The headset is the last part of a bike to be tackled in my self-education. I have built many bikes, converted some, but the frame always had a pre-installed headset. Having built a solid headset press out of allthread, washers and nuts, I set out to press the cups into the headtube. And then, trouble.

A 1 1/8" threadless setup quickly turned into a...mystery. I thought it was as simple as matching steerer tube diameter, but when testing the cups in the head tube, I discovered they are too small by a significant margin. I measured the inside diameter of the headtube and came out at 1 5/8" - half an inch in difference. The headtube on the 2007 GT Legato frame looks just like all of my other 1 1/8" bikes, so I am obviously missing something. All of the parts for the headset are accounted for, but since the cups are so much smaller, there's nothing to 'press': It just sort of sits in the headtube looking stupid, like the person installing it.

I know there are standard, integrated and 'Aheadsets', so I'm off to read what I can find, but I am not finding what I need on the Googlenet. Any help from this crowd would be much appreciated.