Originally Posted by
xiaodidi
My rule:
Chain skips - lube it
Still skips - replace it
No rulers, no gages, no wasted $'s
Every bit of aluminum on your bike is rusted - FACT. Are you running to the store to replace it ?
Anodising is a somewhat different chemical reaction to rusting/oxidisation, wherein the molecules are all lined up vertically, I think, and provide a hard layer that is resistant to oxidation. Most items bought as new on a bicycle are anodised to prevent oxidation.
If a chain skips, it is time to replace *it* and likely the rear gearset as well as the chainrings. Lubing a skipping chain has absolutely no influence over the change in pitch that wear has caused... and that causes chain skip (given all other adjustments are correct).
It's also worth pointing out that a chain and gears that wear evenly together, across all gears (that is, you don't heavily favour a particular ratio) will enable most riders to go longer without having to replace a chain. Yes, at the end of, say 12,000 or even up to 15,000km, you may need to replace everything, but that's still a lot of riding for most people -- probably a couple years worth. And yes, it probably helps to use 6, 7 or 8 speed systems that have a slightly beefier chain.
My personal experience is an 8sp Sora set-up on a brand new Merida road bike I had earlier this decade that did around 11,000km and still had plenty left to go. The chain and cogs were cleaned fairly regularly. It was a double up front.
The accepted change in pitch (erroneously called stretch by people who don't know any different) over *12 inches* is between 1/16th and 1/8th of an inch. Use the 1/16th figure if your cogs and rings are still in good shape, but generally replace the lot if you go to 1/8th.
Of course, theory often is somewhat different from practice, as I have demonstrated above.