Unwanted upshifting from 4th to fifth cog

On 5/1/10 4:12 PM, Mike Jacoubowsky wrote:
"bcdrums" wrote in message
...
On 5/1/10 3:06 PM, Mike Elliott wrote:
bcdrums wrote:
I have a typical 9 speed triple road setup, all Shimano except for a
SRAM chain. I have bar-end shifters, not brifters. Lately, after I
shift from cog 3 to 4, moments later the chain will drop to 5.

I adjusted the cable length on the derailler to make the cable longer,
but that did not help. I checked the chain for elongation, but it is
only about 1/32" long. I looked at the cogs for a clue, but they don't
appear to be very worn, or perhaps I am not seeing it.
About a month ago I changed the cables and housings for the brakes and
shifters, but the problem is more recent.

Any suggestions as to what might be causing this?

The first thing I check when shifting gets dodgy is the cable tension. I
shift to the smallest rear cog and check the shifter cable (the cable,
not the housing) to see if there's any slack. If so, I loosen the cable
clamp on the rear der and tug the looseness out of the cable.*

This might not work for you, of course, because you might have something
else going on, but it's generally my go-to procedure.

==========
* There are barrel tensioner-like thingies on where the der cables exit
the shifters but those have never done anything useful, near as I can
tell -- I'm not even certain what they are there for.


Mike,

I did check the cable tension at your suggestion. It seems okay- it
shifts up and down correctly across all cogs while on the stand (of
course it does!).

In case you are not just putting my leg on about the barrel adjuster,
I will send you to Sheldon for his explanation of its purpose.

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

As it turns out, Sheldon also has an article on spontaneous
upshifting- which is my problem. I read it, and he said that the most
frequent cause is a sticky cable at the bottom bracket, exacerbated by
a strong heavy rider (which I am not). I will check this out too.

BC
Sheldon fan

Cytomax dripping down a shift cable has been the cause of many shifting
issues. Funny that you can get better shifting by using a bottle that
seals better. :-)

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA

Leak proof bottle? sounds like a business opportunity.

I have just now cleaned & re-lubed the cable guides under the bottom
bracket. The guides are cut into the shell with a little bridge brazed
over the channel so the cable cannot wander off.

BC
misguided

bcdrums wrote:
I have a typical 9 speed triple road setup, all Shimano except for a
SRAM chain. I have bar-end shifters, not brifters. Lately, after I shift
from cog 3 to 4, moments later the chain will drop to 5.

I adjusted the cable length on the derailler to make the cable longer,
but that did not help. I checked the chain for elongation, but it is
only about 1/32" long. I looked at the cogs for a clue, but they don't
appear to be very worn, or perhaps I am not seeing it.
About a month ago I changed the cables and housings for the brakes and
shifters, but the problem is more recent.

Any suggestions as to what might be causing this?

Check for kinks or frays in the gear wire, inspect for
damaged casing, replace as needed. If you see any plastic
ferrules, replace with metal ones. Ensure casing runs are
smooth and unimpeded through the full motion of the handlebar.

Look for cable adjusters which are cracked or adjusted
beyond thread engagement. Check the bolts in your derailleur
rollers- are they tight? Is the cassette lockring snug? Any
play in the hub or cassette bearing? Inspect for bent
changer mount, ensure changer mounting bolt is tight in
frame, inspect for bent cage or bash marks on outer side of
body.

Oil the gear wire where it passes the nylon gear plate on
the bottom of your frame.

Yours is among the most durable and dependable shifters ever
made, highly unlikely to be a shifter problem.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On 5/1/10 5:29 PM, AMuzi wrote:
bcdrums wrote:
I have a typical 9 speed triple road setup, all Shimano except for a
SRAM chain. I have bar-end shifters, not brifters. Lately, after I
shift from cog 3 to 4, moments later the chain will drop to 5.

