Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: 12 links + 12 inches +1/8 rule question...
Date: Wed, 17 Jan 1996 02:24:21 GMT

Eric House writes:

> Here's another data point: The Rholoff "Chain Wear Indicator" I use (and
> highly recommend) has one side intended for chains being used on alloy
> cogs and another for chains on steel cogs.  The alloy side is supposed
> to tell you when the chain is stretched .075mm/link, or about 1/14" over
> 12" (24 links).  The steel side rejects a chain with .1mm/link, or about
> 1/10" over 12".  Chains being cheap and good freewheels increasingly hard
> to find, I use the alloy side even though I'm running steel cogs, and have
> never had a new chain skip.  This after many chains on the same freewheel.

How about using the term "worn" rather than "stretch".  For those who
are new to the subject of chain wear, this might reintroduce the
concept that the links of chains, like plastics, become longer under
tension and that it is a matter of time, not wear.

The Rholoff chain measuring tool makes some invalid assumptions
because it includes the roller clearance in the measured link pin
wear.  Roller clearance is not uniform among chain manufacturers and
can grow faster or slower than the chain elongation, depending on
method of chain "care".  The Rholoff gauge measures between two
rollers a several links apart.  Because rollers always have clearance,
they can be displaced longitudinally on the chain.  Roller clearance
is not important to chain performance while the pitch of the links,
pin to pin is.

I assume Rholoff made this tool because inch rulers are no longer
available in central Europe, even carpenters no longer use them.
Thus, holding a ruler next to the chain, as we do here, is no longer
an option.  Instead of making a chain ruler, they chose to make this
complex tool.  A ruler measuring over 12 inches, even non contacting,
is more accurate and easier to use than this tool.  Until you've tried
the ruler method, it is not obvious how easy it is to see a 1/16 inch
wear in a foot by holding a yardstick next to the bottom run of the
chain.

One of the things that is not readily apparent, is that the wear is
twice as bad as what you measure because only every second roller is
out of pitch, the two rollers on an inner link are always 1/2 inch
apart.  The elongation occurs in the pins and sleeves only.

Jobst Brandt      <jbrandt@hpl.hp.com> 

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: How often do you need to change your chain?
Date: 12 Sep 1996 03:25:58 GMT

Diane L B writes:

> I've heard conflicting numbers from 1000-15000 miles...so which is
> it?  For the record, I'm asking about a road bike that I try to keep
> out of the rain (though I've gotten caught in a storm or two).

That's what the FAQ is for, to answer Frequently Asked Questions.
----------------------------------------------------------------------
Subject: 8.6  Wear and Gear Slippage
From: Jobst Brandt <jbrandt@hpl.hp.com>

Chain care and chain wear seems to be a never ending discussion,
especially for new bicyclists who are not entirely happy with this
dirtiest of all parts of the bicycle.  This leads to the first problem
of whether there is a best (and cleanest) way to lubricate a chain.
There are a number of ways to take care of a chain, of which some
traditional methods are the most damaging to chain life, while some
work to prolong life.

Although to some it may seem redundant to repeat, let me repeat it.
Chains don't stretch in the sense that the metal elongate, but
lengthen because the parts wear.  Wear in the pins and sleeves change
the length of the chain as the pins fit more loosely.  The wear arises
primarily from road grit that enters the chain when it is oiled.  Grit
on the outside of a chain is the ugly black stuff that gets on your
leg.  This dirt has little effect on chain function because it can't
get inside to do damage.  Only when a dirty chain is oiled or has
excessive oil on it does this grit get inside where it can cause
damage.  Commercial abrasive grinding paste is made of oil and silicon
dioxide (sand) and silicon carbide (sand).  You couldn't do a better
job if you tried to destroy a chain than to oil a dirty chain.

Primitive rule #1:  Never oil a chain on the bike.

This means the chain should be cleaned of grit before oiling it.
Because this is essentially impossible without submerging the chain in
a solvent bath (kerosene or commercial solvent), it must be taken off
the bicycle.  Devices with rotating brushes, that can be clamped on
the chain when on the bicycle, do a fair job but are messy and do not
prevent fine grit from becoming suspended in the solvent.  Do not use
gasoline, because it is highly explosive and contains toxic light
petroleum fractions that penetrate the skin.  Removing the chain from
the bicycle isn't always possible, and there are times (after rain)
when a chain screams for oil and a good cleaning is not practical on
the road.  That is when rule #1 must be violated.

