Originally Posted by
chasm54
All of this has been interesting and educational, mainly because of Barrettscv's input. I shall have to revise my prejudices against cross-chaining. I still think it is inelegant, though, so irrespective of its effect on chain wear I shall continue to avoid it. Notwithstanding your psychological benefits of climbing in the big ring, Hermes, I don't think I'm going to be able to persuade myself that the 53-25 is really much different to the 39-18.
It's not the chain wear that's at issue, it's the tooth wear, mainly on the chainring as the top run of the chain engages because that's where the major force is. It's also what causes the noise, not the chain by itself. There also is wear on the cassette teeth, but the derailleur is designed to help alleviate this.
If you want an example of how an askew chainline can upset things, get going on a poorly aligned fixed gear. A thrown chain will happen.
And your persuasion on using 53-25 on a double hinges on chain length -- if it's OK, you generally haven't got an issue.