About a 2000-model Specialized Stumpjumper FSR,
when the seatpost length is set to stick out just a bit from the frame,
the front shift outer cable (depending on its length)
can sometimes interfere with the bottom of the seatpost.
Through years of use in that state, I've actually seen
the bottom of an aluminum seatpost
get worn smooth as if a round file had been run across it,
shaped perfectly to the outer cable's diameter.
Oddly enough, the outer cable itself wasn't worn at all.
It's not the case that the outer cable was actually getting worn too,
but I just happened to see it right after it had been replaced.
I remembered that today while working on
a flatbar hybrid with hydraulic disc brakes and mechanical shifters.
The routing order of the outer cables was poorly arranged,
and the outer cables were pressing against each other in contact.
At the spot where the shift outer and brake hose
are constantly rubbing hard against each other,
the shift outer's covering had been worn away,
but the brake hose was completely fine.
If it were the other way around, you'd risk brake fluid leaking—
so the softer file wins! They clearly understood this principle when routing it this way.
As I'm writing this, I remembered one more thing.
In the front caliper brake situation too (→here), the outer comes out on top.
The story in that link about "the seatpost getting worn from rubbing against the outer at the Ohtaki 1 race"
wasn't on the Stumpjumper at the beginning, but on a Gary Fisher Excalibur.
when the seatpost length is set to stick out just a bit from the frame,
the front shift outer cable (depending on its length)
can sometimes interfere with the bottom of the seatpost.
Through years of use in that state, I've actually seen
the bottom of an aluminum seatpost
get worn smooth as if a round file had been run across it,
shaped perfectly to the outer cable's diameter.
Oddly enough, the outer cable itself wasn't worn at all.
It's not the case that the outer cable was actually getting worn too,
but I just happened to see it right after it had been replaced.
I remembered that today while working on
a flatbar hybrid with hydraulic disc brakes and mechanical shifters.
The routing order of the outer cables was poorly arranged,
and the outer cables were pressing against each other in contact.
At the spot where the shift outer and brake hose
are constantly rubbing hard against each other,
the shift outer's covering had been worn away,
but the brake hose was completely fine.
If it were the other way around, you'd risk brake fluid leaking—
so the softer file wins! They clearly understood this principle when routing it this way.
As I'm writing this, I remembered one more thing.
In the front caliper brake situation too (→here), the outer comes out on top.
The story in that link about "the seatpost getting worn from rubbing against the outer at the Ohtaki 1 race"
wasn't on the Stumpjumper at the beginning, but on a Gary Fisher Excalibur.