I just meant that it's better to have the low gear be the direct drive one, if you spend lots of time going up hills.
ah, I see what you mean! I suspect this feature comes (as much as anything else) from a desire to make the hub more suitable for small-wheelers whilst retaining sensible chainring/sprocket sizes
rfryer wrote:Another thing worth noting about the SRAM Automatix (unless it's peculiar to my example) is that jolts to the hub can cause premature shifting. The hub has a hair-trigger for shifting from low to high, but shifting back down involves taking pressure off the drive....
you are quite right, all the examples I have ridden do exactly this, and as you say it is worse with skinny tyres and on bumpy roads. I've also had a Moulton with the same hub and (despite fat tyres) it was about as bad as a rigid machine with skinny tyres, presumably because the suspension allows the wheel to jiggle up and down more than it might otherwise.
The effect of this is that there is effectively a narrow range of speeds that ought to be avoided whilst in the low gear; to my mind it makes a fair bit of sense to set the shift point so that one is pedalling faster than is comfortable (for any length of time) in the low gear. This way it is less likely that the shift will come when you don't want it, and if you should want to ride at that road speed, you can still do it using the high gear. A snag with this is that the hub will downshift every time you freewheel, and this will force you to speed up again (briefly) in order to initiate the shift.
In point of fact the shift control mechanism inside the hub ought to be mass-balanced, and thus more or less immune to jolts; there are two opposed weights which are coupled via a shift control plate. However only one has a (shift control) spring on it, plus there are clearances that allow the weights to chatter, and the shift control plate will move more easily in one direction than the other, thus shifts are not as well controlled as one would like.
At some point I plan to install two (identical, but each weaker than normal) springs so that each weight has its own spring. I think this ought to make the shifting slightly less erratic. If that doesn't do enough good, I might try reworking the shift control plate so that there isn't so much clearance between this and the other parts, thus allowing less chatter.