On Tue, 18 Nov 2008 09:15:27 -0700, slide may
have said:

As I mentioned, I just got a Rans CF bike and am enjoying it quite a
bit. A friend of mine got his last spring. So far he has about 2,500
miles on it (4.000 kms).

He mentioned that the Rans doesn't wear chains or sprockets like
conventional bikes. He said he has no appreciable chain wear over that
period where he'd have at least detectable wear and maybe a new chain
needed if it were a conventional bike. He said the reason was the longer
chain meant less stress per link thus less wear thus the entire drive
train lasts longer.

I can't see it. Take a chain of 10 links. Suspend it from an overhead
and hang a 30 kg mass from it. The stress per link is 30 kgs plus a bit
for the mass of the chain links downstream. Now take the same setup, but
make the chain 40 links. IMO, the stress per link is the same.

I can't deny his chain is almost new after 2,500 miles but I am having a
tough time believing it's due to the longer throw between chain ring and
cassette on the Rans compared to conventional bikes.

Am I missing something?

Yes. Chain wear is not from linear strain, but from flexure and
rub/roll on sprocket teeth. Each link on a long chain makes fewer
trips around each end of the drivetrain than a shorter chain would, so
wear is less per link. Sprockets wear more quickly when run with a
worn chain, so the wear rate reduction carries over to them as well.

This does not mean that adding links to your correctly-sized
conventional-frame bike's chain will make it last appreciably longer;
the cited effect is due to the dramatic length difference in the
radically crank-forward layout of the 'bent.

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