Sturmey Archer AW Hub Overhaul: Curiouser and Curiouser

Rainy, dark winters are the perfect time to hunker down and disassemble something.  Since I’ve been wanting to know more about servicing SA 3 speed hubs, last winter I decided to take the plunge, having two potential candidates in my parts bins:  a 1974 model and one from 1978.

I knew I needed to do more than just endlessly stare at this parts schematic.  Fortunately, Glenn’s Complete Bicycle Manual dedicates 16 pages to the overhaul process.  And, I found especially helpful the online repair guides from Sutherland’s (courtesy of the Sheldon Brown site) and from Sturmey Archer (courtesy of Tony Hadland’s site).  The Sheldon Brown site also has detailed instructions as well as some helpful illustrations.

Before going down this rabbit hole, I also consulted several video guides and read a lot of interesting commentary regarding the “right” way to service these hubs.  RJ the Bike Guy’s video turned out to be the most practical and helpful.

First up was selecting which hub I wanted to overhaul.  I ended up choosing the earlier model due to its differently shaped slot on the “ball ring” which is a threaded part that connects the innards to the hub shell.  To loosen the ring you use a drift punch and hammer, then tap away counter-clockwise until the ball ring gives.  Unfortunately, newer models of the AW hub have ball ring slots which are more rounded and designed to take a proprietary spanner tool (which appears to no longer exist except perhaps in Wonderland).  After whacking away at the newer 1978 hub, I gave up and switched to the older 1974 model and had the ball ring loosened right away.  It’s also much easier to loosen the ball ring if you have a hub which is attached to a wheel.

But, before doing that you need to remove the outer nuts and washers and the cog which is held in place with a clip, as shown above.  Immediately after that you remove the left hand side locknut, washer, and cone, but leave the right hand assembly in place.  It’s important to keep all the parts in proper order as you remove them – I used zip-ties for this purpose.  It’s also important to note the orientation of all washers, and to make sure that the cog is re-installed correctly with its spacers and dished side as originally configured.

Once you unscrew the ball ring, the whole hub assembly comes out of the hub shell, intact.  Inside the hub shell you can see the ratchets at the bottom along with the left hand side set of bearings, held in a clip.   From there, you can remove the bearings from the left hand side of the hub shell (first you remove the “upside down dust cap”) and then set the hub shell aside.  Why are the dust caps upside down?  One site I consulted suggested that the troughs are meant to be filled with water proof grease, to further seal the hub from the elements.

After the driver is removed on the right hand side, which is done by removing the cone, the hub internals come apart in stages. The above photos document the series of steps to remove the clutch spring, gear ring, clutch assembly, and planet cage assembly.  You’ll note both the gear ring and the planet cage assembly have pawls.  The final photo above depicts the sun gear, which is permanently affixed to the axle.

For cleaning and reassembly, I found it easiest to tackle each sub-assembly separately.  The above photo shows, from top left to bottom right:  the planet cage, the clutch assembly, the driver, gear ring, and the ball ring.

The ball ring is aptly named – its a ring of ball bearings.  Studying the instructions gave me a lot of pause though, with confusing references to the ball ring having a “two thread start” and therefore meaning that in reassembly you might start the threading on a different thread than as it was originally threaded which could cause the wheel to be out of dish.  After doing a lot of reading about this, I came to the conclusion that this is of no importance to me, since my hub has no rim attached.

Unfortunately, at this point in my life I became very busy at work and didn’t get back to this project for many months!  When it came time for re-assembly, after having cleaned all the parts with a citrus cleaner, alcohol, and brass brush (I do not use toxic cleaners that can’t be safely disposed of), my brain needed a refresher course.  And, as I looked at the little planet gears I realized that I didn’t really properly understand how these hubs work, so I did some further research.

I found some answers by watching this interesting video, which depicts how the gears are engaged in this 3 speed hub. This is really different from how I thought these hubs worked.  I had imagined that each planetary gear circulating around the sun gear was of a different size (an idea I developed in childhood), and that’s what created the different gear ratios, much like a derailleur shifting through different sized cogs.  How wrong can you be!  Learning the importance of the clutch position has made me much more careful about shifting when I’m riding bikes equipped with internal hubs, remembering to lighten up on the pedals for each shift.

Meanwhile, back to the torture of the reassembly process:  things went fine until I tried to reassemble the pawls and pawl springs in the planet cage.  I dutifully lubricated the pins with Phil’s Tenacious Oil (as recommended by various mechanics), but when it came time to put the pawls and their tiny springs back in I had trouble getting them assembled correctly.  The pawl springs are so small that I actually “lost” them a few times only to realize that they were still right there on my work table, just basically invisible.  It’s also important to orient the pawls correctly, taking note of the slight beveling on one side.  I proceeded on with re-assembly, following carefully the instructions from Sutherland’s and from RJ the Bike Guy’s video.

