What does a Carbon Steerer Fork Bung do?

[Hawk]

Can someone explain what exactly a steerer fork bung does?

Does it perform the same job as the star washer as I have in my aluminium steerer? i.e it sits inside the steerer tube itself and is pressed against the tub, thus giving something for the headset top cap to screw in to?

Is a star washer inadequate for carbon as it concentrates its expansive force over too small an area?

 

[lpretro1]

Yes. The bung does the same as a star nut. You cannot use the star nut as the metal tags would dig into the carbon fibre and damage it. The bung expands over a wider area and spreads any load on the carbon too. But they mustn't be overtightened when installing it or it can deform the carbon.

 

[Hawk]

Thankyou very much