casette shifting, again
 

Maybe you remember my problem with the smaller
sprockets being unreachable. After degreasing
and lubing the whole thing it got better, but
then the problem returned and now worse than
ever. Because of the constant rain and snow
here, I thought, OK, so it needs lube to work,
and the water washes it away. But eventually
I got tired of it and now I have a new cable
and it works great. Every single sprocket is
reachable. Maybe tomorrow it won't work again.
But let's assume it still works, so questions:

1) Does this makes sense in theory? If the
cable was shot, doesn't that mean the
bigger, not the smaller sprockets
being unreachable?

2) Except for the obvious cases when the cable
is all stiff and bent, how can one
examine/determine its quality?

3) I don't know how much this bike has been
used, but it looks very unused. The brake
discs are, at least. I've used it every day
a couple of months, for a time ~20km/day,
but more often less than that. Is this
enough to wear out a cable? How long does
a cable last?

--
underground experts united
http://user.it.uu.se/~embe8573

casette shifting, again
 

On 12/12/2018 12:16 PM, Emanuel Berg wrote:
Maybe you remember my problem with the smaller
sprockets being unreachable. After degreasing
and lubing the whole thing it got better, but
then the problem returned and now worse than
ever. Because of the constant rain and snow
here, I thought, OK, so it needs lube to work,
and the water washes it away. But eventually
I got tired of it and now I have a new cable
and it works great. Every single sprocket is
reachable. Maybe tomorrow it won't work again.
But let's assume it still works, so questions:

1) Does this makes sense in theory? If the
cable was shot, doesn't that mean the
bigger, not the smaller sprockets
being unreachable?

I think what you found makes perfect sense. It's your muscles that pull
the cable to shift to the bigger sprockets. It's only the small springs
in the derailleur that drag the cable back to allow shift to the small
sprockets. If the cable is rusted, kinked, etc. the springs will have a
hard time.

But as we may have said before, it's not necessarily the cable itself.
I've experienced shifting problems caused by friction and/or dirt where
the cable passes through a channel under the bottom bracket. Cleaning
and lubricating there fixed the problem.

Also, if housing ends are not cut square, their edges may drag on the
cable. That should be visually obvious.

2) Except for the obvious cases when the cable
is all stiff and bent, how can one
examine/determine its quality?

I suppose one could pull alternately on each end of the cable to be sure
it slides freely. Or do the same before and after the cable passes
through a section of housing.

The 180 degree housing just before the derailleur is sometimes a
problem. I had an early mountain bike that used cable housing in a U
shape to turn the front derailleur's cable from the downtube to the seat
tube. The ends of that housing faced upward, and would catch water and
cause rust or ice to form inside. The problem could be felt by tugging
the cable.


3) I don't know how much this bike has been
used, but it looks very unused. The brake
discs are, at least. I've used it every day
a couple of months, for a time ~20km/day,
but more often less than that. Is this
enough to wear out a cable? How long does
a cable last?

In my experience, cables last almost forever if they are lubricated
every few years. And lots of modern cable housing is lined and doesn't
require lubrication.

The exception is a cable that undergoes sharp bend, such as the end of a
shift cable that wraps tightly around a shift lever. I can feel when one
of those starts snapping individual strands. Then it's time for replacement.


--
- Frank Krygowski

casette shifting, again
 

On Wed, 12 Dec 2018 18:16:47 +0100,
Emanuel Berg wrote:
Maybe you remember my problem with the smaller sprockets being
unreachable. After degreasing and lubing the whole thing it got
better, but then the problem returned and now worse than ever.
Because of the constant rain and snow here, I thought, OK, so
it needs lube to work, and the water washes it away. But
eventually I got tired of it and now I have a new cable and it
works great. Every single sprocket is reachable. Maybe tomorrow
it won't work again. But let's assume it still works, so
questions:

1) Does this makes sense in theory? If the cable was shot,
doesn't that mean the bigger, not the smaller sprockets
being unreachable?

It makes complete sense to me, for the reasons Frank gave.
Recently I had the same problem, my rear derailer would not shift
to the smaller cogs without some help (i.e., pushing outward on
the derailer). Lubing the cable in the housing did not help, and
when I looked more closely I found that at least one strand of the
cable had broken and was frayed away from the cable where it
exited the rear of the front section of housing (i.e., under the
down tube).