I adjusted the cable length on the derailler to make the cable longer,
but that did not help. I checked the chain for elongation, but it is
only about 1/32" long. I looked at the cogs for a clue, but they don't
appear to be very worn, or perhaps I am not seeing it.
About a month ago I changed the cables and housings for the brakes and
shifters, but the problem is more recent.

Any suggestions as to what might be causing this?

Check for kinks or frays in the gear wire, inspect for damaged casing,
replace as needed. If you see any plastic ferrules, replace with metal
ones. Ensure casing runs are smooth and unimpeded through the full
motion of the handlebar.

Look for cable adjusters which are cracked or adjusted beyond thread
engagement. Check the bolts in your derailleur rollers- are they tight?
Is the cassette lockring snug? Any play in the hub or cassette bearing?
Inspect for bent changer mount, ensure changer mounting bolt is tight in
frame, inspect for bent cage or bash marks on outer side of body.

Oil the gear wire where it passes the nylon gear plate on the bottom of
your frame.

Yours is among the most durable and dependable shifters ever made,
highly unlikely to be a shifter problem.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Thanks for the thorough check list. I oiled the cable where it passes
beneath the bottom bracket, although I don't have a nylon plate- the
guides are cut into the shell.

If that does not solve the problem, I will take out the cable and casing
for inspection. They are recent, maybe 5 weeks since installation, but
who knows, could be kinked somewhere. I did check the derailler mount
bolt, and it is tight. The pulleys line up correctly under the
sprockets, so I don't suspect that it is bent.

Will be checking all that you suggested. Thanks again!

BC

On May 1, 11:36*am, bcdrums wrote:
I have a typical 9 speed triple road setup, all Shimano except for a
SRAM chain. I have bar-end shifters, not brifters. Lately, after I shift
from cog 3 to 4, moments later the chain will drop to 5.

I adjusted the cable length on the derailler to make the cable longer,
but that did not help. I checked the chain for elongation, but it is
only about 1/32" long. I looked at the cogs for a clue, but they don't
appear to be very worn, or perhaps I am not seeing it.
About a month ago I changed the cables and housings for the brakes and
shifters, but the problem is more recent.

Any suggestions as to what might be causing this?

BC
shifty

I had this once but in the opposite direction -- whenever downshifting
from 4th to 3rd it would skip right over and end up in 2nd with the
chain noisily unaligned. Turned out to be a bit of the 3rd sprocket
that had been hit by something and bent inward slightly.

-pm

On Sat, 01 May 2010 12:06:02 -0700, Mike Elliott
wrote:

bcdrums wrote:
I have a typical 9 speed triple road setup, all Shimano except for a
SRAM chain. I have bar-end shifters, not brifters. Lately, after I shift
from cog 3 to 4, moments later the chain will drop to 5.

I adjusted the cable length on the derailler to make the cable longer,
but that did not help. I checked the chain for elongation, but it is
only about 1/32" long. I looked at the cogs for a clue, but they don't
appear to be very worn, or perhaps I am not seeing it.
About a month ago I changed the cables and housings for the brakes and
shifters, but the problem is more recent.

Any suggestions as to what might be causing this?

The first thing I check when shifting gets dodgy is the cable tension. I
shift to the smallest rear cog and check the shifter cable (the cable,
not the housing) to see if there's any slack. If so, I loosen the cable
clamp on the rear der and tug the looseness out of the cable.*

This might not work for you, of course, because you might have something
else going on, but it's generally my go-to procedure.

Also check the cable for permanent bends or kinks. I've bent them (by
snagging on objects) and it makes the cable 'springy'.

This is followed by unreliable shifting and self-shifting. The only
cure I know of is cable replacement. I've never managed to strighten
out permanent bends in cable so it's 100% OK.

I had an unusual problem with bar-ends recently. The fixing bolt had
worked loose, so the shifters could rotate in the handlebar. I knew
it was causing poor shifting, and I would occassionally straighten
them, but it was only when I bothered to tighten them up firm and
greatly improved the shifting that I realized how much of a problem it
was.