Sturmey Archer RX-RD5 problems

[Brucey]

broken cable in situ

different shifter; same model, same problem

cheers

[Ian W]

Right, new shifter ordered to see if it makes any difference at all. If it doesn't then at least I will know where the problem lies.

I took a look at the hub and I can't see anything on the brake backplate, but there was the remnants of a number on the hub. I wiped it with my finger and the number promptly wiped off...

[Brucey]

the shifter may have helped cause some problems but it won't affect fifth gear so much; I'd lay the blame (amongst things that you can control, anyway) for that at the door of the cable condition (vs the spring preload on the shift mechanism).

Did you check the condition of the sun-locking pawls?

cheers

[Ian W]

I was just hoping to work out if the shifter was causing the problem of selecting gears 1-4 not being as smooth as they could be. You explained brilliantly what the problems with 5th may be due to.

I haven't opened the hub again, but the pawls seemed ok to my inexperienced eyes.

[Brucey]

the usual shifting technique that works best with SA hubs is to pedal forwards -but without any load- whilst shifting gears. Freewheeling or backpedalling either don't always work or can create additional problems of various kinds. There are one or two shifts on one or two models which arguably may go better with backpedalling but these are very much the exception, so if you have to choose just one technique the pedalling forwards one is favourite.

I have not ridden an RX-series hub long enough to see if there are any unusual quirks but the main difference to most other SA hubs is the rotary shift actuation. IME such arrangements are sensitive to the cable (of course) but also condition of the cams and how they are lubricated.

FWIW one of the things you shouldn't do with any SA hub is try and shift under load. There are a few shifts in a few hubs where this is OK but in the main it isn't. Note that in rotary shifting hubs if the sun locking selector drum is forced round whilst there is load through the transmission, the loaded pawls cannot move (they are jammed in position because of the applied torque) and the movement of the selector drum loads the followers (the rightward parts of each pawl piece). I have seen damaged followers in 8s hubs which use the same kind of sun locking and I think it arose in this way.

By contrast in a shimano hub there is a shift control spring that is wound up should the sun locking pawls be jammed because of the applied torque. This limits the load that can be passed through the selector mechanism and delays the shift until either there is no torque applied or a shift servo mechanism is engaged. This isn't infallible by any means but it is a bit more proof against clumsy use.

cheers

[Ian W]

After a period of time using the trigger shifter, I can honestly say it is so much better than the thumbshifter. The gear changes are more positive, less noise and crunching from the hub, and even gear 5 has remained in place occasionally. (Gear 5 still skips occasionally though.)

I continued to ensure that I wasn't putting pressure on the pedals during each change and, whilst not completely problem free, the bike is so much better.

Thanks to everyone who suggested ideas, especially Brucey!