Q&A: Replacing BB cable guide

QUESTION:
Hey Jim, I just noticed that my cable guide located beneath the bottom bracket of my road bike is partially broken (rear side). I've ordered a new one, should be here in a day or two. It looks pretty simple to replace, just unscrew and switch them out but on a closer look I noticed that the cables need to be threaded through the cable guide. I was hoping to be able to do this myself, however I'm not sure if I'll need additional parts, etc.

Can you walk me through this as I have never removed the cables myself. Also, would it cause any damage to the bike or potentially myself to ride it with the cable guide partially broken?
Thanks Jim,
Cherisse

ANSWER:
First off, the cable guides are almost always made of plastic so it shouldn't do any damage to keep riding on yours until you can replace it. You should look closely to make sure that nothing is wearing on the cable that might cause it to fray, weaken and break over time, but since the guide is plastic, it's probably just fine and you might not even want to worry about replacing it.

If you want or need to replace it, depending on which type you have, you should be able to install it without doing anything with your cables. This would be the case if the guide is 100% plastic. On this type you should be able to modify the guide so that the cables fit in and out of the grooves without cable removal. To do this you just put a thin slot in them with a sharp knife (be careful), a hacksaw or a thin file. If you add a slot like this, you'll be able to install the guide and then slip your cables through the slots and they'll snap back in place.

Since the cables are always pulled up tight during shifting there's little risk that they will ever get out of the guide slots so this should work fine. Of course to remove the old guide you'll want to add slots, too. That'll give you a chance to practice your slotting technique.

Most cable guides on my bikes are designed so you don't need to remove the cables to install them. So by modifying yours like this you'll actually be upgrading your bike. It's never a good idea to remove cables unless you really need to.

Have fun!
Jim