Removing the solvent from the chain after the rinse is important.
Compressed air is not readily available in the household nor is a
centrifuge.  You can go outdoors and sling the chain around.  This
works best if the chain is a closed loop.  The pin needn't be pressed
in for this.  The other way is to evaporate it.  Accelerated drying
methods should be avoided because they can be explosive.

Heating the chain and applying 90W gear lube works, but highly viscous
oils acts as efficient fly paper, collecting plenty of hardpack
between sprockets and on the outside of the chain.  Motor oil is far
better but motorcycle chain lubricants are even better because they
have volatile solvents that allow good penetration for their
relatively viscous lubricant.  Paraffin (canning wax), although clean,
works poorly because it is not mobile and cannot replenish the bearing
surfaces once it has been displaced.

Upset collar chains

Sedis was the first with its Sedisport chain to introduce upset
collars on the side plates to replace full width sleeves on which the
rollers and pins bear.  Although the strongest and one of the lightest
chains, it achieves its light weight at the expense of durability.
These chains, now practically the only ones available, have only
vestigial sleeves in the form of short collars on the side plates to
support the roller on its outside and the link pin on the inside. This
design is both lighter and stronger because the side plates need not
have the large hole for insertion of sleeves.  Because MTB's use drive
sprockets as small as 18t that can cause extremely high chain loads,
pin and sleeve chains would be at a disadvantage to safely withstand
such loads.

Normally the inside of the sleeve on conventional chains was well
protected against lubricant depletion, because both ends were covered
by closely fitting side plates.  On some motorcycle chains these even
have seals at each end.  In the upset collar design there is no sleeve
while the side plates are formed to support the roller and pin on a
collar with a substantial central gap.  In the wet, lubricant is
quickly washed out of pin and roller and the smaller bearing for the
pin and roller often gall and bind.  Although in good weather this is
not a problem this type of chain has feet of clay in the wet.

Chain Life

Chain life is almost entirely cleanliness and lubrication related
rather than load related.  For most bicycles the effect of load
variations is insignificant compared to the lubricant and grit
effects.  For example, motorcycle primary and timing chains, operated
under oil in clean conditions, last years while the exposed rear
chains must be replaced often.

The accurate way to test whether a chain is worn is by measurement.  A
new chain has a half inch pitch so that it has a pin at exactly every
half inch.  As the pins and sleeves wear, this spacing increases and
becomes damaging to sprockets.  When the chain pitch grows over one
half percent, it is time for a new chain.  At one percent, sprocket
wear progresses rapidly because this length change occurs only between
pin and sleeve so that it is concentrated on every second pitch.  The
pitch of the link containing the rollers remaining constant.  By
holding a ruler along the chain on the bicycle, align an inch mark
with a pin and see how far off the mark the pin is at twelve inches.
An eighth of an inch (0.125) is a little over the one percent limit
while more than a sixteenth is a prudent time to get a new chain.

Skipping Chain

That a new chain does not want to engage used sprockets may be
obvious, but in theory a new chain cannot freely engage a new rear
sprocket under load even though it has the same pitch as the chain.
That is because the tooth being engaged would be under load and this
is a contradiction in itself.  Therefore, a slightly worn sprocket,
that has pockets in its load bearing face is even more reticent to
engage a new chain with perfect 1/2 " pitch.  

Sprockets, by the way, do not change pitch when they wear, only the
tooth form changes because the number of teeth remains the same and
the base circle remains essentially unchanged for normal sprocket
wear.  On fixed gear bicycles that are ridden until the chain is 5%
out of pitch, the base circle may be slightly reduced but this only
makes the fit of a new chain worse.

Without a strong chain tensioner or a non derailleur gear, the chain
has insufficient tension on its slack run to engage the sprocket when
under tension.  In contrast, engagement on the tension side, as on the
crank sprocket, generally succeeds even with substantial tooth wear
because the tension encourages engagement.  This condition, however,
enhances "chainsuck", the failure of the chain to disengage the
chainwheel.  This can generally not occur without a long arm
derailleur, common to most MTB's and therefore, road bicycles normally
experience a grunchy disengagement instead of a chain jam.

