Wednesday, December 17, 2014

Sturmey Archer Hub Gear Ratio Notes

One of the nice things about Sturmey Archer AW hubs with the 3-spline cog is that you can change your gear ratio as needed.

For Sturmey Archer AW sizing in a 26 inch wheel I like:

[Front] - [Back]

(Note if you are running a conversion cog and inch pitch gearing, divide these numbers of teeth in half)

Very Hilly Terrain:

2-1 (46-23), (48-24)- this ratio is the max low that Sturmey Archer suggested back in the day for the AW hub. They suggested not going lower because they believed it exerted too much force on the hub internals. I've not tested this theory, but 2-1 is pretty low. N is mostly a climbing gear but not bad on a flat into the wind. I suppose you could go lower, but I don't press it with older hubs and I stick to the old Sturmey Archer advice. Perhaps the modern hubs will tolerate it, but I haven't messed around with new hubs much.

Moderately Hilly: 

46-22, 48-23- works reasonably well. Goes OK on a flat. Can climb in L, or smaller hills in N. Has slightly more top end than 2-1 but not much.

Somewhat hilly, or if you like a lower gear a little below stock: 

46-20, 46-21, 48-22, 48-21- Climb mostly in L, N is peppy enough to run well on a flat or into a breeze. I like this ratio for all-around riding. It's a little slower than stock, but I like how it lets you "spin" a little more and is easier on the knees than stock.

Flat:

46-18, 48-18 (18 is stock), 48-20- I think Sturmey Archer set the stock gear ratio too high on these hubs. 18 strikes me as not making the most of that low gear for climbing. On a flat, stock goes well (or 20 on a 48 tooth sprocket), but your climbing is somewhat limited and you may need low gear for going into the wind. I don't run any of my AWs with an 18 tooth cog anymore.

Top end boost:

46-16, 48-16 (this is if you want a really high gear and a lot of top end speed) I fooled with this briefly but didn't like it. It's fast but you had better live in a very flat area.

FW and SW Notes:


The rule I follow for the FW-  the gear ratio when converting between AW and FW is that the FW should be 1 tooth on the rear cog higher (smaller cog) than for the AW. The reason for this is that the FW has a lower high gear than the AW does, while providing a bottom gear. The second gear "L" is slightly higher than the AW's L but the AW doesn't have Bottom. That said, if you want max climbing, go 2-1 on the FW and you'll have better climbing than the AW. I run my Raleigh 4-speed (1958) sports 2-1 because I wanted a "climber" alternative to my standard 3-speed sports (1974). The FW is a lot of fun as well and a nice alternative if you want bottom gear.

For the SW, I don't like changing the ratio substantially because the hubs tend to cam-out more if you put a big cog on the rear, at least in my experience. I also suggest swapping out the SW on any bike you're going to ride substantially, or be climbing with. The AW is the way to go over the SW.
 
For Sturmey Archer sizing I like:
[Front] - [Back]
Very Hilly Terrain:
2-1 (46-23), (48-24)- this ratio is the max low that Sturmey Archer suggested back in the day for the AW hub. They suggested not going lower because they believed it exerted too much force on the hub internals. I've not tested this theory, but 2-1 is pretty low. N is mostly a climbing gear but not bad on a flat into the wind.

Moderately Hilly: works reasonably well. Goes OK on a flat. Can climb in L, or smaller hills in N.
46-22, 48-23

Somewhat hilly, or if you like a lower gear: Climb mostly in L, N is peppy.
46-20, 46-21, 48-22, 48-21

Flat:
46-18, 48-18 (18 is stock), 48-20

Top end boost:

46-16, 48-16 (this is if you want a really high gear and a lot of top end speed)

For Sturmey Archer sizing I like:
[Front] - [Back]
Very Hilly Terrain:
2-1 (46-23), (48-24)- this ratio is the max low that Sturmey Archer suggested back in the day for the AW hub. They suggested not going lower because they believed it exerted too much force on the hub internals. I've not tested this theory, but 2-1 is pretty low. N is mostly a climbing gear but not bad on a flat into the wind.

Moderately Hilly: works reasonably well. Goes OK on a flat. Can climb in L, or smaller hills in N.
46-22, 48-23

Somewhat hilly, or if you like a lower gear: Climb mostly in L, N is peppy.
46-20, 46-21, 48-22, 48-21

Flat:
46-18, 48-18 (18 is stock), 48-20

Top end boost:

46-16, 48-16 (this is if you want a really high gear and a lot of top end speed)

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