Question: Other than providing a “clean” look, what is the advantage of internally routed cables? I was under the impression that putting a hole in a tube weakened it and it let in water. I also thought that standing water in a tube, no matter the material, was not a good thing.
Thanks, Larry H
Jim Langley’s Answer: That’s a great question, Larry, thanks,
When they put holes in tubes in order to run the cables inside, they reinforce the tube at the holes so that the tube is as strong as it was before and can’t fail at that point. Depending on the frame material, it’s done different ways. It won’t weaken the frame if it’s done well.
Water gets inside frames regardless of whether or not there are holes for cables. All frames have vent holes in various places designed to let the water get out. But, with steel frames, we know that water can damage the steel and eventually rust out and ruin the frame. So, a builder making a steel frame will try very hard to prevent moisture entry.
With aluminum, titanium and carbon frames, the water won’t do any damage and as long as it can drain out, it will only collect and add a little weight for a short period of time. So standing water is bad from a sloshing around and adding weight point of view but it shouldn’t harm the frame. And any components it comes in contact with should be lubricated which should prevent corrosion.
Ideally, though, the water gets out of the frame almost as fast as it gets in. This isn’t always the case. If you work on bikes you will see water at the bottom bracket a lot of times – especially on mountain bikes where they ride through creeks, etc.
I’ve even seen rims full of water. Riders often have no idea it’s in the bike.
Besides the clean look, a cable running inside the frame is protected by the frame. Outside it can be more likely to rust, fray and fail. But, internal cables have to be done right. If not, the outer cable routing will still be superior and easier to maintain, too.