What is the best lubricant to use to keep my drivetrain rolling smoothly? Also, should I oil my rear derailleur pulleys? Where is the greatest source of friction in my drivetrain?
-Geoffrey Sinclair: Kent, Washington

When it comes to chain lubricants, there are as many theories as there are brands of chain oil. The truth of the chain oil mystery lies in how a chain operates when it is under load-and what it does elsewhere. Before we enter into this politically charged realm, let's explore a little.

One link is actually a pair of outer and inner side plates, riveted together by hardened-steel pins. The outer plates serve only as connectors and, because they are the widest part of the chain, are the first piece of the chain to hit the shifting aids (pins and ramps) on the cogs and chainrings. The inner plate assemblies ride on the sprockets and if you look closely, you'll see that they have a bushing pressed into each end that traps a roller which spins between plates and contacts the sprocket teeth.

Because the inner links have the internal moving parts and are the only place where the chain contacts the sprockets, this is the only place where there needs to be oil-and not much of it. You should not be able to see oil on the outside of a properly lubricated bicycle chain. Why? because the real enemy of a chain is dirt-which will cause more friction than oiling it can save you. Oil attracts fine particles of grit that work their way into the chain and, under tension, slow you down while they grind away at your expensive sprocket teeth and chain.

I apply a lightweight synthetic oil (choose a bike-branded one if you want-I use Mobil One), one drop at a time to the inner rollers. I work it in by spinning the cranks slowly for a minute (don't fling oil all over the bike), and then I wipe the sprockets, chain and rear derailleur pulleys clean and dry with a towel. When I am done, the chain doesn't look as if it was lubricated at all. When I return from a ride-my drivetrain and frame don't appear "lubricated" either.

Tip: The drier the dry lubes, and the waxier the wax-lubes are, the more often you will need to use them, as they don't go the distance.

Only one tooth close to the top-center of each sprocket is under load at any given time. The rest of the links around the sprocket are along for the ride. When the chain approaches the turning sprocket, the roller eases the link onto a sprocket tooth and the link rotates ever-so-slightly to match the diameter of the sprocket. Once the roller is seated against the sprocket, there is no further movement, the chain is stationary until it is released at the opposite side of the sprocket. Watch the chain articulate as it enters the sprockets and you'll realize how little movement there is between the link and its internal parts. Notice that, the larger the sprocket is, the less the chain has to bend as it engages the teeth.

Tip: Avoid using the 12-tooth cog if you can duplicate your gearing by using the big-ring and a larger sprocket in the middle of the cassette.

So, where is the friction?  We already covered grime as a source of drag, but there are two more drag-producers in a derailleur drivetrain that should be tended to: side-loading of the chain, and the rear-derailleur pulleys.

Grab a short length of chain and wiggle the links. It will move freely. Now put a side load on it and do the same test and it will bind severely. When you cross-chain (big chainring/largest cog, or vice-versa), you force the outer-link and inner-link sideplates against each other and that creates a huge drag component.

Tip: Don't be afraid to cross-chain when you need to grab a gear in a hurry. You should use every gear combination on your bike-just switch back to a low-drag gear selection that keeps the chain and sprockets properly lined up when you are out of trouble.

The second source of drag are the two pulleys on your rear derailleur. There is no load at these points, but the jockey pulleys rotate significantly faster than any other part of the bicycle-and the tiny pulley sprockets force the chain links to quickly articulate over 90 degrees in opposite directions. Here is a place where ceramic bearings are a perfect application, because the radial loads are small, and rolling resistance is the major culprit. Here also is a case for using lightweight oil, because the chain links swing rapidly through a sharp arc, but under no load-so waxy or sticky lubricants will only cause drag.

Tip: Keep the jockey pulleys squeaky clean. Check the pulleys when the chain is removed. If they don't spin freely, replace them or eliminate the source of friction.

For any chain-related questions, complaints, or for any RBA reason, visit Richard Cunningham at AskRC@roadbikeaction.com