Soak the rubber bung in hot water for 10 minutes before fitting
Here’s how to re-fit rubber cable bungs on internally routed frames. Not glam, but really useful if you want to keep a quiet, clean and well-serviced bike.
How to fit a rubber cable bung
- Soak the rubber bung in hot water for 10 minutes before fitting.
- Endure you orientate it correctly, so that it sits flush against the frame tube at the right angle.
- Hook the front edge into the frame and press down.
- Work your way back, levering in the bottom of the bung as you go.
- Push the bung forward and lever in the last section. Again press down so it seats correctly.
Having all your cables and hoses on the outside of your frame means you can access them easily for servicing, upgrade or replacement. However, if you have a profusion of cables — like a dropper remote, brakes, gears and a lockout — it can start to look like a tangled mess. The solution is to route them all inside the frame, which makes the bike look cleaner, but this often presents its own set of problems. Routing cables through bikes can be really easy, or infuriatingly hard; and internal routing often demands rebleeding your brakes or adjusting the gear cables so they pull smoothly.
If you’ve just bought a bike that’s internally routed, the first things to get your head around are the cable ports — in other words the entry/exit points for your cables. Most manufacturers use a rubber insert at this interface, and while this is often factory fitted, if you have to do any servicing, it can be a frustrating job getting them back in place. Whyte Bikes has a little tool to help make fitting rubber inserts a lot easier — it’s a cross between a tyre lever and one of those pry tools for opening your phone case, and is designed to push the bottom of the insert into the frame. To make the job easier, Whyte recommends soaking the rubber bung in hot water for several minutes to make it pliable. This works to a degree, but you’ll still need to employ a bit of brute force to seat it properly.
Some manufacturers use a hybrid insert, which is part bolt-in, part press-fit. Trek employs this style of cable management in its frames and it’s neat and dead easy to remove. Companies like Specialized, Cannondale and Voodoo use a bolt-in insert, held in place by a small Allen bolt. It’s easier to fit than any of the ones above but you have to be careful not to damage the threads.
Whatever insert you have, you will need to buy a like-for- like replacement — leaving the frame bare is less of a faff and cheaper but it doesn’t look pretty and you run the risk of water and dirt ingress.
Routing the cables is where it potentially really gets tricky, because you have to thread a floppy cable or hose inside the frame without being able to see what you’re doing. Fortunately, Park Tools makes the Internal Routing Kit to make things easier, and while it costs £50 it is a must-have toolkit item in our view. The kit is made up of plastic coated cables with magnets and fittings at the ends. Then there’s an external magnet to let you ‘pull’ the Park guides through your frame, tracing their path from the outside, before attaching and dragging through the real cable or hose. The newly-updated kit even includes a dedicated E-tube Di2 cable connector to fit through a 6mm frame hole.