1simplexnut

Hi ,
Got a pile of new old stock Sturmey archer stuff .
In amongst it was a RK3 HUB .
I was trying to figure out what was the point of having a 3 speed internal then having an 8 speed derailleur set up ?
I have built up a wheel with an 8 speed IGH ( RK8) which I like on a clunker I have because of the simplicity , but I cannot see a good reason for the RK3 hub.
What am I missing ?

bwilli88 

Still 2 shifters, but only one acting on the chain. This makes for a simpler chain line; it can be used with a Narrow/Wide chainring.
I would love to try out a setup like that some day.

amedias

Also used on 'unconventional bikes' where fitting a front derailleur would be problematic but you still want a full gear range, ie:

- recumbents
- small wheel folders
- tricycles (some types are not conducive to FD fitting)
- some cargo bikes
- handcycles

And they can also be super useful on things like heavy haulers, big cargo trikes and rickshaws where you need crawler gears to get moving or deal with inclines and the ability to make a large shift when stopped as it's not always possible to manage a pre-emptive front shift in time.

They're a niche item for sure but where they are useful they are a fantastic option with few alternatives.

Bianchigirll 

I think it’s cool. With a FD you could have 72 gears and if you add a quad adapter……

markk900

Wouldn't gear freaking become quite an activity? It seems to me the standard -25%/direct/+33% of the 3 speed will result in a LOT of overlap gears with the 8 or 9 speed cassette, given the differences between rear sprockets are already fairly minimal. For example using a rear 18T cog in direct drive would yield an effective 23T in low and a 12T in high, yet on the SRAM 9 speed I used for comparison there is already an 12T and a 24T cog on the cassette. Seems like a lot of complexity for a small advantage!

wesmamyke

Basically the same thing as the old SRAM/SACHS dual drive. Came stock on Bike-E recumbents, at least one Cannondale hybrid I can think of. With the Cannondale I think it was just to get rid of that scary front derailleur though.

tcs

Fun fact: Sturmey-Archer has offered various IGH+derailleur gearing sets since the 1930s.

tcs

So let's take that Sturmey-Archer CS-RK3 with its HG splined driver, set the bike up 1x and slip on a SRAM Eagle 10-50T, 12-speed cassette:

tcs

How about a decent touring spread with fine graduations and a fast-shifting short cage derailleur?

tcs

You've always lusted after a straight block cassette, but your legs say 'no'.

cudak888 

The 8-speed Sturmey IGH hubs are geared for small wheel bikes. Requires a very small front ring otherwise and their reputation for reliability varies depending who you ask.

On the other hand, 3-speeds make for robust, simple, and price-conscious IGHs built around the SRF-3 architecture, which is basically the AW NIG from the 1980's. Good for the sales floor, and also good for many casual riders.

Try riding a derailer bike in a crowded city with multiple start-stops and in full business attire. They can't be shifted when stopped, get bashed up pretty quick in the bike racks, and the moving chainline ensures you can't have a full chaincase (with exception to very specific designs - Gazelle made one with an inverted RD in a chaincase). An IGH is preferable in these cases.

-Kurt

base2 

It's so that you can have the range of a triple on your 1x. An 11 speed mountain cassette will fit because the freehub body is 8,9,10 speed road.

The caveat is the rating says "34 tooth big cog" maximum. That's because it is not intended for mountain bike DH, AM, Enduro use. It's meant for road use & road cranksets are usually 50/34.

Thinking on this a minute: What they mean is it's rated for a 1:1 drive ratio.

Since gravel roads are still roads...
I have one with an 11-42 cassette mated to a 42 tooth Absolute Black narrow/wide chainring. The result on a 700x38 tire/rim is 20.7 to 140 gear inches. That's 678% range on a bike that would otherwise be limited to 1x

Low is low is low. 1:1 is 1:1 no matter how you get there. With an 11-28, 11-32, 11-42 cassette, whatever, still yields the same 20.7 gear inches at 1:1. It's just that the bigger spreads allow for bigger chainrings & thus higher top end speed.

I've never used the 11/42 while in overdrive. It's good to know that I'll never have to junk a cassette on account of the 11 & 13 tooth cogs being worn out.

