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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

New! On-line Gear Calculator for Internally-Geared Hubs

General information

Another article on this site covers maintenance issues that apply to 4-, 7-, 8- and 11-speed Shimano Nexus and Alfine 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 the 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 pawl. 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

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.

These hubs have gone through several minor design changes, resulting in new model numbers and parts incompatibilities. Most Nexus model numbers are in the form SG-8Rxx --: example, SG-8R20. The first digit after the "R" represents the series, reflecting the number of roller clutches and whether the hub has cable shifting or electrical shifting. The greatest compatibility is within each series.

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 be reflected in the design of the shell). See this Shimano document for description of some internal differences. I haven't had the opportunity to experiment, but I suspect that Alfine shells are largely compatible with parts for Nexus hubs that have three roller clutches, and vice versa.

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. Better lubrication than is provided at the factory is recommended -- even with a new hub -- to forestall this problem and to make 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 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.

Premium models have three roller clutches rather than only 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

All gear carrier units with pawls rather than a roller clutch at the left side are interchangeable, allowing upgrades. 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-C6010 and SG-C6060, needle bearings, also allowing upgrades. The SG-8R55 and SG-8R56 carrier units are interchangeable, and these are red-band hubs, but Shimano lists no gear carrier interchangeability of these with other models. Shimano does not document interchangeability between Nexus and Alfine models.

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

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

Shimano made information sheets available for earlier hubs individually. The tables below list models in each series of the 8-speed hubs in order from newest to oldest. The right-hand column holds links to available information, except for information common to many hubs and covered in the dealer's manuals. Shimano has provided rebuilding instructions for only one model, though others are similar.

Parts availability can be a concern, especially with older models. Most parts lists linked in the tables below include information on compatibility with other models, and are formatted similarly so that you can layer one over another on your computer screen and compare them visually (like an astronomer looking at two sky photos in a "blink comparison" when searching for an exploding star or an asteroid).

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

Model Features Documentation
Alfine SG7000 and SM-S7000 Three roller clutches, CenterLock rotor fitting. Mostly compatible with S501 but axle assembly and cassette joint are different. Parts list, exploded drawing
User Manual
Alfine SG-S505 Three roller clutches, CenterLock rotor fitting, electrical shifting. Most parts compatible with S501. Parts list, Exploded Drawing
User Manual
Alfine SG-S501 Three roller clutches, CenterLock rotor fitting; backwards-compatible with S500. Parts list, exploded drawing
Installation instructions

Alfine
SG-S500

Three roller clutches, CenterLock rotor fitting; mostly interchangeable with S501 Parts list, exploded drawing
Installation instructions
Alfine
WH-S501-8D
8-Speed rear wheel; three roller clutches, CenterLock rotor fitting Parts list, exploded drawing
Servicing instructions
Alfine
WH-S501-V-8D
8-Speed rear wheel; three roller clutches; CenterLock rotor fitting Parts list, exploded drawing
Alfine
WH-S500-8D
8-Speed rear wheel; three roller clutches;CenterLock rotor fitting. Parts list, exploded drawing
Installation instructions
Alfine
WH-S500-V-8D
8-Speed rear wheel; three roller clutches; CenterLock rotor fitting. Parts list, exploded drawing
Installation instructions

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Nexus 8-speed Freewheeling/Rollerbrake Models

Nexus
SG-C6060-8R
SG-6060-8V
Three roller clutches, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
User manual
Nexus
SG-C6010-8R,
SG-6010-8V
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
User manual
Nexus
SG-C6000-8R,
SG-6000-8V
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
User manual
Nexus
SG-8R60, SR-8R60-VS
Three roller clutches, Rollerbrake/brakeless, electrical shifting No parts list/ exploded drawing yet.
User manual
Nexus SG-8R56 Three roller clutches, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
Installation instructions
Installation of right-hand dustcap B
Nexus SG-8R55 Three roller clutches, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
Installation of right-hand dustcap B
Nexus SG-8R45 One external roller clutch, Rollerbrake/brakeless, electrical shifting Parts list, exploded drawing
Installation of right-hand dustcap B
Nexus
SG-8R36,
SG-8R36-VS
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
User manual
Nexus SG-8R35 Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Nexus
SG-8R31,
SG-8R31-VS
Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
User manual
Nexus SG-8R30 Three roller clutches, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Nexus SG-8R27 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Nexus SG-8R25 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Nexus SG-8R22 One external roller clutch, Rollerbrake/brakeless Parts list, exploded drawing
Installation instructions
Nexus 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
Nexus WH-8R25 8-Speed Rear Wheel; for rim brakes only; one external roller clutch Parts list, exploded drawing
Installation instructions

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Nexus 8-speed Coaster-Brake Models

Nexus
SG-C6060-8C
One external roller clutch, coaster brake, electrical shifting Parts list, exploded drawing
User manual
Nexus
SG-C6000-8C
One external roller clutch, coaster brake Parts list, exploded drawing
User manual
Nexus SG-8C56 One external roller clutch, coaster brake, electrical shifting Parts list, exploded drawing
Installation instructions
Nexus SG-8C45 One external roller clutch, coaster brake, electrical shifting Parts list, exploded drawing
Nexus SG-8C31 One external roller clutch, coaster brake Parts list, exploded drawing
Installation instructions
Coaster brake instructions
Nexus SG-8C22 One external roller clutch, coaster brake Parts list, exploded drawing
Nexus SG-8C20 One external roller clutch, coaster brake Parts list, exploded drawing.

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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 have a very nice 1970's Raleigh Competition racing frame which I converted into a Nexus 7-speed:

Sheldon Brown's Nexus Raleigh Competition

Sheldon Brown's Nexus Raleigh Competition

That worked out so nicely that 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. 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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