I tried to replace the cable, but could not pass it through the
old housing--so something inside of the housing had been damaged
(or there was still a fragment of a cable strand embedded inside
it). After replacing the housing, I was able to easily pass the
new cable through it and the shifting worked well again.

--
Ted Heise West Lafayette, IN, USA

casette shifting, again
 

On Wednesday, December 12, 2018 at 9:16:50 AM UTC-8, Emanuel Berg wrote:
Maybe you remember my problem with the smaller
sprockets being unreachable. After degreasing
and lubing the whole thing it got better, but
then the problem returned and now worse than
ever. Because of the constant rain and snow
here, I thought, OK, so it needs lube to work,
and the water washes it away. But eventually
I got tired of it and now I have a new cable
and it works great. Every single sprocket is
reachable. Maybe tomorrow it won't work again.
But let's assume it still works, so questions:

1) Does this makes sense in theory? If the
cable was shot, doesn't that mean the
bigger, not the smaller sprockets
being unreachable?

2) Except for the obvious cases when the cable
is all stiff and bent, how can one
examine/determine its quality?

3) I don't know how much this bike has been
used, but it looks very unused. The brake
discs are, at least. I've used it every day
a couple of months, for a time ~20km/day,
but more often less than that. Is this
enough to wear out a cable? How long does
a cable last?

--
underground experts united
http://user.it.uu.se/~embe8573

I use stainless cables and housings now and haven't had any troubles from that reason but I see where it could if you're using steel cables and especially those "Teflon" coated cables which very rapidly peal the non-stick coating off.

A source of this problem I used to have is the joints in the rear derailleur wearing and jamming somewhat. Since the return spring is near zero pressure near the bottom is doesn't require a whole lot of additional friction to keep it from bottoming out.

casette shifting, again
 

Theodore Heise wrote:

It makes complete sense to me, for the
reasons Frank gave. Recently I had the same
problem, my rear derailer would not shift to
the smaller cogs without some help (i.e.,
pushing outward on the derailer). Lubing the
cable in the housing did not help, and when
I looked more closely I found that at least
one strand of the cable had broken and was
frayed away from the cable where it exited
the rear of the front section of housing
(i.e., under the down tube).

Yes, that makes sense in the "cable damage"
sense, but not in the "cable extension" sense,
because then the shifting problem would be the
opposite, right?

But perhaps this is what happens to the cable,
it get damaged so it interferes with the
housing? How does this damage happen BTW?

I thought the general problem was the cable
loosed its integrity or internal strength, so
it got just a bit longer, much like a bicycle
chain, but enough to mess things up?

Also, as for lubing, how is this done?
Remove the housing, pull out the cable, drip
into the housing and then pull the cable back
and forth to distribute the oil? Seems like
a lot of work! How often is this
typically done?

--
underground experts united
http://user.it.uu.se/~embe8573

casette shifting, again
 

On 12/12/2018 4:58 PM, Emanuel Berg wrote:

I thought the general problem was the cable
loosed its integrity or internal strength, so
it got just a bit longer, much like a bicycle
chain, but enough to mess things up?

The cable itself is not going to get stretched with use, if that's what
you mean. That would require forces many, many times larger than what's
being applied in normal operation.

Also, as for lubing, how is this done?
Remove the housing, pull out the cable, drip
into the housing and then pull the cable back
and forth to distribute the oil? Seems like
a lot of work! How often is this
typically done?

I find it easier to loosen the clamp screw at the derailleur or brake,
remove any cable end anti-fray gizmo, pull out the cable, wipe it down
with a light coat of oil, then thread it back through the housing and
re-clamp. Re-do any anti-fray measure. The housing can stay in place.

If the cable runs through external cable guides, be sure those too are
clean and lubricated. At the risk of sounding obsessive, paraffin wax
works pretty well as a dry lubricant on such surfaces.


--
- Frank Krygowski

casette shifting, again
 

On Wed, 12 Dec 2018 22:58:25 +0100,
Emanuel Berg wrote:
Theodore Heise wrote:

It makes complete sense to me, for the reasons Frank gave.
Recently I had the same problem, my rear derailer would not
shift to the smaller cogs without some help (i.e., pushing
outward on the derailer). Lubing the cable in the housing did
not help, and when I looked more closely I found that at least
one strand of the cable had broken and was frayed away from
the cable where it exited the rear of the front section of
housing (i.e., under the down tube).

