Originally Posted by
crispy010
I run my cables so they cross under the down tube and it does not affect functionality - the cables don't touch each other at the cross point, and the angles are so shallow as the cables go into the BB guide that it makes no difference.
In my opinion crossing the cables makes a much cleaner-looking installation.
I have a crossed-cable setup and the bare wires do just touch. I bet, though, that the friction of one wire touching the other at that angle is so small that is could hardly be measured, and you get the benefit of a less sharp S-bend where the cables meet the down-tube stops.
Does it really affect the shifting, though? I've tried both setups on the same bike and could not tell any difference. I think that modern cables and outers are so good that it doesn't matter.