A new chain has a pitch of exactly one half inch.  A sprocket, worn by
a longer pitch (worn) chain, has hooked teeth but with the correct
pitch.  The hooked profile is formed by the rollers of a worn chain as
they exit the sprocket under load, whereas rollers of a new chain with
correct pitch exit under no load because the load is transferred to
the next roller before disengagement.  However, with hooked sprockets
the new chain cannot engage under load because its pitch doesn't allow
it to get over the hook and into the next pocket.  These differences
are only a few thousandths of an inch but enough to prevent engagement
when the previous roller is fully engaged.

As a chain wears it concentrates more of its load on the last tooth of
a sprocket before disengagement because the chain pitch no longer
matches the pitch of the sprocket.  This effect sometimes breaks off
sprocket teeth.  The load concentration on the sprocket also
accelerates wear and is another reason to replace a chain at 1/16th
inch wear.

Jobst Brandt      <jbrandt@hpl.hp.com> 

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Rim failures
Date: 16 Jun 1998 15:48:33 GMT

Tom Kunich writes:

> The mechanical stress from thermal loadings on pipelines like those
> in Alaska exceed the stresses on bicycle joints from what I've heard.
> And the fatigue loadings from these stresses are more important.

If the bicycle part fails and the pipeline doesn't, then the stress is
definitely higher in the bicycle part.  This sounds like claiming the
hull of a battleship is stressed more than a bicycle spoke, just by
association with size and cost.  The comparison is BS.

> I suggest you hang around. Jobst has told us about regularly
> breaking spokes, rims, bottom brackets, as well as wearing out brake
> pads at a rate far greater than the rest of us. He has told us of
> breaking frames, headsets and virtually every component on a
> bicycle. On the other hand he appears to get tremendous chain
> mileage.

Not anymore.  I used up my last convetionally sleeved chain a year ago
after more then 20000 miles.  Now I'm down to Sachs (4 part chains)
that wear out at the thought of rain and gall if they happen to run
dry on a rainy day.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jobst.brandt@stanfordalumni.org
Subject: Re: chain cleaning
Newsgroups: rec.bicycles.misc
Message-ID: <pt8Fa.1049$%3.93535@typhoon.sonic.net>
Date: Mon, 09 Jun 2003 23:10:13 GMT

After reading the FAQ item:

http://draco.acs.uci.edu/rbfaq/FAQ/8d.2.html

I noticed there is still something missing and that FAQ, that being
"What is that ugly black stuff on the chain?"  It is worn chain steel,
almost all of which comes from pin and sleeve wear, the wear that
shows up as pitch elongation.  A chain that doesn't produce black
particles is a chain that does not wear.  The rate of wear being
primarily dependent on how clean the chain is internally.  It has
little to do with external cleanliness, the place that gets the most
attention on chains.

Jobst Brandt
jobst.brandt@stanfordalumni.org
Palo Alto CA

From: jobst.brandt@stanfordalumni.org
Subject: Re: Chain Maintenance
Newsgroups: rec.bicycles.tech
Message-ID: <Xb9zc.16792$Fo4.216925@typhoon.sonic.net>
Date: Mon, 14 Jun 2004 03:45:59 GMT

Patrick Lamb <pdl678NOSPAM@comcast.net> writes:

> I don't doubt that your bicycle gets dirty but the chain (unless you
> are riding on dirt) is pretty clean.  In fact squeaky clean.

> I dislike a rainy commute precisely because the outside of my chain
> is filthy afterwards.  I don't think the roads where I live are
> particularly dirty, as roads go, and they certainly are paved.  I'm
> curious how you can ride in the rain and end up with a squeaky clean
> chain.

I mean that literally not figuratively.  The chain will be washed out
and retain no oily solvent so it will be squeaking as soon as it dries
out.  There being no oil or grease, brushing the sand off the outside
is trivial because it easily falls off when running a rag over the
back-pedaled chain.

It's much like a shoddy steam cleaning with non sticky residue on the
outside.

Jobst Brandt
jobst.brandt@stanfordalumni.org