If you look at where brake and cable housing enter our frames, there is a plastic “door”. Behind the door you’ll find a rubber grommet. This grommet, while simple, holds the housing that enters it in place so that internally routed cable and brake housing doesn’t move or rattle while riding rough terrain.
These grommets are not left or right specific. Knolly includes a few options of these rubber grommets with every frame to hold housing combinations of 4mm + 5mm (shift + brake) or 4mm+4mm (shift + dropper) or 4mm on its own, allowing customization.
At the back of the bike, where the seat tube flares for the core FourBY4 suspension pivots, is the exit location of the brake and cable housing. There is a rubber gasket in this location that works like the front grommet, holding the housing in place and also preventing rain and dirt from entering the frame. While the location is in direct fire of trail debris, it is protected with a bolt down a metal plate to protect the rubber gasket and provide a more secure fit for the housing.
These two grommet/gasket locations work together to secure the housing within the frame and prevent any rattling or noise.
Comment
Unfortunately the plastic “door” is hard to replace if it breaks. A brake hose with an olive won’t fit through the opening. I had to sand down the opening hole so that there was a bit more room to squeeze through. Maybe the ‘door’ could be made of a harder rubber with a slit underneath the opening, to insert the cables?