Moe Zhoost

I count at least 14 overlaps on that combination. That still leaves 22 gears, but the logical shifting sequence would give the rider 17 gears. Personally, I would opt for a closer ratio cassette and probably an 8, 9, or 10; however it's real easy to get into the overthinking mode and waste too much time on stuff like this. I think I'll save up for a Rohloff.

tcs

Not so; they're just 'geared'.

When Sturmey debuted this hub at Interbike in 2009, they displayed it on a full-sized wheel bike:



Do you have to match the primary drive ratio to the gearing range you want? Uh, yeah, you know, like 1xs and 29ers?

I've been riding my XRK8 on a bike with 650 wheels since the fall of 2009. Great hub. It's relatively simple inside and relatively easy to take apart and re-grease, unlike the Nexus/Alfine 8 (Take an SG-S7001-8 apart? Are you mad? Just dunk it in oil and let it leak. )

Since the success of the Sturmey 8, Shimano has introduced a couple of IGH models with direct drive on the lowest gear, also intended for bikes of any wheel size.

cudak888 

Fair enough, I stand corrected.

Heck, I've put an XRF8 hub in a 26" rim with a 28t crankset too, though IIRC (don't remember off the top of my head), I remember reading something about torque limits of that hub.

FYI, I've had a Nexus 8 apart (SG-C6011-8R). It's complicated, but not impossible.

-Kurt

1simplexnut

Ah thats interesting . Thought I might have been pushing the limits with my build ,but apparently not so .


fugly as ! 25t rear 30 t front

1simplexnut

thanks for the input everybody .
Certainly seems I have plenty of options for a build with this hub .
72 gears sounds like a giggle .

Glennfordx4

I had one on a Hybrid and really liked it, it was a flip bike & figured I come across another one someday but it's been awhile and I haven't so I'm still waiting lol.

Velo Mule

I like hybrid gearing. That is the term that is often applied to an IGH with a derailleur. I know some have called it the worst of each system, but I don't agree. I can drop to the lowest IHG easily at anytime including stopped. And then I have the fine adjustments of the derailleur.

I haven't tried a three speed with a cassette, I think that would be fun to try. My preference so far has been old AW hubs with two cogs. This is half step gearing that provides six usable speeds. Three teeth difference between the two cogs and you can easily turn a 3 speed into a 6 speed. One more bonus, this is index shifting. Three indexed gears on the hub and your derailleur is either in or out. There is no in-between to fiddle with. Oh, and you don't have to dish the wheel. Drive and non-drive spokes carry an equal load. Yea, I'm selling it. I know. But I think it's a good system. I originally added a front derailleur to this system to get 12 speeds, but I would get lost trying to figure out how to shift next.

Three on the hub and two cogs is simple and effective for a lot of riding situations.

I would like to try out a newer Sunrace Sturmey-Archer hub. It looks like they are doing a good job with the line. I like the idea of the rotary pull cable system rather than the traditional cable pull system. And no in-between neutral.



You may have noticed that I didn't get the derailleur on here yet. I chose this picture because it shows the two cogs well.

tiger1964 

Approaching the event horizon for OT, but y'all have me pondering which brand -- if either -- is what I want for an anticipated IGH project. Sounds like a trade-off between reliability vs. difficult service, and that's before discussing friction losses and desired gearing. ​​​​​​​ ​​​​​​​

​​​​​​​...but not wanting one that also adds a derailleur and freewheel.

base2 

The Sturmey brand is better than ever now. It's the old ones made in England to dubious standards with worn out tooling that earned them a spotty reputation in later years before their bankruptcy going on 2 decades ago.

When they were bought out all the tooling was hauled to Asia where it was discovered to be junk & subsequently replaced with the best modern industry could muster.

Just mind the 1:1 drive ratio (one of the lowest available) & like all IGH hubs pause then shift. You'll be pleasantly surprised.

Do you really need lower than 20.7 gear inches with a 700x38? If not, at $200 what's not to love?

The external chain shift mechanism does work best run down the seat stay on account of heel interference/clearance issues on the chainstay when pedaling. That is easily solved with a pulley &/or the proper arrangement of cable stops along the top tube like you would find on an old school mountain bike or a few year old CX bike.

I use mine with a 31.8 Paul Components SRAM shifter pod clamp to affix the SRAM XO shifter to the handlebar & effect derailleur shifting with conventional 1x drop bar shifters.