When to replace jockeys?

S o r n i said:

Jockey WHEELS I mean!

My old XTR derailleur still works fine, but my friends
were giving me the business over my well-worn jockey
wheels. (The teeth ARE pretty rounded!)

What happens if I just keep using 'em? Can't really tell
if they're skipping or anything, but there must be a
reason why they're teethed and not just smooth. (Probably
even have and old XT or something I can cannibalize; any
set number of teeth for 9-speed?)

When they look really bad or you get problems ;-)

Really old derailleurs had jockey wheels with no teeth.

S o r n i said:

Jockey WHEELS I mean!

My old XTR derailleur still works fine, but my friends
were giving me the business over my well-worn jockey
wheels. (The teeth ARE pretty rounded!)

I remember Bulls-eye advertisements claiming that if you
used their pulleys you could save x amount of time over a
given distance.

S o r n i said:

Jockey WHEELS I mean!

My old XTR derailleur still works fine, but my friends were
giving me the business over my well-worn jockey wheels.
(The teeth ARE pretty rounded!)

What happens if I just keep using 'em? Can't really tell if
they're skipping or anything, but there must be a reason
why they're teethed and not just smooth. (Probably even
have and old XT or something I can cannibalize; any set
number of teeth for 9-speed?)

TIA,

Bill "whole mtb (Titus Switchblade) getting a bit tired,
especially now that I'm roadie scum" S.

Dear Bill,

The teeth help to drag the chain from side to side. If
they're broken off, rounded off, or reduced to wicked-
looking but impotent spikes, the rear shifting will suffer
because the derailleur cage moves in and out, but the chain
slops back and forth against the cage, twisting and
dragging and getting cocked between what's left of the
teeth and the cage.

Smooth pulleys were once used and worked, but not nearly as
well as geared pulleys.

You can compare toothed versus toothless shifting. Front
shifters have no pulley gears to guide the chain back and
forth, just a metal frame. They're much more likely to drop
chains, to under or over shift, to take longer to shift, and
to require trimming and fussing. That's one reason why so
many pictures of pros reveal a front friction lever for the
front and an index shifter for the rear.

Carl Fogel

You are correct Bullseye did claim that their pulleys were
more efficient. That was because instead of a sleeve bearing
they had roller bearings. I used to ride with Mr. Bullseye,
a very nice man, but 35 years have erased his name from my
recall banks. He also invented a platform pedal and a cam
crank sprocket. At that time we were all riding with the San
Fernando Valley , CA bike club. javaloop

S o r n i said:

Jockey WHEELS I mean!

My old XTR derailleur still works fine, but my friends
were giving me the business over my well-worn jockey
wheels. (The teeth ARE pretty rounded!)

What happens if I just keep using 'em? Can't really tell
if they're skipping or anything, but there must be a
reason why they're teethed and not just smooth. (Probably
even have and old XT or something I can cannibalize; any
set number of teeth for 9-speed?)

There's no magic in rollers or their teeth. Hell, my
favorite derailleur came with round pulleys and still shifts
well these many years later. Rollers do wear, though, and
will give a less responsive shift when they flop side to
side ( as opposed to sliding from side to side as a Centeron
or such does). Lube occasionally with anything - it is not
critical - and change them when you feel the shift is less
responsive or when one cracks.

PS-when I say "no magic", you'd be surprised how many people
believe they cause chain skip - in deep denial about their
worn chain/sprockets and really wanting the (cheaper)
rollers to be at fault.
--
Andrew Muzi www.yellowjersey.org Open every day since 1
April, 1971

Quoted message said:

You are correct Bullseye did claim that their pulleys were
more efficient. That was because instead of a sleeve
bearing they had roller bearings. I used to ride with Mr.
Bullseye, a very nice man, but 35 years have erased his
name from my recall banks. He also invented a platform
pedal and a cam crank sprocket. At that time we were all
riding with the San Fernando Valley , CA bike club.

Roger Durham, who at one time rode in boots without toeclps.

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

Quoted message said:

You can compare toothed versus toothless shifting. Front
shifters have no pulley gears to guide the chain back and
forth, just a metal frame. They're much more likely to
drop chains, to under or over shift, to take longer to
shift, and to require trimming and fussing.

I don't think your comparison is fair. The front derailer
has to shift the portion of the chain that's under a lot of
tension, while the rear derailer gets the relatively easy
job of shifting chain that is under very little tension.
Teeth or no teeth, the front derailler has a much tougher
row to hoe.