Yes, that makes sense in the "cable damage" sense, but not in
the "cable extension" sense, because then the shifting problem
would be the opposite, right?

Not sure about this. I think it's two different failure modes,
and if the cable length changes it affects shifting across all (or
nearly all) of the cassette.


But perhaps this is what happens to the cable, it get damaged
so it interferes with the housing? How does this damage happen
BTW?

In my case it was because one of the cable strands had fractured,
and most likely the factured end (or the frayed strand) damaged
the inside surface of the housing--or became lodged in it.

--
Ted Heise West Lafayette, IN, USA

casette shifting, again
 

On Wed, 12 Dec 2018 17:15:45 -0500,
Frank Krygowski wrote:
On 12/12/2018 4:58 PM, Emanuel Berg wrote:
I thought the general problem was the cable loosed its
integrity or internal strength, so it got just a bit longer,
much like a bicycle chain, but enough to mess things up?

The cable itself is not going to get stretched with use, if
that's what you mean. That would require forces many, many
times larger than what's being applied in normal operation.

I think that's correct, and yet on my tandems I've sometimes seem
some changes in shifting that I attribute to change in cable
length--maybe more due to temperature changes than to actual
physical stretching. For example, when we go out on a very warm
day after having ridden in cold weather for a time, I often have
to tighten the adjuster just a smidge.

--
Ted Heise West Lafayette, IN, USA

casette shifting, again
 

On Wed, 12 Dec 2018 22:58:25 +0100, Emanuel Berg
wrote:

Theodore Heise wrote:

It makes complete sense to me, for the
reasons Frank gave. Recently I had the same
problem, my rear derailer would not shift to
the smaller cogs without some help (i.e.,
pushing outward on the derailer). Lubing the
cable in the housing did not help, and when
I looked more closely I found that at least
one strand of the cable had broken and was
frayed away from the cable where it exited
the rear of the front section of housing
(i.e., under the down tube).

Yes, that makes sense in the "cable damage"
sense, but not in the "cable extension" sense,
because then the shifting problem would be the
opposite, right?

But perhaps this is what happens to the cable,
it get damaged so it interferes with the
housing? How does this damage happen BTW?

I thought the general problem was the cable
loosed its integrity or internal strength, so
it got just a bit longer, much like a bicycle
chain, but enough to mess things up?

Also, as for lubing, how is this done?
Remove the housing, pull out the cable, drip
into the housing and then pull the cable back
and forth to distribute the oil? Seems like
a lot of work! How often is this
typically done?

Or you can buy cable that is plastic coated and never needs oiling :-)

cheers,

John B.

casette shifting, again
 

On 12/12/2018 5:29 PM, Theodore Heise wrote:
On Wed, 12 Dec 2018 17:15:45 -0500,
Frank Krygowski wrote:
On 12/12/2018 4:58 PM, Emanuel Berg wrote:
I thought the general problem was the cable loosed its
integrity or internal strength, so it got just a bit longer,
much like a bicycle chain, but enough to mess things up?

The cable itself is not going to get stretched with use, if
that's what you mean. That would require forces many, many
times larger than what's being applied in normal operation.

I think that's correct, and yet on my tandems I've sometimes seem
some changes in shifting that I attribute to change in cable
length--maybe more due to temperature changes than to actual
physical stretching. For example, when we go out on a very warm
day after having ridden in cold weather for a time, I often have
to tighten the adjuster just a smidge.

I think apparent increases in cable length are probably due to shifting
of position of the cable inside the housing, or wear of the housing
where the cable follows it through curves, or the end of the housing
settling further into a housing stop. Maybe the temperature change
triggers something like that?

As I've mentioned, my most frequent index shifting adjustment happens
with my folding bike, especially if its sat folded for a while. I've
learned it's easiest to just change the levers to friction mode for a
while, then re-try the index mode. Somehow, most of the misadjustment
corrects itself - I guess by the cables settling into their old
equilibrium position.

I'm pretty sure that if it were feasible to run the shift cable through
a straight, rigid tube all the way from shifter to derailleur, I'd never
see that problem.


--
- Frank Krygowski