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:

I
used to ride with Mr. Bullseye, a very nice man, but 35 years have erased
his name from my recall banks.

Rodger Durham.

And you replace jockeys when they stop winning.
Phil Brown

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

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]