Strange shifting problem

[Josh Hassol]

I recently re-cabled my rear derailleur. I adjusted the indexing and
got it working perfectly on the work stand. But when I'm out riding,
the derailleur will, from time to time, spontaneously shift to the next
smaller cog. This is not a case of BB flex causing ghost shifting. It
occurs under normal, easy pedaling, and I'm riding one of those older
Cannondale frames with the huge down tube (very stiff).

Each time the problem has occurred, I've stopped and tightened the
cable tension a little bit with the adjuster at the derailleur. It
seems to help each time but then, an hour or a day later, the same
thing happens. The chain is not "stretched," and I'm running all
Shimano stuff: Dura Ace shifters, Dura Ace chain, Ultegra cassette, 600
cranks, 105 short-cage derailleur. Nothing is worn, and it's all
clean and lubed. I've never had this problem before, despite having
re-cabled the bike a few times.

Ideas, suggestions?

 

[JeffWills]

Josh Hassol wrote:
> I recently re-cabled my rear derailleur. I adjusted the indexing and
> got it working perfectly on the work stand. But when I'm out riding,
> the derailleur will, from time to time, spontaneously shift to the next
> smaller cog. This is not a case of BB flex causing ghost shifting. It
> occurs under normal, easy pedaling, and I'm riding one of those older
> Cannondale frames with the huge down tube (very stiff).
>
> Each time the problem has occurred, I've stopped and tightened the
> cable tension a little bit with the adjuster at the derailleur. It
> seems to help each time but then, an hour or a day later, the same
> thing happens. The chain is not "stretched," and I'm running all
> Shimano stuff: Dura Ace shifters, Dura Ace chain, Ultegra cassette, 600
> cranks, 105 short-cage derailleur. Nothing is worn, and it's all
> clean and lubed. I've never had this problem before, despite having
> re-cabled the bike a few times.
>
> Ideas, suggestions?

First, the obvious: is the pinch bolt tight enough? It sounds like the
cable is being pulled out of place very slowly. Also, if you're using a
coated cable, did you remove the coating under the pinch bolt?

Then the non-obvious: how long has it been since you inspected the
housing? If one of the housing ferrules has failed, it could "shorten"
the housing by letting the wires poke through. If the housing is more
than a year or two old, replacing it would be a good idea.

Jeff

 

[dvt]

JeffWills wrote:
> Josh Hassol wrote:
>> I recently re-cabled my rear derailleur. I adjusted the indexing and
>> got it working perfectly on the work stand. But when I'm out riding,
>> the derailleur will, from time to time, spontaneously shift to the next
>> smaller cog. This is not a case of BB flex causing ghost shifting. It
>> occurs under normal, easy pedaling, and I'm riding one of those older
>> Cannondale frames with the huge down tube (very stiff).
>>
>> Each time the problem has occurred, I've stopped and tightened the
>> cable tension a little bit with the adjuster at the derailleur. It
>> seems to help each time but then, an hour or a day later, the same
>> thing happens. The chain is not "stretched," and I'm running all
>> Shimano stuff: Dura Ace shifters, Dura Ace chain, Ultegra cassette, 600
>> cranks, 105 short-cage derailleur. Nothing is worn, and it's all
>> clean and lubed. I've never had this problem before, despite having
>> re-cabled the bike a few times.
>>
>> Ideas, suggestions?
>
> First, the obvious: is the pinch bolt tight enough? It sounds like the
> cable is being pulled out of place very slowly. Also, if you're using a
> coated cable, did you remove the coating under the pinch bolt?
>
> Then the non-obvious: how long has it been since you inspected the
> housing? If one of the housing ferrules has failed, it could "shorten"
> the housing by letting the wires poke through. If the housing is more
> than a year or two old, replacing it would be a good idea.
>
> Jeff

Good suggestions. Also check the routing of the cable on the derailer;
if you run the cable on the wrong side of the pinch bolt, you won't be
able to get it adjusted correctly.

--
Dave
dvt at psu dot edu

 

[Josh Hassol]

JeffWills wrote:
>
> First, the obvious: is the pinch bolt tight enough? It sounds like the
> cable is being pulled out of place very slowly. Also, if you're using a
> coated cable, did you remove the coating under the pinch bolt?
>
> Then the non-obvious: how long has it been since you inspected the
> housing? If one of the housing ferrules has failed, it could "shorten"
> the housing by letting the wires poke through. If the housing is more
> than a year or two old, replacing it would be a good idea.
>
> Jeff

Thanks for the ideas. It sure seemed like the pinch bolt to me, too,
but I've checked it and it is tight. The cable housings are new (I
replaced them at the same time as the inner wire), and the ferrules all
look fine. It's not coated wire, just plain old Shimano stuff.

 

[Josh Hassol]

dvt wrote:
> Good suggestions. Also check the routing of the cable on the derailer;
> if you run the cable on the wrong side of the pinch bolt, you won't be
> able to get it adjusted correctly.
>
> --
> Dave
> dvt at psu dot edu

thanks. I routed it straight. I'm thinking this might just be a case
where a new cable and new housings take a few rides to stretch and get
fully seated.

