Originally Posted by FBinNY

OK, by bellmouth I mean the flaring or enlargement of the end of the head tube. Think of the end (bell) of a clarinet or trumpet (though obviously much smaller).

When a mtn bike is ridden hard the continual pounding on the fork transfers to the inside of the headtube by way of the headset. It's the same as if you took a ball peen hammer to the inside end of the tube. The continual pounding stretches the metal making the inner diameter larger until the headset is no longer secure.

Now, with less force holding it, the head cup can move in the frame. It doesn't matter how tight you make the headset, since the movement is between the cup and frame. Since yours is only a slight creak, and not any serious (visible) movement, I venture that you can solve it by using a bearing retaining adhesive when pressing the headcup, or possibly by painting the lip of the cup.

If you have trouble understanding, you might print my posts and bring them to the shop for their consideration.

fb