Bottom bracket cable guide. Are there different angles?
 

In converting a flat bar road bike to drops I have almost all my questions answered except for something I just noticed. The bike has a Deore FD and the cable routes under the shell of the bottom bracket, runs straight up along the seat tube, around a pivot on the derailleur, then 90 degrees out to the clamp bolt. I have a Tiagra FD I want to throw on there but it does not have that pivot point, which means the cable will go off at an angle from the guide directly to the clamp bolt on the FD. Is there an issue here with how the cable will run through the guide? Will there be excessive where on one side of the guide and do I need to find one that will direct the cable properly to the FD?

Have you considered a Bike shop survey, ? go to the shop and look at a variety of bikes and see..


they used to run above, alongside the BB, now almost universally the guide is under the BB.

Housing stop for RD is accordingly, above or below the back end of the chainstay..

Good idea.

It'll be fine.

Shimano manufactured a few derailleur models that are designed to work with either top pull or bottom pull frames. It sounds to me like your Deore is one of those. Your bottom pull Tiagra derailleur will work fine without the roller.

One situation that might cause problems is when the chain is on an outer ring, you shift the lever to a lower gear, but hesitate before you actually pedal and engage the ring onto that lower ring. At that point, you've created enough slack in the cable to allow it to slip off the side of the guide. When you pedal forward, taking up the slack in the cable, the cable might be riding on top of the guide's "wall". How you've got more tension on the cable and you might get chain rub along the inner derailleur cage. I've had this issue come up with certain models of Diamond back bikes I've built.