readying a use fd for install

I'm a bit of a newbie with bike maintenance and tinkering and I'm finding that I am doing more and
more swapping of front derailleurs on (mostly mountain) bikes. In order to prevent extra fiddling
with the derailleur, is there an easy way to make sure the high-low adjustment screws are "centered"
(allowing maximum adjustment) before mounting? It's always frustrating to get the derailleur on to
begin adjusting the stop only to discover there's no enough adjustment room one way or the other.

Just wondering if anybody has a quick way to deal with this. Thanks.

"BD" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

I'm a bit of a newbie with bike maintenance and tinkering and I'm finding that I am doing more and
more swapping of front derailleurs on (mostly mountain) bikes. In order to prevent extra fiddling
with the derailleur, is there an easy way to make sure the high-low adjustment screws are
"centered" (allowing maximum adjustment) before mounting? It's always frustrating to get the
derailleur on to begin adjusting the stop only to discover there's no enough adjustment room one
way or the other.

Front derailers are about the most difficult thing to set up on a bike. One mail order company
reports that they are the most returned component. You have the combined dimensions of BB, seattube,
and crank to consider, plus the mounting style and pull orientation. You also have to match the
curvature with the chainring, and, of course, the amount of pull with the (indexed) shifter.

I'm not sure exactly what you mean by "centered". If you mean both stops set to the middle of their
range, I'm not sure how that helps you set up a derailer. When I'm setting up a fd, after mounting
it (not completely tightened) I manually extend the mechanism, then jam something to hold it open
while I set the height (relative to outer chainring) and rotation. New Shimanos come with a little
plastic block to do this, but it's easy to improvise something. This allows you to at least crudely
estimate the outer stop at the same time by eyeballing the fd cage against the chainring and decide
whether the mechanism has enough reach to shift into the big ring. You can get a little more by
rotating the tail of the cage outward, but too much screws up the shifting. It's harder to eyeball
the inner shifting limit, because the cage is so far above the small ring. I think that requires
putting on a chain.

For crank & BB length compatibility info, Sheldon Brown is accumulating a very useful database:
sheldonbrown.combbsize.htmlOpen ↗

BD' may have said:

I'm a bit of a newbie with bike maintenance and tinkering and I'm finding that I am doing more and
more swapping of front derailleurs on (mostly mountain) bikes. In order to prevent extra fiddling
with the derailleur, is there an easy way to make sure the high-low adjustment screws are
"centered" (allowing maximum adjustment) before mounting? It's always frustrating to get the
derailleur on to begin adjusting the stop only to discover there's no enough adjustment room one
way or the other.

Just wondering if anybody has a quick way to deal with this. Thanks.

Max throw is achieved when you have backed off all the way on both screws. I think what you're
really seeing is the effect of crank/BB mismatch, where a crank is installed on a shaft of the wrong
length, or perhaps you may be trying to use a der for a double with a triple ring; that's generally
not going to work.

--
My email address is antispammed; pull WEEDS if replying via e-mail. Yes, I have a killfile. If I
don't respond to something, it's also possible that I'm busy.

Quoted message said:

Quoted message said:

I'm a bit of a newbie with bike maintenance and tinkering and I'm

finding

Quoted message said:

Quoted message said:

that I am doing more and more swapping of front derailleurs on (mostly mountain) bikes. In order
to prevent extra fiddling with the derailleur, is there an easy way to make sure the high-low
adjustment screws are "centered" (allowing maximum adjustment) before mounting? It's always
frustrating to get the derailleur on to begin adjusting the stop only to discover there's no
enough adjustment room

one

Quoted message said:

Quoted message said:

way or the other.

Front derailers are about the most difficult thing to set up on a bike.

One

Quoted message said:

mail order company reports that they are the most returned component. You

have

Quoted message said:

the combined dimensions of BB, seattube, and crank to consider, plus the mounting style and pull
orientation. You also have to match the curvature

with

Quoted message said:

the chainring, and, of course, the amount of pull with the (indexed)

shifter.

Quoted message said:

I'm not sure exactly what you mean by "centered". If you mean both stops

set

Quoted message said:

to the middle of their range, I'm not sure how that helps you set up a derailer. When I'm setting
up a fd, after mounting it (not completely tightened) I manually extend the mechanism, then jam
something to hold it

open

Quoted message said:

while I set the height (relative to outer chainring) and rotation. New Shimanos come with a little
plastic block to do this, but it's easy to improvise something. This allows you to at least
crudely estimate the

outer

Quoted message said:

stop at the same time by eyeballing the fd cage against the chainring and decide whether the
mechanism has enough reach to shift into the big ring.

You

Quoted message said:

can get a little more by rotating the tail of the cage outward, but too

much

Quoted message said:

screws up the shifting. It's harder to eyeball the inner shifting limit, because the cage is so
far above the small ring. I think that requires

putting

Quoted message said:

on a chain.

For crank & BB length compatibility info, Sheldon Brown is accumulating a

very

Quoted message said:

useful database: sheldonbrown.combbsize.htmlOpen ↗

You hit the nail on the head (both stops set to the middle of their range). Granted, my
experience is limited, but what I've been able to do so far and with a pretty high degree of
success is to set the screws to what appears to be the middle of the range and then mount the
derailleur as you indicated. I use a block of scrap wood to hold the fd open and temporarily
tighten it down to where the outside of the cage is just above the largest chainring. At this
point, of course, all I'm looking for is approximate reach to see if the derailleur in question
has enough travel to do the job.

From what I've picked up, my dinking with the screws is really pretty irrelevant, but just makes me
feel better about the whole process : )

Thanks for the input.

Werehatrack said:

screws. I think what you're really seeing is the effect of crank/BB mismatch, where a crank is
installed on a shaft of the wrong length,

Drat! That's what happened last year with my new crankset; I knew it shouldn't need a new front
derailleur!

Oh well. It works now, I won't fsck with it.

--
Rick Onanian