Rear Derailleur Problems - Go Down one at a time - go up twoat a time

On 16/09/2006 12:52, PUSHERBOT said,

Shifting from smallest cog to biggest cog works fine - one cog at a
time. I'm pretty sure the tension is right or at least pretty close
here. However, when shifting from biggest cog to smallest cog, the
derailleur will only shift two cogs at a time on every 2nd click of
the changer(or at least it is when going from 8-6 and 6-4).

I'm assuming this derailleur is high-normal, in other words if you take
the cable off, the derailleur moves to the smallest gear. If this is
the case, it sounds as if the return spring isn't doing it's job
properly. Have you lubed the derailleur itself, and does it have a
smooth easy action? If it's slightly stiff, the spring will take a bit
longer to move the chain to the next smallest gear, by which time you've
decided it isn't going to change and have another go.

--
Paul Boyd
http://www.paul-boyd.co.uk/

In article
PUSHERBOT wrote:
On Sat, 16 Sep 2006 13:25:31 +0100, Paul Boyd
wrote:

On 16/09/2006 12:52, PUSHERBOT said,

Shifting from smallest cog to biggest cog works fine - one cog at a
time. I'm pretty sure the tension is right or at least pretty close
here. However, when shifting from biggest cog to smallest cog, the
derailleur will only shift two cogs at a time on every 2nd click of
the changer(or at least it is when going from 8-6 and 6-4).

I'm assuming this derailleur is high-normal, in other words if you take
the cable off, the derailleur moves to the smallest gear. If this is
the case, it sounds as if the return spring isn't doing it's job
properly. Have you lubed the derailleur itself, and does it have a
smooth easy action? If it's slightly stiff, the spring will take a bit
longer to move the chain to the next smallest gear, by which time you've
decided it isn't going to change and have another go.

Yeah -it's high normal. The odd thing is it's not slow moving as you
suggest (and which I might expect) . It will stay there all day until
I drop down a second gear, and it then jumps 2 cogs at once.

Check everything for wear and alignment. You didn't grease the cable,
did you?

PUSHERBOT wrote:
On Sat, 16 Sep 2006 13:25:31 +0100, Paul Boyd
wrote:

On 16/09/2006 12:52, PUSHERBOT said,

Shifting from smallest cog to biggest cog works fine - one cog at a
time. I'm pretty sure the tension is right or at least pretty close
here. However, when shifting from biggest cog to smallest cog, the
derailleur will only shift two cogs at a time on every 2nd click of
the changer(or at least it is when going from 8-6 and 6-4).

I'm assuming this derailleur is high-normal, in other words if you take
the cable off, the derailleur moves to the smallest gear. If this is
the case, it sounds as if the return spring isn't doing it's job
properly. Have you lubed the derailleur itself, and does it have a
smooth easy action? If it's slightly stiff, the spring will take a bit
longer to move the chain to the next smallest gear, by which time you've
decided it isn't going to change and have another go.

Yeah -it's high normal. The odd thing is it's not slow moving as you
suggest (and which I might expect) . It will stay there all day until
I drop down a second gear, and it then jumps 2 cogs at once.

From your description I think the ratchet dogs in the shifter (control
on the handlebar) are gummed up. I don't know what sort of a shifter
you have, but a test would be to detach the cable from the derailleur,
put a constant pull on the end of the cable, and click up and down on
the shifter. If you're still getting the cable coming out two stops at
a time, try overhauling, thorougly cleaning, and sparingly
relubricating the shifter.