 

[Kenny]

Josh Hassol wrote:
> I recently re-cabled my rear derailleur. I adjusted the indexing and
> got it working perfectly on the work stand. But when I'm out riding,
> the derailleur will, from time to time, spontaneously shift to the next
> smaller cog. This is not a case of BB flex causing ghost shifting. It
> occurs under normal, easy pedaling, and I'm riding one of those older
> Cannondale frames with the huge down tube (very stiff).

> Ideas, suggestions?

On my C'dale I had a similiar problem. What worked for me was to use a
2mm washer. I placed it between the dropout and cassette. Problem
solved.

 

[Alex Rodriguez]

In article <[email protected]>,
[email protected] says...

>Ideas, suggestions?

Clean and lube the BB guide. That's where I would look first.
--------------
Alex

 

[landotter]

How did you adjust the indexing? By eye or by feel? I don't have a work
stand at home so just flip the bike over shifted to a middle cog, and
press the jockey wheel down, making sure that it's absolutely,
positively aligned over the sprocket..

 

[Josh Hassol]

Alex Rodriguez wrote:
> In article <[email protected]>,
> [email protected] says...
>
> >Ideas, suggestions?
>
> Clean and lube the BB guide. That's where I would look first.
> --------------
> Alex

Thanks for the suggestion. I did clean the BB guide and lubed it with
tri-flow. So it's not that, I don't think.

 

[Josh Hassol]

landotter wrote:
> How did you adjust the indexing? By eye or by feel? I don't have a work
> stand at home so just flip the bike over shifted to a middle cog, and
> press the jockey wheel down, making sure that it's absolutely,
> positively aligned over the sprocket..

That's an interesting technique. I've never tried that. I'll check it
before my commute home today.

I always follow the procedure outlined in the instructions from
Shimano, or from the Park Tool website, both which, I guess, could be
classified as "by feel."

 

[daveornee]

dvt wrote:
> Good suggestions. Also check the routing of the cable on the derailer;
> if you run the cable on the wrong side of the pinch bolt, you won't be
> able to get it adjusted correctly.
>
> --
> Dave
> dvt at psu dot edu

thanks. I routed it straight. I'm thinking this might just be a case
where a new cable and new housings take a few rides to stretch and get
fully seated.

I think you are on to something here. Sometimes, the cable ends and ferrules are coming together (seating) and effectively shortening the housing.
If you want to force the process you can. Metal ferrules seen to work best for me with true Shimano SIS housing sections. I like to get the "factory" pieces for both shifter and derailer ends.

 

[Josh Hassol]

JeffWills wrote:

.. . . If one of the housing ferrules has failed, it could "shorten"
> the housing by letting the wires poke through. If the housing is more
> than a year or two old, replacing it would be a good idea.
>
> Jeff

Jeff gets the prize! In my original reply, I said that I had checked
the ferrules. But on my ride home last night, when the shifting
problem appeared yet again, I thought, "hell, let me check them again."
Sure enough the housing is not properly seated in the ferrule at the
downtube stop. Instead, the end of the housing is caught on the edge
of the ferrule. It must have done that as I was pulling the cable
through. As a result, some of the housing wires are coming out, and
squeezing down along the outside of the ferrule. This causes the cable
tension to diminish over time.

Easy to fix (tonight), but I never would have checked again if Jeff
hadn't planted that seed in my mind. Thanks!

 

[Lou Holtman]

Josh Hassol wrote:
> JeffWills wrote:
>
> . . . If one of the housing ferrules has failed, it could "shorten"
>
>>the housing by letting the wires poke through. If the housing is more
>>than a year or two old, replacing it would be a good idea.
>>
>>Jeff
>
>
> Jeff gets the prize! In my original reply, I said that I had checked
> the ferrules. But on my ride home last night, when the shifting
> problem appeared yet again, I thought, "hell, let me check them again."
> Sure enough the housing is not properly seated in the ferrule at the
> downtube stop. Instead, the end of the housing is caught on the edge
> of the ferrule. It must have done that as I was pulling the cable
> through. As a result, some of the housing wires are coming out, and
> squeezing down along the outside of the ferrule. This causes the cable
> tension to diminish over time.
>
> Easy to fix (tonight), but I never would have checked again if Jeff
> hadn't planted that seed in my mind. Thanks!
>


Good feedback. Thanks.

Lou
--
Posted by news://news.nb.nu

 

[JeffWills]

Josh Hassol wrote:
> JeffWills wrote:
>
> . . . If one of the housing ferrules has failed, it could "shorten"
> > the housing by letting the wires poke through. If the housing is more
> > than a year or two old, replacing it would be a good idea.
> >
> > Jeff
>
> Jeff gets the prize! In my original reply, I said that I had checked
> the ferrules. But on my ride home last night, when the shifting
> problem appeared yet again, I thought, "hell, let me check them again."

Vindication! I will do the magic cone dance tonight!
http://photostore.chrisleck.com/gallery/620182/4

Jeff