--
Dave dvt at psu dot edu

dvt said:

I don't think your comparison is fair. The front derailer
has to shift the portion of the chain that's under a lot of
tension, while the rear derailer gets the relatively easy
job of shifting chain that is under very little tension.
Teeth or no teeth, the front derailler has a much tougher
row to hoe.

Also, the front derailer must shift the chain over a much
bigger distance between gears; I've never seen a rear jump
of more than 4 teeth, but in front it's common to have a 14
tooth difference from one gear to the next (39-53).
--
Rick Onanian

On Wed, 19 May 2004 17:27:08 -0400, Rick Onanian <[email hidden]>

Quoted message said:

dvt said:

I don't think your comparison is fair. The front derailer
has to shift the portion of the chain that's under a lot
of tension, while the rear derailer gets the relatively
easy job of shifting chain that is under very little
tension. Teeth or no teeth, the front derailler has a much
tougher row to hoe.

Also, the front derailer must shift the chain over a much
bigger distance between gears; I've never seen a rear jump
of more than 4 teeth, but in front it's common to have a 14
tooth difference from one gear to the next (39-53).

Dear Rick,

While the poor front derailleur does indeed lead a harder
life in several ways than the rear, I think that
mechanically it's just rectangular cage crashing into side
of the chain until it knocks the chain off one gear, in
hopes that it will crash-land or climb up onto the other.

In contrast, a rear derailleur's toothed pulley seems to do
a much smoother job, with the chain staying centered on the
free-spinning jockey pulley's teeth instead of banging
against the sides of the cage. The pulley inside a cage
reduces under-shoot and over-shoot much better than a cage
with no pulley inside.

The front derailleur is good enough for what it does,
comparatively rare shifts befween two or three big gears,
but it's more prone to catastrophe and seems to benefit from
the easily wiggled friction shifter, as opposed to the
routinely indexed rear cluster.

Since the front is good enough, we're happy with it, which
is lucky. I doubt that there's any practical way to rig a
geared pulley on the much larger front gears.

As for the distances involved, I'm not sure if the front is
worse than the rear.

The rear will shift darned smoothly from 11 to 28 teeth,
more than doubling the number of teeth, while 39 to 53
increases only about a third. (A rough measurement of my
39/53 x 11/28 7-cog shows both chain circles expanding about
an inch and a quarter.)

Left-right, the front derailleur moves only about 3/8ths of
an inch from high to low, while the rear moves about three
times as far.

Of course, these may not be the dimensions that matter, and
the rear derailleur works on the slacker side of the chain.
The rattletrap front is the best practical derailleur, which
may be why those internal hub gizmos are beginning to make
slight inroads.

Carl Fogel

Quoted message said:

The front derailleur is good enough for what it does,
comparatively rare shifts befween two or three big gears,
but it's more prone to catastrophe and seems to benefit
from the easily wiggled friction shifter, as opposed to the
routinely indexed rear cluster.

This reminds me...when is Shimano going to offer trim in
BOTH directions? I do okay, but trimming down would be nice.

I wonder when somebody is going to invent friction brifters.
It can't be that difficult; I can imagine mechanisms for it
myself; such mechanisms exist in a million other devices.

Quoted message said:

The rear will shift darned smoothly from 11 to 28 teeth,
more than doubling the number of teeth, while 39 to 53
increases only about a third. (A rough measurement of my
39/53 x 11/28 7-cog shows both chain circles expanding
about an inch and a quarter.)

Both circle expand 1 1/4", but the front does it in a single
jump. The rear does it in 7 small steps.

The rear will shift from an 11 to 13, or from a 30 to a 34.
I doubt it would work if you put the 11 directly next to the
28. I suppose a derailer might be designed based on standard
rear derailers that moves at a much steeper angle, but we're
talking about existing equipment here.

However, if you want to talk about total range, how about
the 22-??-48 crank I have on my mtb? Or the 30-42-52 on my
road bike...
--
Rick Onanian

On Wed, 19 May 2004 18:34:30 -0400, Rick Onanian <[email hidden]>

Quoted message said:

Quoted message said:

The front derailleur is good enough for what it does,
comparatively rare shifts befween two or three big gears,
but it's more prone to catastrophe and seems to benefit
from the easily wiggled friction shifter, as opposed to
the routinely indexed rear cluster.

This reminds me...when is Shimano going to offer trim
in BOTH directions? I do okay, but trimming down
would be nice.

I wonder when somebody is going to invent friction
brifters. It can't be that difficult; I can imagine
mechanisms for it myself; such mechanisms exist in a
million other devices.

