DougG

On my Sora-equipped road bike, the RH shifter cable loops around to the cable stop on the left side of the downtube, and the LH shifter cable seats into the stop on the right side. But the guide under the BB is configured so that the FD cable is on the left while the RD cable passes through on the right. This means that the cables running along the downtube cross in a shallow X between the cable stops and the BB.

Is this the usual way of routing these cables? Obviously, if I routed the shifter cables to the nearest stops (L-L and R-R) so that the cables both run straight along the downtube, they would be making a tighter bend, but would this be violating any rules?

I'm redoing my drivetrain soon and will have the chance to make changes at that time. Is there any reason to do so?

roadfix

They could be routed either way. Are the cables crossing underneath the down tube rubbing the paint? I would route them whichever way creates lesser binding of cables.

HillRider

The more normal cable routing is left-left and right-right. However, What you have on your bike is sometimes done to keep the shifter cable housing from rubbing on the head tube when the bars are turned fairly sharply.

Older bikes with the cable stops mounted on downtube shifter bosses benefited from this and it saved the headtube paint. Newer frames with the cable housing stops "brazed-on" to the head tube or high on the downtube don't need or benefit from this routing.

tellyho

I have said older bike with L-L, R-R routing. It does rub on the headtube, but I prefer that to crossed cables.

JunkYardBike

It's always best to route cables and housing so bends are gradual. Tight bends = increased friction = less than optimal shifting, especially on indexed systems. Sheldon Brown recommends the X pattern for DT cables on some setups for this very reason: https://sheldonbrown.com/cables.html#crisscross