Actually Nobby, the link I was referring to was older than that and had the link that fishercat posted to WebBike World, or whatever it's called. That has some really good pix of the results of using WD40 on a chain.....
And to make a short story long....
I posted this awhile ago, maybe even on the old boards..
Chains 101:
What Sandmann posted above about the lube in the chain is absolutely correct. The longer it stays in there - uncontaminated and undiminished, the longer your chain will last. Once the internal lube starts to get past the seals, or dirt goes in past the seals, the internal wear between the pins and bushings will accellerate, and you will be adjusting your chain more often. That is the "sign" - time to replace the chain and the sprockets. One way to check for that is to move the chain sideways. If there is any play or looseness then the chain is on it's way out.
External wear is a whole 'nother ballgame. It's gonna happen no matter what you do. That's the wear between the bushings on the chain and the teeth on both sprockets. As they are exposed to dirt constantly, over time the sprocket teeth are going to wear. The drive sprocket will wear on the rear side of the "root" (the valley between 2 teeth) while the driven sprocket will wear on the forward side of the root. Chain lubes help lube the seals, but some of them also hold the dirt which causes this type of wear. A mis-adjusted chain will accellerate this type of wear also. The solution for longest chain life would be an enclosed chain case with a proper lube installed to a proper level.
But, since that would look ugly as sin, we just have to learn to check , clean, and lube our chains once in a while..
