Double Shifting?



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Richard

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I have this problem shifting my rear derallieur (did I spell it right?)

Somewhere in the middle of my 8-speed cassette it feels like the chain jumps two cogs when shifting
while on a hill. It could be the same cog involved each time. Other cogs shift just fine. It is an
intermittent but frequent problem. I don't mean straining to get up a steep hill, either- just a
down(up?)shift as pedaling gets harder. I can't adjust it out. Of course it shifts perfectly on the
work stand.

It always takes me be surprise, no matter how many times it happens on a ride so I haven't been able
to prepare and see which cog I am on before hand. This on a recumbent with a fairly long chain line.
Never used to have shifting problems.

I have a new HG-90 chain and new XT 8-30 cassette. I also replaced cables- not the first time by
far. I'm normally a fairly decent wrench. Since my stuff is a few years old could I have a problem
with cable diameter compatability with the Shimano Bar End Shifter? It it just poor adjustment? Any
suggestions will be appreciated.

Richard
 
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Sheldon Brown

Guest
Richard wrote:
> I have this problem shifting my rear derallieur (did I spell it right?)

See: http://sheldonbrown.com/derailer.html

> Somewhere in the middle of my 8-speed cassette it feels like the chain jumps two cogs when
> shifting while on a hill. It could be the same cog involved each time. Other cogs shift just fine.
> It is an intermittent but frequent problem. I don't mean straining to get up a steep hill, either-
> just a down(up?)shift as pedaling gets harder. I can't adjust it out. Of course it shifts
> perfectly on the work stand.
>
> It always takes me be surprise, no matter how many times it happens on a ride so I haven't been
> able to prepare and see which cog I am on before hand. This on a recumbent with a fairly long
> chain line. Never used to have shifting problems.
>
> I have a new HG-90 chain and new XT 8-30 cassette. I also replaced cables- not the first time by
> far. I'm normally a fairly decent wrench. Since my stuff is a few years old could I have a problem
> with cable diameter compatability with the Shimano Bar End Shifter? It it just poor adjustment?
> Any suggestions will be appreciated.

Poor adjustment is by far the most likely explanation.

See: http://sheldonbrown.com/derailer-adjustment.html

Sheldon "Adjusting Barrel" Brown +----------------------------------------------+
| Check out my wife's tale of her experience |
| in the 1975 Paris-Brest-Paris at: |
| http://harrietfell.com/PBP1975.html |
+----------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone
617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
 
D

David Kunz

Guest
Richard wrote:
> I have this problem shifting my rear derallieur (did I spell it right?)
>
> Somewhere in the middle of my 8-speed cassette it feels like the chain jumps two cogs when
> shifting while on a hill. It could be the same cog involved each time. Other cogs shift just fine.
> It is an intermittent but frequent problem. I don't mean straining to get up a steep hill, either-
> just a down(up?)shift as pedaling gets harder. I can't adjust it out. Of course it shifts
> perfectly on the work stand.
>
> It always takes me be surprise, no matter how many times it happens on a ride so I haven't been
> able to prepare and see which cog I am on before hand. This on a recumbent with a fairly long
> chain line. Never used to have shifting problems.
>
> I have a new HG-90 chain and new XT 8-30 cassette. I also replaced cables- not the first time by
> far. I'm normally a fairly decent wrench. Since my stuff is a few years old could I have a problem
> with cable diameter compatability with the Shimano Bar End Shifter? It it just poor adjustment?
> Any suggestions will be appreciated.
>
> Richard

If could be a simple barrel adjustment (cable tension -- sounds like it might be tight). I'd try
Sheldon't site (as he suggested).

If after messing with the adjustments... if that doesn't fix it, and if it happens only when going
to a smaller gear (harder pedaling), and only happens some of the time, then I'd suspect that the
cable's gunked-up and not moving freely. Did you replace the housing when you replaced the cable?

It could also be a bent deraileur hanger -- but then it'd mess-up going in both directions (up and
down) and every time that you go through the gears. Did you hit your DR on something?

David
 
M

Mark Hickey

Guest
[email protected] (Richard) wrote:

>I have this problem shifting my rear derallieur (did I spell it right?)
>
>Somewhere in the middle of my 8-speed cassette it feels like the chain jumps two cogs when shifting
>while on a hill. It could be the same cog involved each time. Other cogs shift just fine. It is an
>intermittent but frequent problem. I don't mean straining to get up a steep hill, either- just a
>down(up?)shift as pedaling gets harder. I can't adjust it out. Of course it shifts perfectly on the
>work stand.

If it's happening in the middle of the cassette, it could be a bent cog (causing a premature
pickup of the chain going one way and/or the other). Or, it could be a kinked cable somewhere in
the system.

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame
 
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