the use of a Nexus hub.

I converted my early '70s Raleigh International, using a Nexus 8-speed.
I like the Nexus 8-speed a lot better than the 7-speed version.

Sheldon Brown's Nexus Raleigh International

Sheldon Brown's Nexus Raleigh International

Ideally, the frame should have a dropout spacing of 127 to 135 mm to fit one of the Nexus hubs. Older bicycles are typically narrower than that. In the case of steel (Cromoly) frames, it is usually possible to spread the rear triangle to the needed width. Any good bicycle mechanic will be able to do this, or you can do it yourself.

If you leave off the Rollerbrake ®, you can get the spacing down to about 126 mm, as already mentioned. This is what I did on my Nexus bike. The Rollerbrake ® is a separate module, and when you buy the hub it is not even installed. (The brake unit would get in the way of fitting the spokes through the hub flange, so it has to be installed after the wheel has been built.)

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Links:

Shimano technical information pages

Shimano Tech Tips -- older pages: structure and function, troubleshooting charts etc.

nexus-greases
Shimano Nexus lubricants.
Harris Cyclery carries Nexus-equipped bicycles
from several manufacturers, including:

Breezer Bicycles

Aaron's Bicycle Repair, Seattle, Washington, USA -- specializes in internal hubs

Hubs to upgrade existing bikes

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