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Servicing Sturmey-Archer 8-Speed Hubs

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by John "Pieces of Eight" Allen
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Sturmey-Archer X-RD8(W) 8-speed hub

Cross-section of Sturmey-Archer X-RD8(W) 8-speed hub with drum-brake.

General information

Another article on this site covers topics common to many Sturmey-Archer hubs. Please read that article to learn about

There are also articles on this site more generally about

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Gearing

old English The 8-speed Sturmey-Archer hubs have an innovative, modular design with 3 planetary systems one after the other. If a module's sun gear is locked to the axle, it gears up, and if not, the module operates at unity ratio. Each of the three modules has a different ratio. The eight possible combinations offer eight different speeds.

Because these hubs only gear up, they require a much smaller chainwheel than other hubs and are especially well-suited to a small-wheel bicycle. These hubs are most efficient in the lowest gear, which passes power directly from the driver to the hub shell, and least efficient in the highest gear, which uses all three modules.

Model designations include the letter F, for freewheeling; K for disc brake and D for drum brake. The discontinued X-RR8 was available with a fitting for a Shimano Rollerbrake. There is no coaster-brake model.

The ratios for the wider-ratio series introduced in 2009 -- model X-RF8 (W) etc. -- are:

Ratio 1.000 1.303 1.481 1.677 1.931 2.186 2.485 3.239
Step 30% 14% 13% 15% 13% 14% 30%  

The ratios for the first series of 8-speed hubs -- X-RF8 etc. -- are:

Ratio 1.000 1.281 1.450 1.644 1.858 2.106 2.384 3.054
Step 28% 13% 13% 13% 13% 13% 28%  

These numbers are based on gear-tooth counts.

Also see Sheldon's Internal Gear Calculator.

It is difficult for a simple planetary system to achieve a non-unity ratio near unity, and so the bottom step is large with these hubs. To avoid a large jump in the middle of the range, the large jump is used again at the top of the range. For this reason, it is best to set the second-highest gear as the level-ground cruising gear, around 75 gear inches (6.0 meters development, 5.5 gain ratio). Setting any lower gear as the level-ground cruising gear would make the top gear too high to be useful. On the other hand, if you ride in flatlands so you don't need any very low gears, your might use a larger chainwheel or smaller sprocket to get more gears in the level-ground gear range.

There is more detailed information on sprockets and on setting the gear range on another page. Also see Sheldon's take on setting the gear range for this hub, on his 8-speed Raleigh Twenty page. Different (pedal) strokes for different folks...

Technical issues

A few technical issues are important when specifying, installing or rebuilding these hubs:

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Technical information on current models (2009-)

The new wide-ratio models are very similar to discontinued models, but a different tool is used to remove the screw-in right ball cup (though a brass punch also may be used, and obviously, many of the internal parts are different). Technical information with a parts list is available as of September, 2012 for the XRD8 (W).

Model Features Documentation
X-RF8 (W) No brake Mostly like X-RD8 (W).
Installation instructions
Video of operation
X-RK8 (W) Disk brake fitting Mostly like X-RD8 (W)
Installation instructions.
X-RD8 (W) Drum brake Installation instructions and parts list. Mostly like X-RD8

Technical information on discontinued models (ca. 2004-2009)

Technical documentation is available for these models.

Model Features Documentation
X-RF8 No brake Technical information
Installation
X-RK8 Disk brake fitting Like X-RF8
X-RD8 Drum brake

Technical information
Disassembly instructions from an owner.

X-RR8 Roller brake Like X-RF8

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Links

Sturmey-Archer logo
Official Site
old Sturmey-Archer logo Heritage site
Three-Speed Parts from Harris Cyclery
English Three Speeds, Care and Feeding
Internal-Gear Hubs
Sturmey-Archer Hubs, General Information
Sturmey-Archer 1902-1952
Sturmey-Archer 1935-38 Catalogues
Evolution of the Raleigh Sports
sheldon's 8-speed Raleigh Twenty
Sheldon's 8-speed Raleigh Twenty
John Allen's spreadsheets of internal-hub gear ratios
Martin Hanczyc's roadster pages.
Tony Hadland's Sturmey-Archer Pages
including the 1956 master catalogue with
rebuilding information for SWs
and others.
Hubstripping web site
Retro Raleighs
SW Hubs by Brian Hayes
Jane Thomas's site with
Sturmey-Archer service manuals.
Menotomy Vintage Bicycles
Chat forum on English bikes.

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