Quoted message said:

The rear will shift darned smoothly from 11 to 28 teeth,
more than doubling the number of teeth, while 39 to 53
increases only about a third. (A rough measurement of my
39/53 x 11/28 7-cog shows both chain circles expanding
about an inch and a quarter.)

Both circle expand 1 1/4", but the front does it in a
single jump. The rear does it in 7 small steps.

The rear will shift from an 11 to 13, or from a 30 to a 34.
I doubt it would work if you put the 11 directly next to
the 28. I suppose a derailer might be designed based on
standard rear derailers that moves at a much steeper angle,
but we're talking about existing equipment here.

However, if you want to talk about total range, how about
the 22-??-48 crank I have on my mtb? Or the 30-42-52 on my
road bike...

Dear Rick,

You may be right about the small steps.

I'm thinking of a spot where I turn around on at the top
of a long hill and yank the rear-gear friction lever from
low to high--

Er, I mean, a spot where I shift rapidly but smoothly from
low to high gear and by no means abuse my transmission.

(Bad habits die hard.Trials machines are equipped with
clutches, but in competition it's common to shift without
disturbing the clutch.I almost never do it in a car.)

Anyway, the chain whips down and over and settles on the 11-
tooth cog just fine, but the front shift from the 39 to the
53 is much slower and takes more fiddling. It doesn't seem
to matter whether I shift the rear cogs or the front rings
first, the chain just slaps into place nicely on the rear,
but the front sprockets let me show off my shifting skills.

I still think that a toothed pulley in a cage will shift a
chain from gear to gear more cleanly than the cage alone.
But since it's impractical on the front (as far as I know--
maybe someone will come up with a weird picture), I'm not
sure how to test my theory.

Carl Fogel

Rick Onanian said:

Also, the front derailer must shift the chain over a much
bigger distance between gears; I've never seen a rear jump
of more than 4 teeth, but in front it's common to have a
14 tooth difference from one gear to the next (39-53).

Some of the Shimano Megarange cassettes have bigger jumps
than that;
e.g. the 8-speed Nexave has a 26T/34T jump.

I had a bike with 73T/52T chainrings [1] and it shifted
rather poorly, even with the use of a Shimano bar-end.

[1] <http://www.ihpva.org/incoming/2001/wbone2.jpg>.

--
Tom Sherman – Quad City Area

Tom Sherman said:

[1] <http://www.ihpva.org/incoming/2001/wbone2.jpg>.

Holy [censored], I'm gonna have nightmares!

Bill "tossing, turning" S.

Rick Onanian said:

Also, the front derailer must shift the chain over a much
bigger distance between gears; I've never seen a rear jump
of more than 4 teeth, but in front it's common to have a 14
tooth difference from one gear to the next (39-53).

Some of the Shimano MegaRange cassettes have demented jumps
like 24/34 (cue Sheldon telling us why this is fine, really)
but indeed even that is less than a typical front change let
alone a 110bcd 52/34 style arrangement.
--
David Damerell <[email hidden]> Kill
the tomato!

last week. the worn pulley will allow chain to eat cage
abuse side plates disenfranchise CR's and generally annoy
the expletive deleted out of the rider spoiling the ride

Rick Onanian said:

I wonder when somebody is going to invent friction
brifters. It can't be that difficult; I can imagine
mechanisms for it myself; such mechanisms exist in a
million other devices.

What about the front Campy Ergo lever?

--
Greg Estep

Rick Onanian said:

I wonder when somebody is going to invent friction
brifters. It can't be that difficult; I can imagine
mechanisms for it myself; such mechanisms exist in a
million other devices.

What about the front Campy Ergo lever?

--
Greg Estep

Greg Estep said:

Rick Onanian said:

I wonder when somebody is going to invent friction
brifters. It can't be that difficult; I can imagine
mechanisms for it myself; such mechanisms exist in a
million other devices.

What about the front Campy Ergo lever?

Is it friction? I was under the impression that Campy levers
offered more trim (such as I requested) but were indexed,
not friction...but what do I know, I'm a mass-market Shimano
schlub. I use what came on my Giant TCR2 and don't feel
motivated enough to spend money changing it.
--
Rick Onanian

Rick Onanian said:

Is it friction? I was under the impression that Campy
levers offered more trim (such as I requested) but were
indexed, not friction...

they're not indexed, but nor are they friction. its a kind
of ratchet, each click moves the f/d a small amount .. it's
like 3 to 5 clicks per chainring (i have a triple). i (and i
would guess most people) like it quite a bit more than the
shimano setup. it's certainly not a true friction system
with an infinite number of locations. it's finite.
--
david reuteler [email hidden]