3-Speed Evolution

Firstly, apologies to those of you who’s interest in my blog was first piqued by the 3 speed hubs that I posted about – it’s been a long while since I’ve had anything tangible to write about. Unfortunately, I’ve struggled to find someone to do the machining work for me, but now that’s sorted I have a new, shiny hub to play with.
 
If you’re a regular reader of the blog then you can probably guess that this new hub is destined for the Full-Moto frame that I will be building later this month. I’m hoping that bike will also be running a belt drive and plus-sized tyres, so the big challenge with this hub was to ensure that I could achieve sufficient clearance past the rear tyre while maintaining a straight belt-line. This is something that the 44-ish millimetre chainline of my current hubs would struggle to achieve.
 
The answer to this little conundrum has come in the form of a CS-RK3. Yet another snappy hub name from Sturmey Archer, but this time it comes complete with an 8/9/10 speed cassette freehub body on one end. I’m guessing that Sturmey Archer’s intention is that this hub will be used in combination with a rear derailleur, with the hubs three internal gears being used to replace a front derailleur. However, with the use of a single speed spacer kit I can instead enjoy a whole heap of chainline adjustment to accommodate my belt drive and plus-sized tyres.
 
Having now rummaged around inside an S-RK3, an RS-RF3 and now a CS-RK3 hub, it’s interesting and heartening to see that Sturmey Archer are continuing to refine their hubs rather than rest on their laurels. Whereas the former two hubs contained a couple of plastic spacers and dust covers, this latest version is an all metal affair. They’ve even found a way to replace the fiddly thrust plate that used to rotate on the end of the driver assembly with a new mechanism that appears to be much more robust. The result of all these small improvements is that this latest hub easily feels the most solid and high quality Sturmey Archer hub that I have worked on.
 
The modifications that I have made to the hub are very similar to those that I have made to previous iterations. The two cup-and-cone axle bearings have been replaced with SKF cartridge bearings, while the larger ball-cage bearing that sits between the driver assembly and the ball ring has been replaced with an Enduro number (SKF don’t make a cartridge bearing in the right size). This modified hub is now silky smooth, something that I’m really pleased about.

As well as the higher quality internals, Sturmey Archer also import this hub into Europe in the 32 spoke hole version (unlike the other hubs that I have, which have always been limited to 36 holes). This opens up rim choice massively – something that was particularly important in this application given my desire for plus-sized tyres.

Because this particular hub is designed to run with a cassette, rear derailleur and associated shifter, Sturmey Archer have changed the cable pull of the hub so that it works with a Shimano front derailleur Rapidfire shifter. So, while this means that I am going to have to run the shifter on the ‘wrong’ / left side of the handlebars, it does mean that I can use a rather nice SLX i-Spec shifter that I can mount to my brake levers. With this shifter located where I would normally place my dropper post remote, I will also need to switch this to the other side of the ‘bars.

While my other hubs are all still running smoothly, I’ve got particularly high hopes for this latest iteration based on what I’ve seen so far. I can’t wait to get it slotted into my new frame to see how it performs. Hopefully I’ll be back in six months or so with an update on my initial thoughts.