Chain rub and usable gears

In article ,
"Barry" wrote:

Do you need a triple?

I don't need a triple anymore, but this is my first bike and that's what it
came with. If/when I get a new bike, I won't get a triple. I do want a
pretty low gear, as I sometimes do very steep (though short) hills, but I
should be able to manage with a 39/27, or maybe a compact crank.

Unless your racing, the number of gears is unimportant.

I care about the number of gears only because it affects the overlap between
one chainring and the next. Overlapping gears might be seen as redundant, but
reduce the need to shift the front derailleur.

A couple of posters suggested that I should be able to get all nine sprockets
in the middle chain ring, and seven or eight (all but one or two) in the small
and big rings. I'd be happy to get six of nine without having to adjust the
cable barrel on the fly (accepting the need to trim with the shift lever).

I thank everyone for your replies, but it seems that most of these are generic
advice for front derailleurs as opposed to first-hand experience with a setup
like mine. I'd really appreciate hearing from someone who currently rides a
9-speed Shimano triple, or from a mechanic who works on this stuff.

Check the chain line. Move the front derailleur
vertically and around the seat tube. Make sure the
front derailleur has full movement inward and outward.

I run Shimano Ultegra derailleurs and 9 gear cluster.
(the cranks and chain rings are TA)

I think a triple chain ring configuration should be full utilized:
* small small chain ring
* closely spaced gear cluster

That is why I run 48,38,24 / 13,14,15,16,17,18,19,21,23.

The chain line is cheated inward, so that the four
smallest cogwheels are unavailable to the smallest
chain wheel. All cogwheels are available to the middle
and large chain wheels; though I only use the cross
chainings for brief periods. Notice that I have actual
low gears and close gearing in the middle and large
chain rings. No hole between 17 and 19.

--
Michael Press

On 6 Mar, 14:41, "Barry" wrote:
I thank everyone for your replies, but it seems that most of these are generic
advice for front derailleurs as opposed to first-hand experience with a setup
like mine. I'd really appreciate hearing from someone who currently rides a
9-speed Shimano triple, or from a mechanic who works on this stuff.

I run a Shimano 105 triple (50-39-something) with 10 cogs. The middle
chainring can do the full range. I don't know if the big-big and
little-little chainring / cog combos rub because I don't want to put
so much lateral stress on the chain, and I almost never use the little
ring anyway.

The 105 front shifter has a trimming function that allows a small
adjustment on the fly with a single click of the lever, and I
sometimes use that in, say, a big ring / middle cassette combination
but usually it's a sign that I need to drop down to the middle ring.
Information on the trimming function is at:

http://cycle.shimano-eu.com/media/te...9830599845.pdf

or

http://tinyurl.com/22e7uw

Colin

Barry wrote:
...
I thank everyone for your replies, but it seems that most of these are generic
advice for front derailleurs as opposed to first-hand experience with a setup
like mine. I'd really appreciate hearing from someone who currently rides a
9-speed Shimano triple, or from a mechanic who works on this stuff.



Well, if you throw a question out there, you will get the answers that
you get, but I am curious about the chain angles you get at the most
inner and outer rings of your rear cassette. I was always advised to
avoid them to get the most life out of your chain and cassette. Has
your bike shop mentioned this to you? You've said that they have worked
on adjusting your derailler for you.

try getting a perspective on the setup with a string back from the
headtube. use good lighting.
gear surfaces in line reduce chain rub.
surfaces not seen on rear cogs, deray pulleys thu movement, and CR are
in line, those snot are snot inline.
imagine the ways/directions/movements, or draw that, rear hub and
CR's, deray and pulleys in cage, and front deray go out of line then
multiply cumulative effect.
rear wheel out of line 2 ways, deray pulley out of line.... the system
loooooooses significant stright chain approach: bowling alley narrows
to a gutter.
seeing that as a system in or out of line is a learned ability
acheived by doing what?
looking at it in various ways, eg stringing it, and thinking about it
analytically.
the LBS may not be up to the task or not at the time you walk in
or...what's a complete tranmission line tuneup cost at the LBS? wrok
guaranteed?
maintaining a straight chain line on 8/2 with a friction shifter prob
increases chain life 46% based on latest analyses.

a nth way of looking at your problem. Riders in competition run more
effective chainline setups than street bikes. Higher levels of
competition run higher than lower levels.
You are at the barrel's bottom. Not only do you not know if it's
running misaligned, you do not know what misaligned is nor what
correct operation is. Not in a position for checking LBS work that's
fersure.
Gotta learn to DIY.
take a look around at street MTB. Where's the average efficency elevl
there?

but I am curious about the chain angles you get at the most inner and outer
rings of your rear cassette. I was always advised to avoid them to get the
most life out of your chain and cassette.

Not quite sure what you mean. Are you suggesting always avoiding the smallest
and largest sprockets, or just avoiding the cross-chained combinations? I
never try to use the extreme combinations, and seldom use the largest
sprocket. I do sometimes use the middle chain ring with the smallest
sprocket, to avoid shifting to the big chain ring if I don't think I'll stay
there long.

Information on the trimming function is at:

Thanks for the link. I have the older 9-speed version (5500) but found the
proper service instruction on Shimano's website. I do trim in the middle and
small chainrings, but didn't think that trim was available on the large
chainring, too. I'll try to use a lighter touch and see if it works.

Barry wrote:
but I am curious about the chain angles you get at the most inner and outer
rings of your rear cassette. I was always advised to avoid them to get the
most life out of your chain and cassette.

Not quite sure what you mean. Are you suggesting always avoiding the smallest
and largest sprockets, or just avoiding the cross-chained combinations? I
never try to use the extreme combinations, and seldom use the largest
sprocket. I do sometimes use the middle chain ring with the smallest
sprocket, to avoid shifting to the big chain ring if I don't think I'll stay
there long.



I was referring to avoiding the cross chained combinations. Just
thought I would mention it, but glad you have a handle on this already.

In article
,
datakoll wrote:

try getting a perspective on the setup with a string back from the
headtube. use good lighting.
gear surfaces in line reduce chain rub.
surfaces not seen on rear cogs, deray pulleys thu movement, and CR are
in line, those snot are snot inline.
imagine the ways/directions/movements, or draw that, rear hub and
CR's, deray and pulleys in cage, and front deray go out of line then
multiply cumulative effect.
rear wheel out of line 2 ways, deray pulley out of line.... the system
loooooooses significant stright chain approach: bowling alley narrows
to a gutter.
seeing that as a system in or out of line is a learned ability
acheived by doing what?
looking at it in various ways, eg stringing it, and thinking about it
analytically.
the LBS may not be up to the task or not at the time you walk in
or...what's a complete tranmission line tuneup cost at the LBS? wrok
guaranteed?
maintaining a straight chain line on 8/2 with a friction shifter prob
increases chain life 46% based on latest analyses.

Is that one of the 87% of made up statistics?

--
Michael Press