After proceeding through the re-assembly of each of the subassembly, finally the hub is back together.  I was initially unhappy with the cone adjustment, which was a relatively easy fix.  The Sheldon Brown site has a good discussion of this process.  There should be a tiny bit of free-play in the hub if it is properly adjusted, and generally speaking, the adjustment should be made from the left hand side.  Once the cone adjustment was right, I also checked to see that the indicator spindle moved freely, so that the 3 gears can be engaged.  The true test will be to build the hub into a wheel and install it into a bike, but I’ll save that project for another rainy winter day.  And, now I will feel more confident overhauling the SA hubs on the two bikes I own which feature these hubs:  a 1950 Raleigh Sports Tourist, and a 1966 Sears/Puch.  I’ve gained a lot of useful knowledge and look forward to expanding on that.


4 thoughts on “Sturmey Archer AW Hub Overhaul: Curiouser and Curiouser

  1. Fun blog, and nice pictures, thanks!

    About the cone ajustment: I recommend adjusting it a bit tight so there’s no play while truing the wheel. Then back off the adjustment to allow free running after all truing, dishing, stress-relieving etc. are done.

    About the “upside-down” dust cap: it mates with a regular right-side up dustcap that’s attached to the cone, and together they form a labyrinth seal. Not really a seal, as water would pour in if you submerged it, but it prevents water splashed up from the road from getting in.

    About the double-start thread: I think you do still want it to start correctly, because it’s not just wheel dish it affects. If I’m thinking it through correctly (big if!) doing it wrong would also make the internal parts not line up as designed. The discrepancy would only be the difference between the two thread starts, which is what, a millimeter, 1.5 mm maybe? (Not looking at one right now) But if that caused less engagement on a wear surface, then it could affect durability.

    I’ve overhauled Sturmeys countless times, because at my first bikeshop job starting in ’71, we had a half-price winter overhaul deal, and a large fraction of the bikes that came in had AW hubs. As well as the occasional FW, SW, AM etc, some with the Dynohub built-in (AG). I got to where I claimed (without knowing if it was true) that I could overhaul one blindfolded. My bluff was called, money was laid down, so I had to try, and I did win the bet.

    That doesn’t mean I know what will happen if the double-start thread isn’t started right — on that I’m guessing, because I never tested it to find out. I just always assembled them correctly! We used to scribe a slight witness mark on the shell where the notch was before starting, and made sure the notch ended up in the same place when done. How I did that blindfolded I don’t recall, must have ‘clocked’ the wheel by noting the position of the valve stem, or some such… You can also *feel* the first and then second thread start as you insert it into the shell, if you know what to feel for. That would work blindfolded, maybe even better than with eyes open.

    I still keep an AW that’s assembled dry (no oil or grease) and just finger-tight, as a teaching tool to explain S-A hubs, but it’s been maybe 30 years since anyone asked me. But if anyone is in Seattle and wants to see an AW dis- and re-assembled, hit me up for a demo.

    Thanks again and keep ’em coming!
    Mark Bulgier

    • Thanks, Mark. I enjoyed reading your comments. I have to wonder about the purpose of the two thread start on the ball ring. It seems that since the ball ring could be installed in two different ways there had to be a reason! The cone adjustment/truing tip is helpful and thanks for the heads up on the mystery of the upside down dust caps.

  2. The “upside down dustcap” is a labyrinth seal, with the other half being friction-fit on the cone. A problem with using grease in an attempt to create a seal is that you get a “washing machine” effect, where grit sticks to the grease and then is carried into the bearing as the grease is agitated. The labyrinth seals work pretty well on their own.

    You can see the double thread in the close-up of the edge of the ball ring. The best approach on re-assembly is to apply very light pressure to the ball ring while turning it counter-clockwise until you feel the slight click that indicates that you have just passed the end of the thread. Then you carefully turn the ring clockwise to start the thread. In Schwinn Mechanics School this was called “catching the best leading thread,” and is a useful technique for any fine-pitch, large diameter thread, such as with bottom brackets, freewheels and track cogs. It is rare to find a bicycle part with a multiple-lead thread, but in the 3-speed hub it allows a fine pitch, which is stronger, while reducing the thread’s helix angle. This in turn reduces the tightening effect of the thread, making it easier to disassemble for service. I suspect that if they had used a single-lead thread, you would not be able to get it apart with a punch and hammer.

    When I was a young teen, I obtained a junk 3-speed wheel and took it apart to see how it worked. I was fascinated at the intricacy of the mechanism, and spent a lot of time studying it until I understood how it functioned. Unlike the watch I had previously disassembled, the hub could be put back together again! A couple years later, I stumbled across a field of discarded auto parts and decided to bring home a Ford automatic transmission to take apart. I was surprised to find large planetary gears inside, but it makes sense, as the gears are constantly in mesh, and the bands can be tightened around different components to change the output ratio when shifting. I’ve overhauled a wide variety of 2, 3, 4, and five speed internally-geared hubs and I’ve long been surprised by how they were considered “inferior” by most experienced cyclists, due to the types of bicycles they were installed on. That the manufacturers were able to keep the prices low on these complex mechanical marvels is impressive. On top of that, the essential design dates back to the late 1800s, with little substantial change since then! Like Mark, I got to the point where I could reassemble an AW hub with my eyes closed. The keys to making any internally-geared hub last is to keep it in adjustment, maintain its lubrication schedule, and ride it with respect.

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