This article is from the Bicycles FAQ, by Mike Iglesias with numerous contributions by others.
From: Jobst Brandt <firstname.lastname@example.org>
Date: Thu, 10 Jan 2002 17:40:52 -0800 (PST)
Chain wear and care evokes never ending discussions, especially for
new bicyclists who are not happy with this dirtiest of bicycle parts.
This leads to the first problem, of whether there is a best (and
cleanest) way to care for a chain. There are several ways to take
care of a chain of which some traditional methods are the most
damaging to the chain and others work to prolong its life.
That grease on a new chain, fresh out of the package, is not a
lubricant but rather a preservative that must be removed, thrives in
bicycling myth and lore. This is nonsense because chains are used as
they are by manufacturers who ship bicycles ready to use. They can
order chains with any desired lubricant and this is what they use. If
there is too much on the chain, it can be wiped off.
At the outset the term "chain stretch" is technically wrong and
misleading. Chains do not stretch, in the dictionary sense, by
elongating the metal through tension. They lengthen because their
hinge pins and sleeves wear which is caused almost exclusively by road
grit that enters the chain when oiled. Grit sticks to the outside of
a chain in the ugly black stuff that can get on ones leg, but external
grime has little functional effect, being on the outside where it does
the chain no harm. Only when a dirty chain is oiled, or has excessive
oil on it, can this grit move inside to causes damage. Commercial
abrasive grinding paste is made of oil and silicon dioxide (sand) and
silicon carbide (sand). You couldn't do it better if you tried to
destroy a chain, than to oil it when dirty.
Primitive rule #1: Never oil a chain on the bike.
This means the chain should be cleaned of grit before oiling, and
because this is practically 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 on the bicycle, do a fair job but are messy and do not
prevent fine grit from becoming suspended in the solvent. External
brushing or wiping moves grit out of sight, but mainly into the
openings in the chain where subsequent oiling will carry it inside.
Do not use gasoline because it is explosive and contains toxic light
petroleum fractions that penetrate skin. Removing the chain from the
bicycle isn't always possible. There are times (after riding in the
rain) when a chain screams for oil and good cleaning is impractical.
In that case rule #1 may be violated for humanitarian reasons.
However, only an internally clean chain squeaks, so it isn't as bad as
it sounds. Also, water is a moderately good lubricant, but it
evaporates soon after the rain stops.
Removing solvent from the chain after rinsing is important.
Compressed air is not readily available in the household nor is a
centrifuge. Manually slinging the chain around outdoors works best if
the chain is a closed loop but without pressing the pin completely in.
The other way is to evaporate it. Accelerated drying methods by
heating should be avoided, because they can be explosive.
Lubricating the chain with hot 90W gear lube works but it is also
efficient fly paper, collecting plenty of hardpack between sprockets
and on the outside of the chain. Motor oil is far better, but
motorcycle chain and chainsaw lubricants are better yet, 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. This becomes apparent with any
water that gets on the chain. It immediately squeaks.