BB cable guide for switching cables?

[cgolvin]

As i was reading @XXtwindad's entertaining thread on his Firefly and saw the commentary about "correct" cable routing with derailleur cables crossing under the downtube, it got me thinking.

Why not make a BB cable guide that does this crossover? Has anyone ever seen such a thing, whether as a product or maybe 3D printed? I wonder whether this might negatively affect shifting, since the turn in the cables would be more abrupt than the gradual transition along the downtube.

Just curious.

[ultraman6970]

Some people crossed the cables because they say the shifting is better.

THe cable comes out and then you route it to the opposite side of the boss or frame, then you cross it to the right position.

If you have a frame with internal cabling then you could be crossing that thing twice if you arent paying atention.

I do not see the sense to it because at the end u end up scratching the downtube with the cable because the cables will be touching under the downtube of a vintage steel bike of a carbon or aluminum frame with non internal cable routing. To me that's more than a reason for not doing it.

Some guys do it just because is their style too.

[jtbadge]

I've never been able to cross the cables underneath without having them rub the downtube. Also curious if there is a different BB guide to facilitate this, or if it just needs a shim/spacer.

[robt57]

I do it when I can. What I mean is when cables cross away from the DT, not close. I like keeping the housings from crossing past the headtube and will do so when feasible.

I crossed cables in my first internal build unwittingly. Felt like there was not much witty thinking involved when I figured out why the rear shifed a gear along with a big ring shift.

Originally Posted by ultraman6970

Some people crossed the cables because they say the shifting is better.

THe cable comes out and then you route it to the opposite side of the boss or frame, then you cross it to the right position.

If you have a frame with internal cabling then you could be crossing that thing twice if you arent paying atention.

I do not see the sense to it because at the end u end up scratching the downtube with the cable because the cables will be touching under the downtube of a vintage steel bike of a carbon or aluminum frame with non internal cable routing. To me that's more than a reason for not doing it.

Some guys do it just because is their style too.

[semdoug]

I used to cross cables under the down tube but that was only with down tube shifter bosses/stops. Have not found it to work when the bosses/stops are on the head tube, the cables contact the down tube too much.

[AngryScientist]

i do this on every bike. it has never been an issue with a "normal" cable guide.

you can kind of see here, nothing touches the DT:

[cgolvin]

[Edit: composing while Angry posted the above.]

Sorry, I guess I wasn't clear in my original post. This does not pertain to frames with internal routing.

I too have stayed away from routing cables the "wrong" way (i.e., FD on the drive side, RD on the non-drive side) because I'm concerned about the cables rubbing under the downtube, either against each other or against the tube itself.

Therefore my idea was to use an altered cable guide under the BB to do the re-route -- I visualize an "X" where there is an overpass at the cross to prevent the cables from rubbing against each other. I was wondering whether anyone had ever produced such a cable guide, either as an actual product for sale or a (e.g., 3D printed) DIY rig.

[Velocipede]

Originally Posted by jtbadge

I've never been able to cross the cables underneath without having them rub the downtube. Also curious if there is a different BB guide to facilitate this, or if it just needs a shim/spacer.

They make a double tall bottom bracket cable guide. It's usually found on cheaper bikes. Sometimes you can find them on Amazon or Ebay.

[Mark McM]

When you have the cable guides on the head tube, and the head tube is short (and the stem is slammed) like on my bikes, not crossing the cables results in excessive bends in the cable.

As far as cables rubbing against the down tube, there's several potential solutions:

• Use rubber cable donuts on the cables
• Use cables with continuous liners (like those made by Gore, SRAM or Jagwire)
• Use frame protection tape on the bottom of the downtube
• Any combination of the above